Long-distance triathlon tips

The bare minimum: 8 h/week

You can finish an Ironman on 8 h/week, provided you already have a solid endurance base (a marathon or a 70.3 under your belt). Below that, the risk of in-race muscle breakdown rockets, and the 3.8 km open-water swim turns into a leap of faith.

The sweet spot: 10-13 h/week

This is the range where most serious amateurs prepare an Ironman without sacrificing family or work. Typical split: 3-4 h biking (including a long ride of 4-6 h on peak weekends), 3-4 h running (with a long run of 2-3 h), 2-3 h swimming (3 sessions).

The real gap between athletes isn't peak weekly volume : it's CONSISTENCY: 20 weeks at 11 h crushes 12 weeks at 14 h with two weeks of interruption.

Beyond 14 h: who's it for?

Beyond 14 h/week, you're in podium-chase or Kona-qualifier territory. It's doable but requires 8 h+ sleep, structured nutrition and careful fatigue management. Plenty of "finishers" get hurt thinking more = better.

Remember: volume doesn't make you finish : the consistency of your volume does.

Rule 1: max +10% per week

This golden rule comes from sports physios. Beyond a 10% weekly increase in long-run duration, injury risk (periostitis, Achilles tendinitis, plantar fascia) doubles for every additional 5%.

Concrete example: if you ran 1 h 30 this week, target 1 h 40 next week, not 2 h.

Rule 2: stick to Z2

The long run has ONE goal: build your aerobic base. Not speed, not threshold. Cruising in Z2 (conversational pace, low BPM) costs 70% less fatigue than Z3 and leaves you fresh for the week's intensity session. You can add 10-15 min "progressive" at the end if you feel strong : never more.

Rule 3: deload every 3 weeks

The 3:1 ratio (3 progressive weeks + 1 deload week at -30%) is the grammar of every solid plan. Skipping the deload piles up "residual fatigue" that you pay back hard in the next 4-6 weeks. The longer your race (IM), the less optional the deload becomes.

Remember: the deload isn't a gift, it's an investment.

Why: the "concrete legs" feeling

When you dismount the bike and start running, the blood that was feeding your cycling quads has to redistribute to the running muscles (hamstrings, calves). That takes 5-15 min of painful transition where your legs refuse to obey. That's the "concrete legs" feeling.

The brick exposes your nervous system to that transition in training so it knows the pattern and doesn't panic on race day.

Three useful formats

1. Short brick ("run-off"): 60-90 min Z2 bike then 15-30 min Z2-Z3 run. Place 1×/week in build phase, moderate intensity. Goal: T2 sensation + stride opening.

2. Long brick ("mini-IM"): 3-4 h bike + 1-1h30 run. Place 1×/month in peak, NEVER more than 2× in the whole cycle. It's the pacing + nutrition rehearsal. Cost: 7-10 days of perceived recovery.

3. Intensity brick: threshold bike intervals (4×8 min Z4) then 10-15 min smooth Z3 run. Teaches you to run with an already-loaded heart.

The trap: transition too long

If you take a 10-15 min pause between bike and run (shower, snack, waiting), you miss the brick effect: your body has already redistributed the blood, you're not training the transition any more. Aim for 2-5 min max between "bike racked" and first running step.

Ideal: lay out shoes + visor + bottle BEFORE leaving for the bike, then string them together directly.

Why 3 sessions minimum

Swimming is a TECHNICAL sport before being an ENDURANCE one. Your progress depends on neuro-muscular stimulation frequency: you learn to "feel the water" only by getting back in often. Under 3×/week, your body "forgets" between sessions.

IM coach data: 2-session/week athletes plateau above 1:25/100 m. At 3 sessions, drop to 1:15-1:20 in 6 months. At 4 sessions, sub-1:10 reachable for most non-swimmer beginners.

Standard 3-session/week format

Session 1 : Technique (45-60 min): drill sets of 25-50 m (catch-up, finger-drag, fist swim, 3-6-3) + main set in short intervals 50-100 m with rest. Focus = motion, not clock.

Session 2 : Aerobic endurance (60-75 min): 3-5×400 m or 2-3×800 m at Z2 pace (conversational if you swam backstroke). This is the session that builds the capacity to do 3.8 km on cruise control.

Session 3 : IM-specific (60-90 min): long continuous 2000-3000 m at IM target pace, or pyramid 100-200-300-400-300-200-100 m at moderate pace. Once a month, in a lake with wetsuit if possible.

When to step up to 4-5 sessions

Stepping up to 4 sessions is only worth it if:

1. You target an IM swim time <1:05 (sea/lake varies ±10% so the window is narrow)
2. You're a former competitive swimmer wanting to regain that level
3. You're seeking a tactical edge in the pack (first out of the water in your wave)

Otherwise, keep 3 solid sessions and invest the saved time on the bike (where you can gain 20-30 min, vs 3-5 min on the swim). Pure return-on-time math.

Duration progression: the +15 min rule

You raise your long bike by 15 minutes per week maximum during the build phase. Cap at 5 h for a 10-13 h/week athlete, 6 h for a 14 h+ athlete.

Realistic IM progression starting from a 2 h long bike:

• Weeks 1-4: 2 h → 2:15 → 2:30 → 2:45 (recovery week at 1:45)
• Weeks 5-8: 3 h → 3:15 → 3:30 → 3:45 (recovery week at 2:15)
• Weeks 9-12: 4 h → 4:15 → 4:30 → 4:45 (recovery week at 2:45)
• Weeks 13-16: 5 h → 5:15 → 5:30 (peak) then taper.

The recovery week (every 4 weeks) cuts the long bike by 30-40%. It's what locks in the adaptations. Skipping it = plateau guaranteed.

Intensity: not tempo, not super easy either

The long bike primarily targets Zone 2 endurance (60-75% FTP, or RPE 4-5/10, conversation possible but not singing). That's where you build aerobic base, fat oxidation, and sport-specific muscular endurance.

Folding in 2-3 blocks of Zone 3 tempo (75-88% FTP, RPE 6/10) of 15-30 min AFTER h 2 simulates race-day fatigue and teaches your body to burn carbs WHILE ALREADY FATIGUED.

Avoid: doing the whole session in Z3-Z4. Tempting because it feels "productive". But you finish toast, miss the next day, and accumulate less IM-specific aerobic stress. An IM is ridden at ~70-75% FTP average : train at that intensity.

Brick run: 15-30 min to teach the legs

All long bikes over 3 h should be followed by a 15-30 min brick run at RPE 4-5/10. Not a "performance" run, a proprioception run.

Goal: your CNS learns to run with legs emptied by 3-5 h biking. That's exactly the T1 → IM marathon opening. Without these bricks, the first 5 km of an IM marathon is hell (10 km adaptation instead of 1-2 km).

From week 9-10 onward (long bikes 4 h+), at least 1 brick in 2 should include a longer jog (30-45 min) alternating 5 min Z2 / 1 min Z3, to simulate the race-day transition. No more : you pay in cumulative fatigue.

VO2max = ceiling for your other zones

Your VO2max is your MAXIMUM oxygen uptake capacity. You don't race an IM at 100% VO2max : but ALL your other zones (threshold, tempo, endurance) are computed as a PERCENTAGE of VO2max.

Improve VO2max by 5%, your threshold lifts ~3-4%, tempo ~3%, Z2 endurance ~2%. On a 10 h IM, that's 15-25 min of potential gain without changing anything else.

Analogy: VO2max is your engine's "displacement". You never run at 100% torque on the highway, but a 1.0 4-cyl and a 3.0 V6 don't consume the same for 130 km/h. Same idea.

Advanced amateurs (sub-10 IM) almost always have VO2max > 60 ml/kg/min. 11-12 h athletes often top out at 55-58 ml/kg/min. Ceiling = ceiling.

VO2max sessions that work

Classic formats (Norwegian double, 30/30 Billat, extended Tabata):

• 30 sec ON / 30 sec OFF: 8 × 4 min blocks. RPE 9/10 on ON, RPE 5 on OFF. Running only.
• 4 × 4 min (Norwegian method): 4 min at 90-95% HRmax / 4 min jog recovery. Cycling or running.
• 8 × 3 min on the bike (FTP+20-30 W) / 1 min easy. Triathlete favourite : also transfers gain to threshold power.

Target frequency: 1-2 VO2max sessions per week, NEVER more. Scheduled at the start of a hard block (week 1-2 of a 4-wk cycle), NEVER during taper.

Mandatory warm-up: 15-25 min progressive. Without it, you pollute the first 2 reps AND risk muscle strain or abnormal ECG.

When to avoid (and why)

Avoid VO2max:

• Beginner (< 1 yr regular endurance) : injury risk too high, ROI better elsewhere.
• 12 wk before IM, in "race specific" block : focus on threshold and specific endurance, not VO2max. VO2max stays 80-90% of peak for 8-10 wk without maintenance.
• Athlete in peak fatigue (CTL > 90, ATL > 80) : illness + strain risk.
• Women in pre-menstrual phase (week -1 to -3 of cycle) : reduced aerobic capacity, over-perceived effort.

VO2max scheduling: phase BASE 1 (16-12 wk pre-race), phase BUILD 1 (12-8 wk) : 1-2 sessions/wk. Then REMOVE in BUILD 2 and SPECIFIC, replacing with threshold / sweet-spot / tempo.

Don't fall into the "harder = better" trap. VO2max sessions are RARE quality work, not daily routines.

Why cadence matters on an IM

At equal power, riding at 75 rpm vs 90 rpm changes the SOURCE of fatigue:

• Low cadence (70-80 rpm): high pedal torque → recruits type-2 muscle fibres (the same ones you'll need to run). Cardiac economy (lower HR), but high muscular cost. You hit T2 with cooked quads : and you run badly.
• High cadence (90-100 rpm): low torque, high frequency → recruits aerobic type-1 fibres, HR runs higher but muscles are spared. You hit T2 "fresh legs". That's what you want on an IM.

The blunt rule: spinning at 90 rpm for 5-6 h makes you run better than grinding at 75 rpm for 5-6 h, at equal average power.

How to find YOUR target cadence

Home test on the trainer or flat road: ride 3 × 15 min at FTP × 0.75 (Ironman zone) at 3 cadences (80, 90, 100 rpm), 5 min recovery between blocks. Record average HR and muscle feel.

The right cadence = the one that MAXIMISES "light legs" feel WITHOUT blowing up your HR. For 80% of amateurs that's 88-92 rpm.

Factors that push higher (95+ rpm): you come from running (slow-fibre dominant), hot race (heat stress = need to spare muscles), hilly course (need responsiveness on climbs).

Factors that tolerate lower (82-87 rpm): you've been a road/long-tri rider for 5+ years (muscles adapted to torque), very flat course, headwind.

How to train cadence

1 session/week in winter/pre-season, 1 session/fortnight in peak:

• Spin-ups: 8 × 1 min at 105-110 rpm with 1 min recovery at 85 rpm, staying in Z2 (low power). Teaches your nervous system to spin fast without thrashing.
• Single-leg drills: 4 × 30 s per leg (on trainer only, safety), keeps effort clean and symmetric.
• Cadence ladder: 5 min at 80 rpm, 5 min at 85, 5 min at 90, 5 min at 95, 5 min at 100, at constant power (FTP × 0.65).

Remember: cadence is a NEUROMUSCULAR skill : it's trained over months, not on one ride.

Why Zwift beats road riding in winter

Three technical reasons:

• Effort density: 1 h on Zwift in structured intervals = ~50 min of time in target zone. On winter road riding, red lights, descents, urban slowdowns steal 30-40% of effective time. So 1 h Zwift = 1 h 30 road in equivalent training stress.
• Safety + warmth: zero crash risk, zero finger/toe frostbite, zero flat tyre at night. Across 4 winter months you also save 3-5 outdoor sessions lost to weather.
• Test consistency: your FTP test on Dec 15 is comparable to FTP on Mar 15 (same trainer, same resistance) : outdoor conditions mask your real progress.

Good to know: you can prep an IM on 100% indoor bike if you schedule 2-3 outdoor rides in the final month to re-adapt to real aero position + wind + traffic stress.

The typical 3 sessions/week protocol

Session 1 (Tuesday) : Threshold/Sweetspot 60-75 min:

• 15 min progressive warm-up (Z1 → low Z2)
• 3 × 12 min at 88-95% FTP (sweetspot), 4 min Z1 recovery
• 10 min cool-down Z1

Session 2 (Thursday) : VO2max/SST short 50-60 min:

• 15 min warm-up
• 6-8 × 3 min at 105-115% FTP, 3 min Z1 recovery
• 10 min cool-down

Session 3 (Saturday or Sunday) : Long endurance 2 h-3 h 30:

• Continuous Z2 (65-75% FTP), target cadence 88-92 rpm
• Optionally add 2 blocks of 20 min sweetspot toward the end if you're in build phase
• Films or podcasts to hold attention (solo Zwift gets miserable >2 h)

Weekly total: 4-5 h biking, ~4 TSS/min avg = stress equivalent to 6-7 h road.

Avoid: doing a 4th Zwift session "because you can". Above 5 h indoor/week, ergonomic toll piles up (posture loss, neck pain, cumulative demotivation).

Minimum gear so you'll actually stick with it 4 months

The minimum setup so you don't quit after 3 weeks:

• Smart trainer with ERG mode: Wahoo Kickr Core, Tacx Flux S, Elite Suito-T (~€500-800 new, €350-600 used). At all costs avoid non-connected "fluid rollers" (no precise power, no auto-structure).
• Powerful fan aimed at your torso: non-negotiable. Without a fan, HR climbs 10-15 bpm artificially at the same power (heat stress), sessions become inaccurate and unbearable. A €80 Lasko / Honeywell changes everything.
• Floor mat: protects your wooden floor from sweat (which CORRODES wood in a season). €30 at Decathlon.
• Towel + 1.5 L bottle within reach: you must hydrate without dismounting.
• Screen (tablet / TV) at eye level: otherwise neck tension after 2 h.

Honest total setup: €500-900 (used trainer + fan + mat). Cheaper than the high-end winter jacket + hat + gloves combo you'd need to ride outdoors at -5°C.

Zwift pitfalls to avoid

Pitfall #1 : "Social" group rides: you join a "group ride flat" at 2.5 W/kg, the group drops you, you push to hang on, you finish at 3.2 W/kg for 1 h. Was supposed to be Z2, you did Z3-4. Unplanned stress = 48 h compensation cost.

Pitfall #2 : Short "fun" races: a 30-45 min Zwift race easily averages 100-115% FTP. If your plan didn't program a quality session that day, you've introduced imbalance.

Pitfall #3 : Underestimating hydration: you sweat 2-3× more indoors than outdoors (no wind cooling). On a 1 h 30 session, target 750 ml-1 L of electrolyte drink + fruit or bar.

Pitfall #4 : Road bike position while prepping a time-trial IM: 100% sessions on standard road = bad adaptation. On your trainer in peak phase, mount your tri bike (aero bars) for at least 1 of every 3 sessions. Adapt aero position indoors, not in the race.

Why drills actually work

Drills don't build cardio fitness. They REORGANISE your neuromuscular stride pattern. Lab-measured effects:

• High cadence: you naturally shift from 170 spm (typical tired amateur) to 178-182 spm. High cadence = shorter ground contact = less braking = less energy lost.
• Foot landing under your centre of mass (flat or forefoot), not in front. Reduces shear stress on the knee and O2 consumption.
• Arms in sync: short clean arm movement stabilises trunk, saves O2 spent by postural muscles.
• More complete push-off (full hip extension, heel rising toward glute). You harness Achilles + soleus elasticity better : free in O2.

Measured gain: 2-4% running economy gain over 6-8 weeks of regular practice. That's huge. On a 4 h IM marathon, 3% gain = ~7 min.

The 10 min block : once a week

Insert 1× per week, either at start of run (post 5 min jog warm-up) or standalone 10-15 min another day. On track or flat grass, 30-40 m back-and-forth. Each drill 2 times.

1. High knees (30 m): knees up high, rapid cadence, arms synchronised. Feel: "running in place fast while moving forward slowly". 30 sec.

2. Butt kicks (30 m): heels rise toward glutes, slight forward lean. Engages soleus + hamstrings. 30 sec.

3. A skips (30 m): rhythmic skip, knee up ~90°, opposite arms synchronised. Trains coordination + hip extension. 30 sec.

4. B skips (30 m): A skip with leg extension before ground contact (as if pawing the track). More advanced. 30 sec.

5. Fast feet (20 m): tiny very fast steps, max possible cadence, moving forward slowly. Recruits fast fibres. 20 sec.

6. Carioca / side shuffles (30 m): lateral running crossing legs over. Hip mobility + balance. 30 sec each direction.

Total ~10 min with 30 sec recovery between each, walk back to start.

Remember: movement QUALITY counts 10× more than speed. A slow clean A-skip beats a fast sloppy one.

When to start, when not to push

Start in base or build phase (moderate volume, controlled intensity), ideally 8-16 weeks before your IM. You build the pattern, it "sets" in the following weeks.

Avoid:

• Peak phase (high volume, cumulative fatigue) : injury risk if pattern not yet stable.
• Taper week 1 (volume drops but intensity holds, not the time to introduce new stimulus).
• If you have active calf / Achilles / plantar fascia pain: skips and butt kicks load these tissues. Wait for resolution.

Practical routine:

• Weeks 1-4: 1 drill session/week, 5-7 min, pure quality.
• Weeks 5-8: 1-2 sessions/week, 8-10 min, at start of easy jog.
• Beyond: 1 maintenance session/week, 5 min, rest of the year.

Remember: an amateur runner who does 8 weeks of drills sees visible stride change. Cadence rises. Shins stop complaining. HR drops at the same pace. And ~5 min off the IM marathon. Free.

Pull-buoy: isolating the upper body

What it's for: a float between your legs that lifts your hips and neutralises kicking. You swim "arms only" with an ideal body position (aligned, horizontal).

Why useful for the triathlete:

• In IM you'll kick very little in open water (save legs for the bike). Learning to swim arms-dominant = directly transferable skill.
• You isolate technical work on the catch and arm placement without being disrupted by a bad kick.
• You can swim longer in controlled fatigue (arms alone less cardio-heavy than arms + legs).

When to use:

• 30-40% of your swim volume during the 6-8 technical weeks (base, build).
• Example sets: 6 × 100 m pull focusing on hand catch; 1500 m continuous pull at conversational pace.

When to avoid:

• Peak phase and the month before the race: you must regain a "complete" swim with kicking for adaptations.
• If your hips sink without a pull-buoy: that's a symptom to fix (core + head position), not something to mask by always wearing a pull-buoy.

Hand paddles: catch strength (handle with care)

What it's for: paddles strapped to your hands that enlarge your catch area. You move more water per pull = upper-body muscular force + catch sensation (hand proprioception).

Why useful: improves speed-strength in swimming, strengthens shoulder postural muscles, makes you feel where your hand "grips" water (technical fix).

How to choose: start with SMALL paddles (Finis Freestyler or equivalent, ~€25 : surface 1.5-2× your hand). Monster strength paddles 2.5-3× hand size = supraspinatus overload = shoulder injury risk in 4-6 weeks.

When to use:

• ALWAYS with a pull-buoy (otherwise a disorganised kick decompensates the pull).
• 100-400 m / session, no more. Inserted as a "force set" in a 1500-2500 m total session.
• Example: 4 × 100 m pull + paddles at 80% pace (focus long clean catch), 30 sec recovery.

When to AVOID:

• Any shoulder pain. This is a stimulus amplifier, not a treatment.
• Long fatiguing sets (1000 m+ continuous paddles = bad idea).
• More than 2 sessions/week. Tendon recovery needs 48 h.
• On a technically faulty arm pattern: you CRYSTALLISE the flaw. Fix technique first.

Ankle band: simulating open water

What it's for: an elastic loop that keeps your 2 ankles together, preventing kicking. More radical than a pull-buoy because there's NO artificial buoyancy. You MUST hold your hips up using core only.

Why useful for triathlon:

• The closest simulation of open-water swim in a wetsuit (which lifts your hips but doesn't give you a kick).
• Forces your core engagement and corrects trunk/head faults (lift your head = hips drop instantly).
• Cheap: a cycling band or knotted innertube does the job (~€0-5).

When to use:

• 1-2 sessions/fortnight during build and peak.
• On short sets: 6-8 × 25 m, or 4 × 50 m. No more than 200-300 m total with the band.
• As complement to a normal swim (not the whole session).

When to avoid:

• Beginner swimmer (you don't yet move forward without your legs : you'll panic).
• In group / crowded lanes: if you sink vertical, dangerous.
• If you have hip / ankle mobility deficit: you'll compensate via the back.

Remember: the ankle band is THE triathlon swim tool because it REPRODUCES the specific constraint of open-water IM. But also the hardest mentally : progress gradually.

The problem: "trust the algorithm"

Most modern AI coaching apps (TriDot, Humango, some TrainerRoad features) rest on models trained on millions of hours of data : which sounds impressive but leaves you facing a wall. When the app asks you to run 1h45 on Tuesday instead of the 1h30 you expected, you have no way to verify whether it's physiologically justified, or just a statistical artifact of the model.

The practical problem: if you feel the week is too loaded (work life, short sleep, cumulative fatigue), you don't have the levers to adjust while preserving plan coherence. You can only "obey or disobey". And you don't know whether you or the algorithm is right.

Worse: if you get hurt or your progress stalls, you don't have a testable cause hypothesis. The algorithm is black. No real debrief with a human coach, because nobody (not even the app's engineers) can tell you why that specific Tuesday, that specific volume.

The TriPaced principle: every decision has a citable source

TriPaced doesn't ask you to believe : it shows you. Every line of the plan comes from a named physiological rule, tested by decades of endurance literature, and identifiable in the app's code. No magic, no black box.

The 4 documented pillars:

1. Friel periodization (Joe Friel, The Triathlete's Training Bible, 7th ed. 2023) : Base / Build / Peak / Race / Transition, volume × intensity ratios by phase.
2. FTP / TSS / IF model (Allen & Coggan, Training and Racing with a Power Meter, 3rd ed. 2019) : Functional Threshold Power and Training Stress Score to quantify load.
3. 80/20 polarized (Stephen Seiler, Polarized Training 2010-2024) : 80 % of volume in easy aerobic zone, 20 % in high intensity, almost nothing in the in-between.
4. Friel long-run progression : weekly progression cap ≤ 10 % and a recovery week every 3-4 weeks.

When TriPaced programs a long run at 1h50 this week vs 1h40 last week, you can open the app, see the short explanation ("+10 % Friel cap, progression week"), and know it's rule 4 applying. Not an opaque model trained on someone else's data.

Concretely: FTP, taper, recovery week

Three concrete examples of how explainability changes your experience:

FTP (functional threshold power) : when TriPaced detects your new FTP from Strava, it applies the Coggan formula: FTP ≈ 0.95 × P_avg_20min on your best 20-minute effort in watts. Quality filters: Variability Index ≤ 1.05 (stable effort, not a fartlek), average cadence ≥ 80 rpm (rejects non-representative big-gear climbing efforts), ≥ 2 W/kg floor. If TriPaced does NOT propose a new FTP, it's because a filter tripped : and the app tells you which one. No "the algorithm has nothing for you today".

Friel taper : the 14 days before the race = gradual 20-30 % weekly volume drop while keeping 1-2 short quality sessions (5-10 min at IF 1.0). No abrupt stop, no "zero km in the final week". The rule comes from Mujika & Padilla 2003 ("Scientific bases for precompetition tapering strategies") and Bosquet 2007. Want to shift the taper by a day because of a work trip? The app knows exactly what to shift and what to preserve : the rule is readable.

Recovery week : every 3-4 weeks, load drops to 50-60 % of normal volume, intensity maintained. The frequency rule (3 vs 4 charge weeks) depends on your age (≥ 45 yo = 3-week cycle) and level (advanced sub-10 = handles 4 weeks). It's documented in the periodisation engine, not in a hash function trained on big data.

Upside: you can correct the plan, not just accept it

Explainability changes the power balance. If you get home from a work trip at 11 PM Sunday night and your 1h30 Monday session feels like a bad plan, you don't have to "negotiate with the algorithm". You know the Monday session is there to prime the block (Friel base/build rule), and shifting it by 24 h doesn't break the block : at worst it compresses Tuesday.

Same for race nutrition / hydration: TriPaced doesn't say "drink 750 ml/h" with no context. It says "500-1000 mg sodium/h (IM consensus, Reilly 2025)" and "weigh in pre/post training to measure your personal sweat rate". You can dose it yourself based on the day's conditions, because the rule is exposed.

It's also true if you get hurt: you can trace back, identify the session that tipped the balance (load × intensity × short recovery), and adapt the next block. With a black box, you can only stop using the app : and you learn nothing.

The 3-question test for your current plan

If you already use another tool, here are 3 questions to ask your plan to measure its explainability level:

1. "Why is this session at this intensity today?" : a good plan answers with a named rule ("polarized 80/20 : zone 2 primes the block"), not with "the model estimates it's optimal".
2. "If I shift this session by 24 h, what breaks?" : a good plan knows what depends on what (the long-run session depends on the 3-week chain, not on the individual session).
3. "What parameter do I change if I want to drop this week's load by 20 %?" : a good plan shows you the levers (loadFactor, early taper, anticipated recovery week) and their consequences on the next block.

If the plan fails on ≥ 2 questions, you're using a black box : regardless of the name it goes by ("AI coaching", "adaptive training", "machine learning powered").

The natural drift: the "moderate" grey zone

When an amateur triathlete starts running for 1 h, the pace that "feels right" is almost always between zones 3 and 4 (around ventilatory threshold 1). It's comfortable, it stings a little, you come home proud of "working hard". That's exactly the grey zone.

The grey zone is NEITHER low enough to develop aerobic base (mitochondria, capillarization, fat transport) NOR high enough to develop VO2max or lactate tolerance. It mostly develops cumulative fatigue : and gives the illusion of progress because times in that zone improve short-term (4-8 weeks), before plateauing.

Worse: at equivalent load, the grey zone generates ~2× more TSS than strict zone 2, so the recovery "bank" depletes fast. Typical result around week 8-10: degraded sleep, elevated waking HR, increasingly dull hard sessions, sometimes a minor injury (Achilles, hamstring, periosteum). It's the "moderate intensity trap" identified by Seiler in 2010.

The Seiler model: what elite endurance athletes actually do

Stephen Seiler, researcher at the University of Agder (Norway), publishes in 2010 an analysis of intensity distribution among the best Scandinavian XC skiers, biathletes, rowers and Nordic skiers: ~80 % of time in zone 1 (very easy, conversation possible), ~20 % in zone 3 (VO2 threshold or supra-threshold), practically NOTHING in zone 2 ("moderate tempo"). That's the polarized distribution.

The model has been replicated since in Kenyan marathon runners (Sandford 2017), pro cyclists (Lucia 2003 / Mujika 2012), elite IM triathletes (Plews 2014). It's also what Kipchoge does in running and Jan Frodeno in triathlon : confirmed in their interviews (no mystery in their training, it's just long, slow, and punctuated by very hard sessions spaced apart).

The Stöggl & Sperlich 2014 meta-analysis ("Polarized training has greater impact on key endurance variables than threshold, high-intensity, or high-volume training", Frontiers in Physiology) compares polarized vs threshold-training over 12 weeks: VO2max, time-trial, work-economy → polarized wins on all criteria. Treff et al. 2017 confirms on junior rowers. The science has been clear for 10 years. The general public ignores it.

The "sweet spot" and why it plateaus

Some popular apps (TrainerRoad notably) are historically built on sweet spot training = prolonged zone 3 at 88-94 % FTP. The pitch: "maximum return on training time, manageable fatigue, fast gains".

It's true short-term : over the first 6-12 weeks, especially for a beginner or someone returning from inactivity. FTP rises fast because you're training near-threshold tolerance, which is easily improvable. Then you plateau, because you haven't developed the aerobic base (lack of prolonged Z1-Z2) or the top end (lack of truly hard Z4-Z5).

The deeper problem: sweet spot maximizes stimulation at ventilatory threshold at the cost of chronically degraded recovery. For an amateur with 3-4 quality sessions per week, this means stacking 3-4 "moderately hard" sessions : when science recommends 1-2 truly hard sessions + everything else truly easy.

For an IM triathlete with 10-15 h/week, the opportunity cost is massive: every hour spent in the sweet spot grey zone is an hour that develops neither the bottom (mitochondria) nor the top (VO2max). It's the strongest scientific angle of attack against sweet spot, documented by Seiler in multiple reference podcasts (notably Empirical Cycling Podcast ep. 132 and Triathlon Taren 2024).

How to actually hold 80 % EASY (no cheating)

The 80 % easy is psychologically hard. The ego wants to "work properly". To actually hold it, 3 practical rules:

1. Objective metric on the easy session: use a HR zone + a power/pace zone, and stay under the ceiling even if "it feels too easy". Canonical check = talk-test: you should be able to say 5-6 words in a row without gulping air. If you can only say 3 → you're in the grey zone.

2. Cadence and pace discipline: on the bike, keep a high cadence (90-100 rpm) with an easy gear : that forces low watts. Running, accept walking the hills at the end of the long run if HR exceeds Z2. It's not weakness, it's strict polarized.

3. The ratio is evaluated over 4 weeks, not 1 session: you don't need EVERY session to be polarized : you need the AGGREGATE distribution over 4 weeks to be ~80 % Z1/Z2 + ~20 % Z4/Z5. On 12 h/week, that's ~9-10 h of Z1/Z2 and 2-3 h of hard intervals. The rest (cool-down, warm-up) counts in the 80 %.

A common mistake: counting "total time" instead of "time in zone". On a 4×5min VO2 interval session, the HARD time is 20 min, but the session lasts 1 h. The rest counts as EASY. That's what makes the 80/20 ratio achievable.

The 20 % HARD: 2 sessions per week, truly hard

The 20 % polarized does NOT mean "20 % of time in sweet spot". It means 1-2 high-quality sessions per week, truly above threshold : typically:

• Bike VO2max: 4×4 min at 110-120 % FTP, 3-4 min recovery between (Norwegian classic Seiler : used by Iñigo San Millán with Pogačar).
• Bike threshold: 2×20 min at 95-100 % FTP, or 3×12 min : hard but sustainable sessions IF the easy days have actually been easy.
• Run intervals: 6-8×800m at 5k VO2 pace (equal recovery) or 5-6×1000m at 10k pace.
• Run tempo+threshold: 25-40 min continuous at half-marathon pace (zone 3.5-4).
• Swim intervals: 8×100m at CSS (Critical Swim Speed) pace + 20s recovery, or 50/100/200/100/50 hard pyramid.

Golden rule: if you can do 2 hard sessions per week WITHOUT degrading the next one (sign: no quality drop, no elevated next-day HR) → you're well polarized. If you feel the 2nd hard session of the week is dull, either you do too much grey zone in the "easy", or you accumulate without recovery, or you underfuel. Diagnose case by case.

Base phase (8-16 weeks before the race): building the aerobic engine

The base phase is the least exciting but the most structural. Its goal: develop the aerobic base (mitochondria, capillarization, lipid enzymes, cardiac capacity at low output). Without a solid base, build sessions don't work : you cramp faster and recover more slowly.

Key sessions in base:

1. Long easy bike (Z1-Z2): 2h30 to 5h depending on level, strict Z2 HR maintenance (< 76% HRmax). No drift into the grey zone even on climbs : change gear. This is the session that most develops oxidative capacity and mitochondrial adaptations (Holloszy 1967, foundation of all modern endurance science).

2. Progressive easy long run: 1h30 to 2h30 in strict Z2, last third slightly accelerated but still aerobic. The "thirst long run" : too slow for the ego to be satisfied, long enough for slow-twitch fibers to be deeply stimulated.

3. Base technique swim session: 3000-4000 m at CSS -20% minimum (very easy), with technique work (kick drill, fingertip drag, catch-up). In base phase, swimming is technique first, intensity second.

What is NOT a priority in base: VO2max intervals (save for build), long bricks (cumulative fatigue risk too early).

Build phase (6-10 weeks before): developing specific power

The build phase increases specificity: you work on race pace, threshold and upper zones. Volume doesn't necessarily increase : intensity progresses.

Key sessions in build:

1. Bike threshold intervals: 2×20 min or 3×15 min at 92-95% FTP. The session that develops the maximum sustainable power threshold in racing : exactly what determines your IF (Intensity Factor) on the IM bike. Do once a week, never two days in a row.

2. Run threshold intervals: 4×10 min at half-marathon pace, or 3-4 km tempo. IM run threshold pace is ~10-15% below ventilatory threshold 2 : build sessions repeat it enough for the nervous system to memorize it.

3. The build brick: 1h30-2h bike at threshold (possibly including 2×20 min hard) + 30-45 min run at IM pace. The most specific session for an IM : trains legs to run after hammering the bike.

4. CSS swim: 6-10×100m at CSS pace (= swim threshold speed), 15-20s recovery. Develops the ability to hold race pace without blowing up. Alternate with long repeat sessions (200m, 400m at Z3).

Peak/specific phase (3-6 weeks before): replicating race conditions

The peak phase is the most demanding : and the most delicate. Goal: perform sessions very close to race conditions so the nervous, muscular and metabolic systems memorize the effort.

Key sessions in peak:

1. Bike race simulation: 4-5h at exact IM race pace (IF 0.68-0.73) without variation. No "I exceed threshold on climbs" : the simulation must be EXACTLY at planned race pace. Confirms nutrition, IF, long-duration mechanics.

2. Long peak brick: 4h bike at IM pace + 1h-1h30 run at IM pace. Done once or twice in peak at 4-6 weeks from the race. The session richest in feedback : if you cramp, overpace, or have GI issues, better to know here.

3. Short high-intensity VO2max maintenance sessions: 4×5 min at 106-110% FTP on the bike (once/week). Volume is lower than in build, but these sessions maintain the aerobic ceiling that "stabilizes" the threshold. Don't abandon VO2max in peak : just reduce volume.

4. Long peak run: 28-32 km at marathon pace +20-30 s/km. Never the week before a big brick : schedule 8-10 days before the first taper week.

What DISAPPEARS in peak: pure volume accumulation sessions (long 5h Z2 rides without specific structure). The base is built : maintaining it is optional, rebuilding it is dangerous.

Taper phase (2-3 weeks before): harvesting what was sown

Taper is not rest : it's the supercompensation phase. Volume decreases by 40-60% but intensity IS MAINTAINED. If you only do easy sessions before an Ironman, you arrive fresh but "asleep" : legs no longer know how to activate fast-twitch fibers.

Key sessions in taper:

1. A few short intensity reminders (D-14, D-10, D-7): 4-5×3 min at 105% FTP on the bike, or 3-4×1000m at 10k pace on the run. Short, targeted : the goal is activation, not loading.

2. Short long ride (D-10 to D-8): 2h-2h30 bike at easy IM pace + 20-30 min run. The last slightly long session before D-3 of total rest.

3. Swim maintenance: 2 light sessions/week of 1500-2000m in taper. Swimming tolerates pre-race freshness better than bike and run.

What NOT to do in taper: add sessions because "I feel like I'm regressing" (normal : that's supercompensation), try to "make up" for a volume deficit (3 weeks before the race = too late, adding volume now shifts supercompensation), change equipment (shoes, saddle, wetsuit : test everything in peak or before).

The classic taper feeling: heavy legs D-14 to D-10, then progressive lightening D-7, then energy boost D-3 to D-1. If the boost doesn't arrive at D-3, your peak load was too high or your nutrition insufficient (glycogen loading D-3 to D-1 = 8-10 g carbs/kg/day).

What exactly is zone 2?

Zone 2 corresponds to working below the first ventilatory threshold (VT1), where metabolism remains primarily oxidative (aerobic). In practice, it's the intensity at which you can hold a complete conversation without being out of breath : what Phil Maffetone calls the "MAF zone" (Maximum Aerobic Function).

In heart rate, zone 2 generally corresponds to 60-72% of max HR for non-elite triathletes, but this range varies by individual. The Maffetone method proposes 180 − age (± health adjustments) as the zone 2 ceiling: at age 27, that's 153 bpm. Below = zone 2. Above = you're entering the grey zone.

In bike power, Coggan zone 2 sits between 55-75% FTP (zone 2 out of 7 zones). But Iñigo San Millán (Pogačar's performance coach, UColo researcher) and other elite physiology experts prefer targeting the first lactate threshold (LT1) as the ceiling : typically ~65-70% VO2max, or ~70-80% FTP for a well-trained athlete. In practice: if your quads start to mildly "burn", you're already above zone 2.

In run pace, zone 2 is typically 65-80% of threshold pace (LT2). If your threshold pace is 4:30 min/km, your zone 2 running is around 5:40-6:55 min/km depending on your training level. Many triathletes find this too slow for their ego : and that's precisely the problem.

The real problem: the grey zone

The "grey zone" (Coggan zone 3, or zone between VT1 and VT2) is the most dangerous training intensity: hard enough to accumulate fatigue, not hard enough to get the VO2max adaptations of high-intensity sessions. This is where 60-70% of amateur triathletes spend most of their running training time.

Here's what typically happens: you set off for an "easy" zone 2 long run. After 15-20 min, your legs warm up and you naturally accelerate by 10-15 sec/km. Your HR climbs from 140 to 155 bpm. You tell yourself "this is comfortable, I can talk". But you're now in the grey zone, not Z2. On a 90-min long run, you just spent 65 min in the grey zone.

The consequences: you accumulate fatigue that compromises the quality of your next hard session, without getting the deep mitochondrial adaptations that only true prolonged zone 2 provides. Classic result: the triathlete doing "12h of training per week" but stagnating for 2 years because they're constantly fatigued without ever being truly hard.

Seiler's rule (polarized): in a well-polarized training week, 75-80% of volume must be below VT1 (zone 2 and below). The majority of studies on elite endurance athletes show this distribution. If you can't get 80% in Z2, your grey zone presence is too high.

How to precisely calibrate your zone 2

Gold standard method: lab lactate test → direct measurement of LT1 and LT2. Costs €150-300, available at sports medicine centers. If you can afford it before an IM preparation cycle, it's the most cost-effective investment.

Accessible method: conversation test → while running at a given pace, you must be able to hold a 5-6 word conversation WITHOUT catching your breath between each sentence. Not just "yes/no" : a real sentence. If you have to catch your breath mid-sentence, you're above Z2. Note the pace and HR at that moment: that's your ceiling.

Power method (bike): after a valid FTP test, start by targeting 65-70% FTP for zone 2 and adjust by feel. If you can hold a conversation, you're probably in Z2. If you're panting, you've passed LT1. Z2 rides should end with energy in reserve : no sense of having done a hard session.

The trap: don't use HR as the sole reference without adjustment → in hot weather (+28°C), your HR will be 5-10 bpm higher at the same effort. At altitude, same. After a bad night's sleep, your HR may be elevated by 5-8 bpm. In these conditions, lower your HR ceiling by 5 bpm or use pace/power as your primary reference.

Expected result: on a well-calibrated 90-min Z2 long run, you should arrive fresh (not euphoric, but fresh), capable of another hour if needed. If you're truly exhausted on arrival, you weren't in Z2.

How much zone 2 per week for an IM triathlete?

Minimum effective volume: to obtain significant mitochondrial adaptations (increased mitochondrial density, improvement in oxidative enzymes), studies suggest you need at least 3-4 Z2 sessions of 60 min per week. Below that, you're maintaining your base but not developing it.

Target volume for an Ironman: 8-15 h/week at build peak, of which 7-12 h in zone 2 (all disciplines combined). This is not a target to reach in week 1 : it's a progression over 4-6 months of preparation. A beginner will start at 6-8 h total with 5-6 h in Z2.

Where to put zone 2: swimming is particularly well-suited to zone 2 (good thermal dissipation, low joint impact). Long bike rides (2h+) are the main Z2 vehicles. In running, long runs (1h30-2h) must be 100% Z2 : days when they drift are no longer aerobic building, they're just fatigue.

Anti-J1 TrainerRoad "sweet spot": TrainerRoad's "sweet spot" approach (zone 3-4, 88-94% FTP) proposes accumulating hours at moderate intensity to "maximize adaptations per hour spent". The problem: this intensity space is precisely the grey zone. For an Ironman (9-12 h of racing), the deep aerobic base of zone 2 is irreplaceable. Sweet spot can complement build sessions, but it cannot replace Z2 blocks in the base phase.

Sources: Seiler & Tønnessen (2009), International Journal of Sports Physiology and Performance : elite athlete training distribution (80% low intensity). San Millán & Brooks (2018), Frontiers in Physiology : zone 2 and lactate as fuel. Coggan & Allen (2010), Training and Racing with a Power Meter, 2nd ed.

Normal fatigue, functional overreaching and OTS: three very different states

Understanding the three states lets you intervene at the right time : not too early (you miss the adaptation), not too late (you trigger the syndrome).

State 1 : Normal fatigue: after a big training week, you're tired. Performance drops slightly 24-48h after the load. One night of sleep or 48h of recovery is enough to restore performance. This is a healthy reaction : it's how training works. Hard → recovery → supercompensation.

State 2 : Functional overreaching (FOR): you accumulate hard blocks without sufficient recovery. Performance degraded for 1-2 weeks. With one intentional recovery week, you fully recover AND supercompensate. This is the state a "loading week" aims for. The boundary between FOR and OTS is subtle: FOR is intentional and planned, OTS happens when you ignore the signals and keep loading.

State 3 : Overtraining Syndrome (OTS): the short-term point of no return. Performance collapsed for >2 weeks with no external cause (illness, extreme life stress). Recovery takes 3-12 months depending on severity. OTS is rarer than you'd think in amateurs (it requires very high volumes over a long period), but unmanaged FOR is very common and can degenerate into OTS.

Key sources: Meeusen et al. (2013), European Journal of Sport Science : European consensus on overtraining definition and diagnosis. Halson & Jeukendrup (2004), Sports Medicine : systematic review.

The 7 warning signals to watch for

These signals can appear individually or combined. One isolated signal = monitor. Three or more combined signals = immediate load reduction.

1. Persistent stagnant or declining performance: you're doing the same sessions as before but times increase, power decreases, HR is higher at the same effort. Over 2+ weeks with no identifiable external cause.

2. Elevated resting HR: your wake-up HR (before getting up) is 5-8 bpm above your normal on several consecutive days. The morning after a long session, this is normal. Over 4-5 consecutive days, it's a signal.

3. Sleep disruption: you fall asleep with difficulty despite fatigue, or wake up early (4-5 am) for no reason. Elevated cortisol in FOR/OTS disrupts sleep : it's the opposite of normal fatigue (where you sleep deeply).

4. Irritability and low mood: people around you tell you you're "on edge". Overtraining affects the central nervous system and neurotransmitter production (serotonin, dopamine). This isn't "you're lacking mental toughness" : it's biochemical.

5. Repeated infections (colds, sore throats): chronic intense effort depresses the immune system. The post-exercise immune window (2-6h after a hard session) is well-known : but recurrent infections over several weeks indicate the system isn't recovering between sessions.

6. Loss of desire and enthusiasm: you dread sessions you used to love. This is one of the most reliable signals. Intrinsic motivation disappears : not because you're "lazy" but because the central nervous system in FOR/OTS is protecting the organism.

7. Persistent muscle soreness (prolonged DOMS): soreness lasting 72h+ instead of the usual 24-36h. The muscle doesn't recover at its normal rate.

HRV: the most reliable detection tool

Heart Rate Variability (HRV) measures the millisecond variation between each heartbeat at rest. High HRV = balanced autonomic nervous system = good recovery. Prolonged falling HRV = system under pressure.

Why it's useful: HRV changes before you subjectively feel the fatigue. It gives you 1-3 days advance on your sensations to anticipate a hard session or a recovery day.

How to measure: in the morning, immediately upon waking, lying down, for 3-5 min with a dedicated app (HRV4Training, Elite HRV, or Apple Watch/Garmin with their own HRV score). Measurement must be taken under the same conditions each day (same time, same position, before coffee).

How to interpret: don't look at the absolute value : it's individual and non-comparable between people. Look at the trend over 7-10 days. If your HRV is more than 8-10% below your 7-day average on 2+ consecutive days → load reduction. If it drops 15%+ in 1 day → active recovery that day.

Limitations: alcohol the night before, poor sleep, hormonal variation (female cycle) can vary HRV without any connection to overtraining. That's why you must look at trends, not isolated values.

Scientific validation: Plews et al. (2013), International Journal of Sports Physiology and Performance : HRV as a load management tool in triathlon athletes. Kellmann et al. (2018), European Journal of Sport Science : consensus on recovery monitoring.

Exit protocol: what to do when you detect 3+ signals

Week 1 : Massive volume reduction: reduce volume to 40-50% of your usual week. Intensity: Z1-Z2 only (easy to very easy), zero intervals. Goal: break the accumulation cycle.

Week 2 : Gentle active recovery: 5-6h total volume, still in Z1-Z2. If performance starts to return and fatigue dissipates → you were in FOR, not OTS. Good news.

If performance doesn't return after 2 weeks of reduction → consult a sports physician. Confirmed OTS sometimes requires 2-4 weeks of complete rest (no sport, not even jogging "to not lose fitness" : it's counterproductive). Return to training is gradual over 6-12 weeks with medical follow-up.

What you must NEVER do: "push through" a FOR hoping it'll pass. Or take 2-3 days of rest and return to the same load. Or try to make up the missed volume as soon as you feel slightly better.

Structural prevention: the best remedy is periodization with mandatory built-in recovery weeks (Friel: 3 weeks of load → 1 recovery week). If you never have a week with volume reduced by 30-40% in your plan, you're playing Russian roulette with FOR.

RPE (perceived exertion): the fundamental tool often overlooked

RPE (Rate of Perceived Exertion) is a scale of subjective effort, typically 1 to 10 (or the Borg 6-20 scale). In training: Z2 = RPE 4-5 out of 10 ("comfortable, I can talk"), Z3 = RPE 6 ("I can talk but in short sentences"), Z4/threshold = RPE 7-8 ("I can say a few words"), Z5 VO2max = RPE 9-10 ("almost impossible to speak").

RPE strengths:

• Works with zero equipment.
• Automatically accounts for all daily factors (heat, cumulative fatigue, life stress, early illness). If an effort feels harder than usual at a given pace, your body knows it before your watch does.
• Reliable for long Z2 sessions: if you can hold an easy conversation, you're in Z2 regardless of what your watch says.
• Correlates well with blood lactate in trained athletes (Borg 1982, Medicine & Science in Sports) : the higher your level, the more accurate your RPE.

Limits: hard to calibrate for beginners (everything seems hard). Doesn't allow exact session replication week to week. For high-intensity intervals, subjectivity can lead to going too hard or not hard enough.

Heart rate: precise but with important limits

Heart rate measures the cardiovascular response to effort. It's a good proxy of RELATIVE intensity (% of max HR) but is influenced by many extrinsic factors that actual effort doesn't control.

Strengths: good zone calibration tool if max HR is known. Useful for running (no simple power equivalent). Reliable in stable, well-controlled conditions.

Important limits:

• Cardiac drift: on a long session (>1h30), HR progressively rises 5-15 bpm at THE SAME power/pace, due to dehydration and blood redistribution to the skin. If you're pacing by bike watts or run pace, your HR at the end of the session will be higher than at the start : don't take it as a signal to slow down.
• Heat and altitude: HR is 5-15 bpm higher at the same effort in hot weather (+28°C) or at altitude. A "constant HR" session in cold weather will make you go faster than in summer.
• Individual max HR: formulas (220 − age, etc.) have a standard deviation of ±10-15 bpm. If your real max HR is 195 but the formula gives 183, all your zones are wrong.
• Temporal lag: HR responds to effort with 30-60 sec latency. For short intervals (<2 min), HR doesn't reflect real intensity at the peak of the interval.

When to use HR: Z2 and Z3 in stable conditions (running especially). As a recovery indicator (morning resting HR). For swimming (the only practical tool in the pool).

Power (bike): the gold standard for triathlon cycling

A power meter measures the mechanical energy actually applied to the pedals, in watts. It's the most precise and reliable measurement tool available for bike training.

Strengths:

• Immediate: no response delay like HR. To the second of a pedal stroke, you know exactly what intensity you're working at.
• Stable: power isn't affected by heat, altitude, fatigue, stress or dehydration (unlike HR). 250W in summer heat = 250W in winter (perceived effort is harder in the heat, but the power is the same).
• Repeatability: you can compare your power exactly week to week on the same segment.
• IM pacing: on an Ironman bike, power pacing (targeting constant 65-75% FTP) is the most reliable strategy to not blow up the marathon. HR-only pacing misses cardiac drift.

Limits:

• Cost: €300-700 for a quality meter (Garmin Vector, Assioma, 4iiii, etc.).
• Doesn't replace HR for running (no reliable, democratized running power meter).
• Doesn't account for cumulative fatigue: 300W on fresh Tuesday legs ≠ 300W on Saturday after a loading week : RPE diverges.

Without a power meter: GPS pace in running + RPE are valid substitutes for the vast majority of amateur triathletes. Don't feel obligated to buy a power meter if your training budget is tight. Consistency and periodization are worth more than an expensive meter.

How to combine all three on an Ironman

The optimal combination depends on available tools, but here's the recommended model:

Swim: HR not practical in racing. Use RPE (stroke cadence + breathing effort) + pace per 100m if you have a swim computer. Z2 swimming = you can "chew" a conversation between lengths (pool) or at the end of a crossing (open water).

Bike (with power meter): power as primary reference (targeting 65-72% FTP for a Full IM) + HR as verification (if HR climbs 10 bpm above your usual zone at the same power → you're in cardiac drift or early heat stress → reduce power). RPE = alarm signal if RPE > 6 at 65% FTP (you're probably dehydrated or it's too hot).

Bike (without power meter): HR + RPE. Aim for stable or slightly rising HR (cardiac drift is inevitable). If RPE > 6, slow down. Don't fight to hold a GPS speed on the IM bike : wind and elevation make speed non-representative of actual intensity.

Run: GPS pace (but watch out: no fixed pace target : start 5-10 sec/km slower than target pace and aim for a progressive acceleration over the second half) + HR to monitor drift + RPE to decide final adjustments. The rule: if RPE > 7 before km 15, you went out too fast.

Practical summary: for 95% of amateur triathletes, GPS watch with HR + calibrated RPE = sufficient. A power meter adds extra precision on the bike, especially for IM pacing. Don't over-equip at the expense of consistent training volume.

Why swim taper differs from run and bike taper

In running and cycling, taper mainly involves reducing volume while maintaining intensity. The goal: let muscle fibres regenerate and replenish glycogen without losing neuromuscular sharpness.

In swimming, a specific problem arises: swim technique degrades quickly if volume drops too low. Swimming is a highly technical activity : the "feel for the water" (proprioceptive sensation of water pressure on the hand and forearm) is built through repetition and lost within days without practice. A study by Costill et al. (1985) on competitive swimmers showed that 4-14 day rest periods degrade swim mechanics even in very experienced athletes.

Practical consequence: swim taper should never be a complete stop or a reduction to 20% of usual volume. Too aggressive a cut "breaks" the feel and you arrive at the race with clumsy swimming despite rested muscles.

Recommended swim taper protocol for triathlon

Research by Mujika & Padilla (2003) on taper in endurance athletes shows that a 40-60% volume reduction over 2-3 weeks, MAINTAINING session intensity and frequency, produces the best performances. Applied to swimming for an amateur triathlete:

3 weeks before the race:

• Last full volume week (or slightly reduced if the plan calls for it)
• Keep at least 3 sessions/week
• Focus: a few race-pace reps in longer sessions to calibrate feel

2 weeks before:

• Reduce swim volume by 30-40% (e.g.: from 10,000m/week to 6,000-7,000m)
• Maintain frequency: 3 sessions/week minimum
• Keep 1-2 short race-pace reps per session (e.g.: 4×100m at 70.3/IM pace)
• Reduce session length, not their structural intensity

Race week:

• 2-3 short sessions of 1,000-1,500m total
• Include short accelerations (6×50m descending pace) to activate neuromuscular pathways
• Last session: D-2 or D-3 maximum. No swimming at D-1 except 200-300m very easy to avoid shoulder fatigue

Most common swim taper mistakes in amateur triathletes

Mistake 1: stopping swimming completely 10-14 days before → Water feel lost, clumsy swimming despite rested muscles. The triathlete confuses "muscle rest" and "technical rest" : swimming doesn't need as much of the latter.

Mistake 2: too much swimming at D-1 week → Shoulder fatigue (deltoids, trapezius) felt within the first 500m of race morning swimming. In an IM where the swim serves as a warm-up, starting with tired shoulders is counterproductive.

Mistake 3: eliminating intensity during taper → Only doing Z1-Z2 sessions without any accelerations in the last 2-3 weeks. Result: the nervous system "goes to sleep" and you arrive at the race with good muscles but poor neuro-muscular connection.

Mistake 4: neglecting swim taper to focus on cycling and running → Common in triathletes coming from a running background. The swim remains the most technical segment : poor swimming unnecessarily stresses the heart from the start and can affect the other 2 disciplines.

Bonus point: the pre-race open water briefing

If you usually swim in a pool and your race is open water, the 2-3 weeks of taper are also the time to practice in race conditions:

• Deep water start (no wall touch): if you always swim with the wall at the end, you're not used to a deep water start. Practice at least 1-2 starts from the middle of the lane.
• Navigation (sighting): looking up at a buoy or landmark while swimming. Ideally 1 session in a lake/sea in the last 2 weeks to confirm that the sighting movement doesn't break your stroke.
• Wetsuit: if you use one (water < 24.6°C in IM EMEA most of the time) → 1-2 sessions in the wetsuit in the last 2 weeks to get comfortable with the extra buoyancy. The suit changes the water feel on your arms : better to discover this in training.
• Mass start: if this is your first IM, do a mental movie of the start: you'll be surrounded by hundreds of athletes, there will be kicks and arm hits, it's normal. Start slightly to the side if you're a beginner to avoid the centre of the scrum.

What FTP is and why it's the key number

FTP (Functional Threshold Power) is defined as the maximum power you can sustain for approximately 60 minutes in a stable fatigue state : neither rising nor collapsing. In practice, it corresponds to lactate threshold 2 (LT2), the point where lactate production begins to exceed clearance capacity.

Why it's central:

• All your cycling training zones are calculated as a percentage of your FTP (Coggan/Allen model)
• A power meter without a calibrated FTP is useless: the numbers mean nothing
• FTP evolves with training: a beginner athlete can see it improve by 10-20 W in 8-12 weeks of targeted work

Unit: watts (W) or more commonly W/kg (power normalised by body weight). An amateur triathlete preparing a Full Ironman typically sits between 2.5 and 4 W/kg. An elite athlete: 4.5-5 W/kg.

The two FTP tests you need to know

20-minute test (classic Coggan method):

1. Warm up 10-15 min progressively
2. Maximal sustained 20-minute effort (on a smart trainer or flat, safe road)
3. FTP = 95% of your average power over 20 min (empirical coefficient compensating for the duration effect: 20 min is not 60 min)
4. E.g.: 250 W average over 20 min → estimated FTP = 237 W

Ramp test (INSCYD / alternating protocol):

1. Warm up 10 min
2. Increase by 20 W every minute until failure
3. FTP ≈ 75% of the last completed minute (or peak power reached, depending on protocol)
4. Shorter (~20-30 min total), less anxiety than the 20-min test, good correlation for cycling-oriented athletes

When to retest: every 4-8 weeks in the building phase, or after a recovery block. An athlete who hasn't retested in 3 months of serious training probably has an underestimated FTP.

The 7 power zones according to Coggan/Allen (2019)

The reference model for structured cycling (Allen & Coggan, Training and Racing with a Power Meter, 3rd ed.) defines 7 zones:

For an Ironman: 80-90% of bike volume should be in Z2 (long aerobic endurance). Quality sessions target Z3-Z4 (IM bike pace = Z3 for most amateurs).

Configuring your zones in an app or on your device

Step 1: enter your FTP in the app (Garmin Connect, Wahoo, Zwift, etc.). Most platforms offer an "FTP" field in the cycling profile. Never leave the default value (often 200 W or the manufacturer's estimate).

Step 2: check the zone model used by the platform. Garmin uses 5 zones (slightly different from the 7-zone Coggan model). If your coach prescribes Z4 Coggan and your watch has 5 zones, you need to convert : or sync the names with your coach.

Step 3: validate with a test ride after configuration. 60-min Z2 ride: you should be able to hold a conversation (sentence test), never panting, finish fresh. If you arrive exhausted → your Z2 is too high → your FTP is underestimated.

Step 4: reconfigure after every FTP test. Many athletes test at the start of the season and forget to update. In June, your FTP may have improved by 15-20 W vs January : all your zones must be recalculated.

Dressing right: the over-insulation trap

The #1 trap is dressing like you're going for a hike. On the bike, the body heats up fast but stays exposed to wind. Rule of thumb: you should feel slightly cold the first 5 minutes. If you're comfortable at the start, you'll sweat too much mid-ride, then cool down and come home with a chill.

Recommended layers by temperature:

• +10 °C: long bib tights, long-sleeve jersey, light gloves, windproof gilet.
• +5 to +10 °C: thermal bib tights, breathable base layer, thermal windproof jacket, thick gloves, shoe covers.
• 0 to +5 °C: as above + neck warmer, balaclava under helmet, waterproof over-gloves. Head and extremities account for 40 % of body heat loss.
• Below 0 °C: use the indoor trainer. The risk of black ice far outweighs the benefits of an outdoor session.

What's always forgotten: the descents. A 10-min descent at 40 km/h in 5 °C feels like -10 °C. Keep a compact gilet in your back pocket for long descents.

The winter long Z2 ride: duration and format

In winter, the goal is to consolidate aerobic base, not to chase watts. Zone 2 (60-75 % of your FTP) for 2-4 h: this is where the diesel engine is built. Base work is boring, but it's irreplaceable: endurance athlete research shows 80 % of volume in Z2 is the foundation of all elite athletes (80/20 polarisation).

Practical format for a 3 h winter ride:

• 15-20 min progressive warm-up Z1 → Z2
• 2 h 20 in steady Z2 (if you can hold a short conversation, you're in the right zone)
• 15-20 min Z1 cool-down

The group trap: in a winter group ride, the pace often drifts toward Z3-Z4 on climbs through implicit competition. Not necessarily bad, but if your plan calls for pure Z2, better to ride solo or with partners agreed on the session goal.

Frequency: 1-2 long rides per week is enough. The rest of your volume can go on the indoor trainer (short intervals, technical quality).

When to use the indoor trainer instead of the road

The indoor trainer isn't a soft option : it's a strategic tool. It outperforms the road in several situations:

Use the indoor trainer for:

• Short sessions <1 h with quality intervals (impossible to hold Z4-Z5 outdoors with traffic lights, descents, cars)
• Dangerous conditions: freezing rain, snow, hail, complete darkness
• Technical recovery: cadence drills at 100+ RPM, one-leg drills
• Very short days (winter, 6 AM start = riding in full darkness)

Prefer the road for:

• Long Z2 rides of 2 h+ (the monotony of the indoor trainer past 90 min is a real mental barrier)
• Muscular adaptation to vibration and real-world position
• Practising nutrition and thermal management

Indicative winter ratio: 60-70 % indoor / 30-40 % outdoor. This ratio reverses in spring as days lengthen and races approach.

Why strength training genuinely makes a difference in long-distance triathlon

Three main mechanisms:

Power and movement economy. Maximal strength determines sub-maximal economy. A cyclist with a heavy squat has better economy at 200 W than someone of the same weight without strength training : their recruited fibres at that wattage represent a lower % of their max. Same logic in running: a better strength-to-weight ratio reduces the metabolic cost of each stride.

Injury prevention. Triathlon stacks 3 unilateral sports (swimming creates a shoulder/back imbalance, cycling closes the posterior chain, running overloads hamstrings and calves). Strength training balances these adaptations and reinforces compensation zones: glutes, posterior chain, hip stabilisers.

Muscular endurance under fatigue. Hours 8-10 of an Ironman recruit muscles in a pre-fatigued state. A strength base delays running form breakdown (cadence drop + shortened stride length) : the main marker of a failed IM marathon.

Friel's logic: 4 phases, not one generic session year-round

Joe Friel (The Triathlete's Training Bible, 7th ed. 2016, ch. 13) divides strength work into 4 phases aligned with annual periodisation:

TriPaced labels this PC on your plan ("Strength PC :" sessions). Friel sometimes calls it PE (Power Endurance) depending on edition : same pre-race window.

Classic mistake #1: doing MS year-round → injury or chronic overtraining. Classic mistake #2: stopping strength in Build/Race → losing useful strength during the season.

Friel is explicit: in-season (Build + Peaking), minimum 1×/week maintains your acquired strength base. Zero sessions = detraining in 4-6 weeks.

AA phase: laying foundations without injury (8-12 winter weeks)

AA is the most underrated phase. Most triathlete strength injuries happen when jumping straight into MS after a break : tendons haven't had time to adapt.

AA characteristics:

• High volume (3 sets × 20 reps), low loads (60-65% 1RM)
• Goal: no muscle, no fatigue → vascularise tendons, reinforce connective tissue
• Frequency: 2-3×/week (3× for a weak base, 2× for an experienced athlete)
• Duration: 4-8 weeks before moving to MS

Priority exercises in AA:

• Squat or leg press (quad/glute/lower back)
• Hip hinge (Romanian deadlift, kettlebell swing) : posterior chain
• Horizontal pull (seated row, resistance band pull) : shoulder balance
• Plank and anti-rotation core (Pallof press)

Progression signal: if 20 reps feel easy at week 3, increase load by 5% and verify technique stays perfect. Never increase load AND volume simultaneously.

MS, PC and SM phases: staying strong without tanking triathlon training

MS phase (Maximum Strength) : Base 2 and Base 3: This is where you build raw strength. Heavy loads (80-90% 1RM), low reps (3-6), long rest between sets (3-5 min). Maximum 2×/week frequency : beyond that, neuromuscular fatigue spills into cardio sessions. The week's overall RPE must remain manageable: if you struggle in the pool the morning after a heavy MS session, the load is too high.

PC phase (Power Conversion) : 5 to 8 weeks before race: You convert MS strength into tri-useful power (plyometrics, moderate-explosive loads, 10-15 reps). This is the window Friel sometimes labels PE depending on edition. TriPaced prescribes "Strength PC :" sessions with ballistic work and fast tempo. 1-2×/week is enough; the goal is no longer gaining strength but making it available under fatigue.

SM phase (Strength Maintenance) : final Build and Peak (≤4 weeks before race): The goal is to keep MS gains without accumulating fatigue. Moderate loads (70-80% 1RM), 8-12 reps, 2 sets is enough. Minimum 1×/week according to Friel : two SM sessions during a heavy Build week is often too much.

Practical rule to avoid strength/triathlon conflict:

• Schedule strength sessions on the same day as a short or recovery cardio session : not the day after a long run or long ride.
• Never do MS the day before or after a brick or VO2max session.
• Recovery weeks: skip strength or drop to light AA (50% load, 2×15).

Home vs gym: what TriPaced adapts automatically

The MS phase in particular needs heavy loads : hard to replicate with just resistance bands. TriPaced knows this and adapts exercises to your equipment inventory.

With a full gym (rack, dumbbells, cable) :

• AA: squat + leg press + cable row + barbell bench press
• MS: heavy squat + barbell RDL + seated cable row + leg press
• SM: dumbbell circuit + uni-lat glute work

At home (dumbbells + pull-up bar + bands) :

• AA: goblet squat + dumbbell RDL + pull-ups + core work
• MS: available load limits true MS : TriPaced prescribes weighted Bulgarian split squat + hip thrust with barbell + weighted pull-ups to partially compensate
• SM: dumbbell circuit 3×10, resistance via load + band

When equipment limits : if you have no rack or barbell, true MS phase is hard to achieve at home. Two options:

1. Get a 2-3 month gym membership for the AA→MS phases, then finish SM at home.
2. Accept a sub-optimal MS phase (Bulgarian split squat at max dumbbell weight + max-load hip thrust) : fewer gains but no injury.

TriPaced automatically configures exercises based on your mode (gym or home) and the items ticked in your equipment inventory. Adjustable anytime in settings.

Why legs feel heavy at T2

After 3-5 h of cycling, your hip flexors and quads are in a state of specific neuromuscular fatigue: slow-twitch fibres (Type I) have contracted repeatedly through the same joint angle. Switching to running : which demands full hip extension : creates a neuromuscular mismatch: the brain must 'reprogram' the locomotion motor pattern, and that takes 2-5 minutes of uncomfortable running.

Coaches call this the 'brick feeling'. It's not an injury : it's an adaptation lag. With training, it shortens dramatically.

How to structure a brick session

The basic rule: the run must start within 5 minutes of finishing the bike (10 min max for shoe change). Any longer break reduces the sought adaptation effect.

Beginner format (introduce from week 2 of training):

• Bike 45-60 min at Z2 → Immediate run 10-20 min Z1/Z2 (accelerate slightly in the last 2 minutes)
• Frequency: 1×/week

Intermediate format:

• Bike 90-120 min at Z2/Z3 → Immediate run 30-45 min Z2 (progressive)
• Frequency: 1×/week, occasionally 2× during build

Pre-race format (3-4 weeks out):

• Bike 3-4 h at race pace → Run 30-60 min at target marathon pace
• Frequency: 1-2× to validate pace feel

Error #1 to avoid: running too fast in the brick (Z4 on the run). The goal is neuromuscular, not cardiovascular. Keep paces conservative.

Frequency and plan integration

One brick per week is the norm during base and build phases. During peak phase (last 6-8 weeks), you can go to 2× if recovery keeps up.

Ideal weekly placement: Saturday or Sunday (long day with long bike). Following a long bike ride with 15-30 min run is more effective for brick-feeling than two short separate sessions.

What NOT to do: a brick after a leg strength session or the day after a long run. Specific muscular fatigue doubles tendon injury risk.

Progression marker: the 'brick feeling' should decrease week over week. If you're still running on wooden legs after 5 minutes after 8 weeks, increase brick frequency or check your bike pace (too intense = too much fast-twitch glycogen depletion).

Why you veer off course (and what it costs)

Without visual reference, nobody naturally swims in a straight line. Side dominance (arms, legs, head rotation), swell, current and even start anxiety all create progressive drift. Open water studies show amateur triathletes swim an average 15% extra distance over a 1500 m.

On an Ironman (3.8 km swim), 15% drift = 570 m extra : roughly 10-15 minutes lost in the water. On a 70.3 (1.9 km), that's 285 m extra ≈ 5-8 minutes.

Add the energy cost: constantly correcting trajectory (pulling, sprinting to catch a group) burns more than holding a straight course from the start.

Most common drift causes:

• Systematic unilateral head rotation (always breathing on the same side)
• Asymmetric pull (one arm pulls harder than the other)
• Fan kick (dominant leg deflects the trajectory)
• No clear visual references established before the start

Sighting technique: the crocodile method and optimal frequency

The crocodile method (recommended):

1. During the arm recovery, just before the hand enters the water, lift only the eyes above the surface : like a crocodile : without lifting the entire head.
2. Spot the buoy or landmark (1-2 seconds max).
3. The head returns to neutral position, breathing happens to the side ON THE NEXT CYCLE (not simultaneously with sighting : this overloads the neck).

Technique to avoid: full frontal head lift. Raising the whole face out of the water forces hips to sink, increases hydrodynamic resistance by 30-40% on that cycle, and fatigues traps and neck over distance.

Recommended sighting frequency:

• Choppy water or race start (jostling): every 6-8 strokes
• Calm water, stable trajectory: every 10-15 strokes
• If drafting in a well-positioned group: reduce to 15-20 strokes as the leader sights for you

Landmarks to identify BEFORE the start:

• The main buoy for the next section (large, brightly coloured)
• A fixed terrestrial point behind the buoy (steeple, pylon, building) : more stable than a buoy in swell
• The cap colour of fast swimmers ahead of you

3 drills to integrate sighting into training

Drill 1: pool sighting (15 min) Swim normal lengths, then add a sight every 10 strokes : look up at the pool clock or a point at the far end of the lane. Goal: make the movement automatic without breaking the breathing rhythm.

Drill 2: swim with eyes closed (5 min) In the pool, close your eyes for 5-10 strokes. See how far you've drifted. If you regularly touch lane ropes, your pull is asymmetric : work on this with a swim coach or underwater video.

Drill 3: open water sessions (at least 4-6 before target race) Add 20-40 min lake or sea sessions before race season. Choose landmarks (buoy, lighthouse, shoreline) and swim toward them while practising crocodile sighting. Test different conditions: light swell, sun ahead (lower the cap slightly before start if sun is directly in your eyes at buoy 1).

Advanced drill: draft + sight Swim behind a partner staying in their feet (30-50 cm). Practise sighting by slightly tilting the head to the side rather than full frontal : useful in a dense pack during races.

The 3 main protocols and their logic

1. 20-minute test (classic gold standard) Protocol: after a 10 min warm-up + 5 min activation effort at high intensity then 5 min recovery, perform a 20-minute all-out effort. FTP = 95% of average power over 20 min (correction factor for the gap between 20 min VO2max effort and sustained 60 min effort).

Advantages: universal protocol, easy historical comparison, well documented in Coggan & Allen literature. Limitations: result is very sensitive to pacing : starting too hard = collapse, underestimated value; starting too easy = also underestimated. Requires experience to calibrate the effort correctly.

2. Ramp test (progressive protocol, 1 min per step) Protocol: start at low power (~50% estimated FTP), increase by 20 W each minute until failure. FTP = 75% of maximum power reached at the last completed step (Seiler factor based on empirical data).

Advantages: quick (15-25 min total), less pacing required, less mentally taxing. Ideal mid- or end-of-block without adding major fatigue. Limitations: favours high anaerobic capacity profiles (sprinters) : may overestimate FTP for athletes with high anaerobic power. Less reliable for triathletes with a very aerobic/endurance profile.

3. 8-minute × 2 test (Coggan alternative) Protocol: 2 × 8 min all-out efforts separated by 10 min recovery. FTP = 90% of average power over both efforts.

Advantages: good compromise between time constraint and accuracy. Lower risk of pacing failure than a 20 min test. Limitations: still not widely used, fewer comparison references available.

Which protocol specifically for a triathlete?

The triathlon context changes the rules. A triathlete rarely tests at 100% freshness: swimming and running load impact the legs. Some practical guidance:

If you're new to power zones → ramp test. Less risk of misjudging the effort, accurate enough to calibrate zones. Do it at the start of a base cycle (rested body).

If you have ≥ 1 year training with a power meter → 20 min test, after at least 2 days of complete recovery (no heavy swim or run the day before). Perform after 48h clear of intense training to get a reliable result.

If you're mid-plan without time to rest → ramp test. Less residual fatigue post-test, training can resume the next day with adjusted loads.

For triathletes with a pure endurance profile (highly developed aerobic engine): the ramp test may underestimate your real FTP. Prefer the 20 min test or validate with a controlled long ride (observe the normalised power (NP) sustainable over 60-70 min in zone 3-4).

Recommended frequency:

• Base phase → test at phase start (initial calibration)
• Base→build transition → retest (FTP often rises 3-8%)
• 4-6 weeks before race A → final retest (also serves as a psychological simulation session)
• Never during peak/taper phase (legs aren't available and the stress adds fatigue)

Test conditions and classic mistakes

Optimal conditions:

• Smart trainer (recommended): controlled temperature, no traffic, identical test reproduction. Fan mandatory : 5°C higher = 3-5 W less at iso-cardiac power.
• Outdoor if no smart trainer: choose a long, consistent climb (avoids braking and wind variations). Accept ±5% additional variability.
• Always the same power meter (don't compare a Garmin Vector with a Quarq : values can differ by 3-8% depending on calibration).

Classic mistakes to avoid:

• Testing after a heavy training week without recovery → underestimated FTP
• Too aggressive pacing in the first 3 minutes → collapse at minute 10, failed test
• Testing the day after a long ride → same outcome
• Using FTP estimated by Garmin/Wahoo without ever testing → auto algorithms are accurate to ±15%, insufficient for fine zones
• Rounding up to flatter yourself → all zones too high, chronically too-hard training, overtraining risk

After the test: update all zones in your training app (Garmin Connect, TriPaced, Wahoo) immediately. An FTP not updated for 6-8 weeks = misaligned zones = partially invalid plan.

The 4 phases of a structured triathlon season

Phase 1 : Base (fundamental aerobic) Duration: 8-12 weeks | Goal: build the base aerobic engine. In zone 2 (60-72% max HR / < VT1), mitochondria multiply, capillary density increases and slow-twitch fibre recruitment efficiency improves. This is the phase where 80% of sessions are 'easy'. The temptation is to go too fast : too hard in base = insufficient foundation, progress stagnates later. Phase-end signals: resting HR drops 3-5 bpm, easy paces improve without extra perceived effort, long sessions recover better.

Phase 2 : Build (specific load development) Duration: 6-10 weeks | Goal: develop specific energy systems (threshold, VO2max). Introduction of threshold sessions (zone 3-4), long intervals (zones 4-5), long bricks. Volume still present but intensity increases. The 80/20 ratio (polarised) is maintained : no more than 20% of volume above VT1.

Phase 3 : Specific / Peak Duration: 3-4 weeks | Goal: simulate race conditions at target intensity. Long sessions at Ironman pace/power, long bricks (90 min bike + 30-40 min run at target pace), open water swim repetitions. Volume slightly reduced, specific intensity maximal. Performance testing possible here (FTP ramp test, 1500 m swim time trial).

Phase 4 : Taper Duration: 2-3 weeks before race A | Goal: restore freshness without losing adaptations. Progressive volume reduction (-30% / -50% / -70% over 3 weeks), intensity maintained (2-3 short sharp sessions per week). Rest days active or passive depending on profile.

How many weeks per phase by target distance

The duration of each phase depends on the target distance and starting base fitness:

Golden rule: the base must never be sacrificed to reach build faster. Build gains are proportional to base quality. A rushed base = a build capped at 60% of potential.

For a first Ironman: plan at minimum 24-30 weeks from the start of the structured plan. If base fitness is solid (10h+ of sport per week habitually, 1-2 years of triathlon), 20 weeks may suffice with a compressed base phase.

Recovery weeks: insert 1 recovery week (volume -30-40%, no intensity) every 3-4 loading weeks. These weeks consolidate adaptations : removing recovery weeks = overtraining risk + regression.

Planning B-races and transition periods

B-races are secondary events slotted into the season to test fitness, practise logistics and stay motivated. Rules:

• Maximum 1 B-race every 3-4 weeks in build phase (otherwise they consume the recovery needed for adaptations)
• Treat a B-race as a quality session (no taper, normal recovery before and after)
• Never place a B-race in the 4 weeks before race A (residual fatigue)

Post-season transition (often neglected): After race A, don't immediately return to structured training. A 2-4 week transition period : sport only for pleasure, no programme, no zones : allows physical and mental recovery. Athletes who skip this period often burn out mid-next-season.

Planning the next season:

• Wait 3-4 weeks post-race A before committing to next season
• Make an honest assessment (weak points: swim? bike climbs? run hydration management?) and orient the next base phase toward identified gaps
• Choose the next race A 8-12 months in advance to size the plan correctly

Warning signal: reverse periodisation. If you arrive at race A fatigued, the problem is almost always in the build phase (too much threshold volume, recovery weeks too short, too many B-races). The solution isn't training more : it's training smarter.

Why the core is crucial across all three disciplines

Swimming: efficient freestyle propulsion comes from trunk rotation, not just the arms. Weak core = rotation compensated by shoulders → rotator cuff tendinitis risk + 5-10% swimming efficiency loss. Horizontal position (ventral bracing) also reduces drag : every degree of hip drop increases water resistance.

Bike: in aero position (elbows on aerobars), it's the core : deep abdominals (transverse), erectors, obliques : that keeps the back flat. Weak core = rounded back after 2-3 h → lower back pain, power lost to the pedal (-5 to -10 W in wind tunnel measurements), head-up position change (+ aerodynamic drag). On an Ironman bike of 5-7 h, postural endurance is non-negotiable.

Run: under post-bike marathon fatigue, core prevents excessive lateral oscillation and hip drop. Each centimetre of unnecessary lateral movement costs energy. Triathletes with a strong core preserve their running economy to km 35-40; others lose it from km 25.

Essential exercises for triathletes

Anti-rotation bracing and stability (3-4 sessions/week, 15-20 min):

Front plank

• Position: elbows under shoulders, body aligned heels-shoulders-occiput, neutral pelvis (neither anterior nor posterior tilt)
• Duration: 3 × 30-60 s with 30 s rest
• Classic mistake: posterior tilt (hips in the air) or anterior tilt (lower back arch) : avoid both

Side plank

• Position: elbow under shoulder, body straight foot to head, hip doesn't sag
• Duration: 3 × 20-40 s per side
• Progression: raise top leg / rotate top arm toward ceiling

Bird-dog

• Start on all fours, flat back (light abdominal brace), simultaneously extend right arm and left leg to horizontal, hold 2 s, return without putting them down
• 10-12 reps per side, 2-3 sets
• Key exercise: anti-extension strength + cross-coordination (mirrors the running gait)

Dead bug

• Lie on back, arms vertical above shoulders, hips at 90°, knees at 90° (table position)
• Simultaneously lower right arm and left leg toward floor without lower back lifting off
• 8-10 reps per side, 2-3 sets : lower back stays pressed to floor throughout

Thoracic rotation (swim-specific)

• Lie on side, knees bent, arms stacked in front. Rotate top arm backward opening the chest, keep hips still.
• 10 reps per side : trains the thoracic mobility needed for swim rotation

How to integrate core work into a triathlon training plan

Recommended frequency: 3-4 sessions per week of 15-20 minutes. Core sessions don't require long recovery : they can be done in the morning, before a cardio session, or directly after an easy session.

Timing in the week:

• Option A : post-swim session (recommended): 15 min of core right after swimming. The mild fatigue state activates stabilisers correctly.
• Option B : morning fasted (dedicated session): 20 min core + 5 min mobility. Ideal on recovery days.
• Option C : before indoor bike (Zwift): bird-dog + dead bug + front plank just before getting on the home trainer.

Avoid intense core before a key session: intense core work just before an interval run or bike hill session will fatigue stabilisers and undermine main performance. Keep core for after or on easy days.

Progression through the season:

• Base phase: static exercises (plank, side-plank, bird-dog) → build bracing endurance
• Build phase: dynamic exercises (dead bug, rotations, Pallof press) → functional strength
• Peak / taper phase: maintenance with 2 sessions/week, reduced volume : no new exercises before race A

Warning signal: if you feel lower back discomfort on the bike after 60-90 min (no injury, just postural discomfort), it's almost always a core deficit. 4 weeks of regular core work often fixes it.

The 5 major differences between pool and open water

1. No lane line, no visual reference: in the pool, your gaze follows the T on the bottom. In open water, you must lift your head (sighting) every 6-10 strokes : which costs energy and disrupts rhythm.

2. Wetsuit: the wetsuit forces hips higher and changes buoyancy. Swimmers used to flat pool lanes often find the position 'too high' and arm power modified. It must be tested in training before the race.

3. Opaque and cold water: without underwater visual references, balance sense is more challenged. Cold water (< 18°C) triggers a reflex hyperventilation on immersion : know this reaction before experiencing it in a race.

4. Mass start: starting with 200-2000 other swimmers creates turbulence, involuntary hits, a racing heart rate. The first 200-400 m of a mass start are among the most stressful moments in triathlon.

5. Navigation and current: without lane lines, you can drift 5-30 metres over 1000 m without realising if you don't master sighting. A lateral current amplifies the error.

Pool-specific drills to prepare for open water

Sighting drill (train the head lift):

• Swim normally, every 6 strokes lift your head forward (gaze horizontal at the water surface, not toward the sky) for 1-2 seconds, then resume natural rotation
• Goal: don't break arm rhythm or sink hips during sighting
• Recommended volume: integrate into 400-800 m of your sessions 2×/week

Swimming without bottom reference (eyes closed):

• Close eyes for 10-15 m in a straight line → assess your natural drift
• Reveals if you have a pull or rotation imbalance : most swimmers drift 0.5-2 m
• Correct via symmetric catch drills (paddles, unilateral water-catch drills)

Simulated mass start:

• With 4-6 swimmers in the same lane, all start simultaneously and hold lane for the first 50 m
• Habituates to congestion, turbulence, start stress without strategy
• Variant: start side-by-side (3 swimmers abreast in the wide lane), trains finding a draft

Pool swimming with wetsuit:

• 2-3 sessions with your actual wetsuit before the race : in a pool that allows wetsuits (check)
• Observe: does your position change? Does arm cadence adapt? Any neck irritation?
• First 'too high position' feeling = normal, adapts in 10-15 min

No lane-line sequences:

• Swim diagonally corner to corner in an empty lane while holding a bearing
• Forces use of proprioception and distant visual references rather than the bottom line

How to structure the pool → open water transition in your training

Planning your first open water sessions:

• First open water session: 15-20 min maximum, calm water (lake, protected body of water), with a partner or safety kayak
• Don't start directly in the sea or choppy water
• Session 1 goal: just test buoyancy (with or without wetsuit), sighting, and familiarise with the space

Recommended open water vs pool volume by season:

• Base phase (winter-spring): 90% pool, 10% open water (if accessible). Work on technique and lane volume.
• Build phase: 70% pool, 30% open water. Integrate 1 open water session/week, first 1200-1500 m then progressively to 2500-3000 m.
• Peak / taper phase: 50-60% open water if available. Replicate race conditions (distance, wetsuit, sighting).

The week before the race:

• If possible, do 1 session in the course water or similar water (salt vs fresh = 2-3% buoyancy difference)
• Test water entry with wetsuit
• Locate the buoys on the course map and practise memorising them

Managing cold water reaction:

• If water is < 16-18°C, immerse gradually (enter, splash face, dip head) for 2-3 min BEFORE the official start
• The reflex hyperventilation lasts 60-90 seconds : wait for it to pass before sprinting

Why altitude improves endurance

At altitudes > 2000 m, partial oxygen pressure is lower. The body responds by producing more erythropoietin (endogenous EPO), stimulating red blood cell production and increasing oxygen delivery to muscles.

After 3 weeks at 2200–2500 m, typical observations include:

• +3 to 8% haemoglobin
• +3 to 5% VO2max over time
• Improved running economy

These gains last 2–4 weeks after returning to sea level, which is why athletes time altitude camps 2–4 weeks before their target race.

The golden rule: 'live high, train low'

The scientifically validated protocol is 'live high, train low': sleep and recover at altitude (2000–2500 m), but train at lower altitude (< 1500 m) to maintain intensity.

Why? At high altitude, maximum power drops by 5–10% (less O2 available). Too-intense training at altitude = degraded sessions, extended recovery, and sometimes overtraining.

Moderate altitude (1200–1600 m): weaker adaptations but training maintained. A valid compromise for amateurs.

Low altitude (< 1000 m, e.g. Spanish Pyrenees): near-zero haematological benefits, but the change of environment, volume of cycling/running on flat or rolling roads, and the weather can justify a camp for other reasons.

Acclimatisation: the first 3 days

The classic altitude camp mistake: arriving Sunday evening and doing a big session Monday morning.

The first 48–72 hours: the body tries to compensate for lower O2 by increasing heart rate (+10–20 bpm at rest) and breathing. Common symptoms: headache, fatigue, mild nausea, disrupted sleep. This isn't the flu : it's acclimatisation.

Recommended protocol:

• Day 1–2: easy conversational-pace outing (< 70% max HR), duration reduced by 20–30%
• Day 3–4: gradually return to usual volumes
• From day 5–7: add moderate intensity blocks

Never ignore a persistent headache combined with confusion, ataxia (loss of balance), or breathlessness at rest: these are signs of severe acute mountain sickness (AMS). Descend immediately.

Drafting physics in swimming and the wake zones

A swimmer creates two exploitable wake zones:

Zone 1 : Direct wake (0-50 cm from the feet): drag reduction of 18-26% (Bassett et al., 1991; confirmed Chatard & Wilson, 2003). The lead swimmer moves the water : you benefit from this flow. This is the optimal position but hard to hold: if you regularly touch their feet, you annoy them AND lose your propulsion.

Zone 2 : Hip side (beside the swimmer, hip-to-shoulder level): 11-15% drag reduction. Less efficient but easier to sustain over long distance (lower collision risk, easier sighting).

Zone 3 : Out of wake: zero benefit. Swimming 2-3 m back = swimming alone.

Optimal strategy: Zone 1 on long straight sections, Zone 2 at buoy turns (less contact, better buoy visibility).

Finding and holding a draft in race

Finding a draft at the start: the first 200 m are chaotic. Let the fast wave go, then spot a swimmer slightly faster than you (or at your speed) swimming straight. Lock onto Zone 1, adapting arm cadence.

Holding Zone 1 without collision: stay 30-50 cm from the feet. Light touches = normal. Pro tips: watch the bubbles and foot movement, not the buoy (the lead swimmer sights for you). Slightly increase arm tempo (without extending length) to hold position without riding up on the feet.

Changing draft: if the lead swimmer slows, zigzags or goes off course → exit to the side, sight, find another group or position beside an adjacent group. Don't stay in a bad draft out of fear of losing shelter.

The swim pack: if a group of 5-10 same-pace swimmers forms, middle or side placement is often more efficient than behind the leader : less pressure, more rhythm stability.

Training volume, nutrition and pace management

Training volume: a serious 70.3 plan runs around 8-12 h/week in build phase. A Full Ironman plan reaches 12-18 h/week. It's not just more sessions : it's their individual length. In 70.3, the max long bike is 3h-3h30. In Ironman, it rises to 5h-6h. Recovery between long sessions is slower; 3+1 cycles often become essential.

Race nutrition: in a 70.3 (4-7 h race), you can almost get by with a rough strategy. In an Ironman (9-14 h), poor nutrition destroys the race. For the first 8-10 hours, the athlete must absorb 60-90 g of carbs per hour : in all conditions (heat, stress, aero bike position). GI problems are the leading cause of DNF in Ironman. Race nutrition must be rehearsed in training, not improvised on race day.

Pace management: in a 70.3, a slight pacing error on the bike costs 10-20 min on the half marathon. In an Ironman, the same error can make the marathon impossible to run (walking). The rule: Ironman bike pacing = 70–77% of FTP maximum. Any deviation above 80% for more than 5 consecutive km = danger.

The 3 crisis points you don't see in 70.3

Every 70.3 triathlete who has completed their plan and run their race believes they know the hard spots. The Full Ironman adds three that shorter distances don't reveal:

Bike km 100–120 crisis (h+5 to h+6): glycogen stores are starting to deplete, saddle soreness appears, the mind begins to question the decision to enter. This is the 'bike wall'. Solution: refuel early (from h+1, not when hungry), maintain high pedalling cadence (90+ RPM to spare the quadriceps).

Marathon km 10–15 crisis (h+9 to h+10): legs that have held a jogging pace until now begin to solidify. This is often where triathletes who haven't drunk enough enter dehydration or cramp crisis. Solution: hydrate at every aid station, take sodium, and accept reducing pace by 10-15 s/km if needed rather than 'holding on' and blowing up 3 km later.

Marathon km 30–35 crisis (h+11 to h+12): the 'zone of all pain'. This is where pure willpower takes over from physiology. Strategies that work: break km down one by one (not '7 km left', but 'next aid station in 800 m'), change goal (not the time, just finish), walk the hills to preserve the rest.

The 4 concrete benefits for a triathlete

1. Swim symmetry: breathing only to the right (or left) creates structural asymmetry : the pull is stronger on the breathing side, creating progressive course drift. In open water, without a black line, unilateral breathers often swim 5–15% further than the straight-line distance. Bilateral breathing forces a symmetrical pull.

2. Open water vision: breathing on both sides lets you see both sides of the pack. You can adjust your positioning in the mass, avoid getting hit/hitting others, and watch buoys in both directions without changing your technique.

3. Prevention of neck pain: always rotating to the same side creates asymmetrical loading on neck and shoulder muscles. Triathletes who only breathe to the right often develop chronic cervical tension on the breathing side. Alternating relieves this tension.

4. Adaptability to conditions: if the sun is in your eyes to the right, waves come from the left, or the pack pushes from one side : the bilateral swimmer adapts. The unilateral swimmer swallows waves or closes their eyes depending on the situation.

How to learn: 3-week progression

Most swimmers try to switch to bilateral too fast, forcing it every length. Discomfort creates anxiety and they give up after 2–3 sessions. The right progression:

Week 1 : Awareness: swim 5 × 100 m breathing every 2 strokes (fast unilateral), then alternate with 5 × 100 m breathing every 3 strokes (bilateral). The goal isn't perfection : it's feeling the differences. Note: breathing every 3 strokes = slightly less oxygen initially, this is normal. The body adapts.

Week 2 : Bilateral blocks: during each session, dedicate 30% of the volume to bilateral breathing (every 3). Use easy lengths (60–70% effort) for bilateral blocks. Technique alone is enough load.

Week 3+ : Structured mix: 2 bilateral lengths (every 3) then 1 unilateral right length. Progressively increase the bilateral proportion. Within 6 weeks, most swimmers reach functional bilateral breathing on 80% of their distance.

Key drill : '3-3-3': breathe 3 times to the right, 3 times to the left, 3 times bilateral (alternating). This drill forces the brain to switch regularly and develops rotational muscular symmetry.

Bilateral in racing vs bilateral in training

A commonly misunderstood point: the goal of bilateral breathing is not to do it 100% in racing.

In racing (maximum effort, choppy water, mass start):

• Breathing every 2 strokes (fast unilateral) is often needed to maintain intensity, especially early in the race when heart rate is high
• Bilateral (every 3) is ideal for long, steady phases where intensity is controlled
• Alternate: 6 bilateral strokes + 4 fast unilateral strokes based on intensity and conditions

In training:

• Bilateral is the default (symmetry development)
• Unilateral is reserved for pure speed sessions or active recovery

The athlete who masters both modes can choose based on the situation : that's the real strategic advantage of bilateral: not forcing yourself to breathe less, but not being constrained by direction.

What is a brick workout?

A brick = a bike session immediately followed by a run, with no break. The goal is to simulate real T2 conditions (bike-to-run transition) and train the neuromuscular system to switch posture, muscle recruitment, and sensation.

The first minutes of running after cycling are often uncomfortable (heavy legs, choppy stride) even for well-trained athletes in each discipline separately. That's exactly what the brick targets.

Why it works: the mechanism

Cycling mainly loads the quadriceps in a closed seated position (hip flexion). Running upright engages hamstrings, glutes, and calves more in an extension chain. This abrupt switch temporarily disrupts the motor pattern.

With repetition, the nervous system learns to switch faster between the two modes. The 'heavy legs' sensation fades after 1–2 km instead of 5–6 km for an athlete not trained in this sequence.

Recommended protocols by phase

Base phase: short adaptation brick : 45 min endurance bike + 15 min easy run. Frequency: every 2 weeks. Goal = build the transition reflex, not load.

Build phase: progressive brick : 1h30 bike with tempo portion (Z3) + 20-30 min run with last 10 min at target 70.3 or Ironman pace. Frequency: once a week.

Peak phase: race-day simulation brick : 2h bike (Ironman race-pace Z2/Z3) + 30-40 min run at target Ironman pace. Every 2 weeks, with enhanced recovery.

Common mistake: bricks that are too long and too intense in the base phase. Over-stimulation without prior adaptation increases injury risk without additional benefit.

Simulated T2: optimizing the transition

T2 is run : literally. Goal: dismount, rack the bike, put on running shoes, go. In competition, every 10 seconds lost in T2 is an avoidable mistake.

In training, include quick mini-transitions 1-2 times per month: rack the bike, put on running shoes, start within 60-90 seconds. Doing this quickly is a skill : and it's better to learn it in training than on race day.

Principle: reduce volume, maintain intensity

The classic taper mistake = cutting everything. Volume AND intensity. Result: the body arrives at the race low-fatigue but also under-stimulated : legs lack reactivity.

The scientifically validated model (Banister, Mujika): reduce volume 40-60% over 2-3 weeks, but maintain intensity (a few short race-pace reps). Muscle fibers stay stimulated, glycogen stores rebuild, accumulated fatigue drops.

Duration by event type

Sprint / Olympic: 1 week of reduction is enough. Load is moderate, recovery is fast.

70.3 (Half Ironman): 10-14 days. Last long session at D-14 to D-10. Week D-7: volume -50%, some race-pace blocks (10-15 min).

Full Ironman: 2-3 weeks, even 3 full weeks for high-volume athletes (>12h/week). Last long bike ride D-21. Last long run D-14. Last big swim week D-14.

Race week: what to do?

D-7 to D-3: short sessions (30-45 min) in endurance, no physical stress. Swimming 2-3 times (maintain water feel). Bike 1-2 times, run 1-2 times, all low intensity.

D-2: short activation : 20 min bike with 3×1 min at race pace, 10 min easy run. The goal is neuromuscular: activate the system, not fatigue it.

D-1: active rest or easy 20 min swim. Equipment prep, logistics, sleep. No intense 'recovery session': a pre-race-A injury happens.

Taper free time ≠ dead time. It's when the mind settles. Read your plan, visualize transitions, prepare nutrition.

Taper blues: normal, not a crisis

Almost all athletes feel taper blues: heavy legs, doubts, imagined aches. It's a known physiological effect : the volume drop reduces endorphins, soreness from the loading phase surfaces.

Sign things are fine: you feel heavy from D-14 to D-7, but light and reactive from D-5 to D-1. If it's reversed (light at D-14, heavy at D-1), the taper was too short or too light.

Where does 180 spm come from?

Jack Daniels (elite running coach, 1970s-80s) observed that Olympic runners ran at around 180 steps per minute or more, regardless of distance. The rule became a benchmark in running.

What research actually says: a high cadence (180±10 spm depending on build and pace) is associated with shorter stride, reduced ground contact time, and less load on the knee and tibia : reducing injury risk. It's not magic: it's mechanical.

In triathlon: context changes everything

After cycling, the neuromuscular system is pre-fatigued in a different muscle recruitment mode. The stride tends to lengthen and become heavier : heel striking harder, center of gravity dropping.

A slightly higher cadence than usual helps short-circuit this pattern: increasing steps/min mechanically forces the stride to stay short and light, reducing impact and preserving energy.

For Ironman athletes: targeting 170-180 spm in the early marathon (first 10-15 km) is reasonable. Beyond that, pace management takes priority over form.

How to increase cadence without injury

Don't jump from 162 to 180 spm overnight. Muscular load (calves, Achilles tendons, plantar fascia) increases with high cadence : the transition must be gradual.

Gentle increase protocol: identify your base cadence (measure over 1 min of easy running). If below 168 spm: add 2-3 spm every 2-3 weeks. Use a running metronome (app or GPS watch) to target a precise cadence for 5-10 min blocks.

Focus on sensation, not the number: the useful image is 'running like the ground is hot' : short, light, reactive. This frames correct form without mental calculation.

What happens physiologically in the heat

When ambient temperature exceeds 20-22°C, the body must manage two simultaneous demands: perfuse working muscles AND dissipate heat via sweating and skin vasodilation. Both processes compete for the same cardiac output.

Consequence: for the same power or pace, HR rises 10-20 bpm in heat vs cool conditions. The lactate threshold (FTP on bike, threshold pace in running) drops 5-10% below the 'thermoneutral' threshold (approximately 15-18°C).

In practice, riding at your usual FTP watts at 32°C is equivalent to riding above threshold in temperate conditions. Power management must be adapted, not ignored.

Heat acclimatization: practical protocols

Physiological heat acclimatization builds over 8-14 days of regular exposure. Measured adaptations: plasma volume increases (better muscle hydration), earlier sweat onset, reduced lactate at a given intensity, stabilized HR.

Available acclimatization methods:

Training in natural heat: perform long sessions between 11am and 3pm if local conditions allow (3-4 sessions/week, 20-90 min). Full adaptation in 10-14 days.

Post-exercise sauna (passive heat acclimation): 20-30 min sauna (80-85°C) after a normal session, 4-5 times per week for 10-14 days. Comparable effectiveness to heat training, more accessible in northern Europe.

Hot bath post-exercise: 40 min in a bath at 40°C. Alternative to sauna, same frequency. Protocol validated by several studies on elite runners (Périard, 2015).

Race strategies in heat

Precooling: wearing an ice vest 20-30 min before the start. Lowers the starting core temperature, pushing back the overheating threshold. Effective when available : otherwise: cold water on neck and wrists, cold concentrated drink 30 min before.

Adjust power/pace targets: at 30-35°C, reduce target watts by 5-10% on the bike. Running by HR (rather than GPS pace) protects better in heat : HR tells you what the body is actually experiencing.

Hydration and electrolytes: sodium needs double in intense heat (2-4 g/h possible for a high-sweat athlete). Don't rely solely on thirst : thirst sensors are imprecise during racing. Clear-golden urine = good hydration; dark yellow = deficit.

Active cooling during the race: cold water sponges on neck, head, armpits at every aid station. Delaying core heat effects by 10-15 min per cooling station passage.

What the warm-up triggers physiologically

The warm-up serves three simultaneous functions:

Increasing muscle temperature: the speed of fiber contraction and relaxation increases with temperature. A muscle at 38-39°C produces force up to 20% faster than at 36°C. This directly translates into better movement economy and less perceived effort at the same pace.

Progressive cardiorespiratory activation: jumping abruptly from a resting HR (50-60 bpm) to a threshold HR (160-175 bpm) without transition creates an initial O₂ debt. The body compensates via anaerobic lactate metabolism, prematurely acidifying the muscles and reducing the duration of the target effort.

Neuromuscular pre-activation: the first repetitions of a movement (stride, pedaling stroke, pull) are less efficient than subsequent ones. The nervous system needs a few minutes to synchronize motor unit recruitment. That's why athletes do accelerations or strides before a threshold session : not just to 'finish warming up' in the colloquial sense.

Protocols by discipline

Swimming: 400-600 m progressively. First 200 m at zone 1 (technique, body awareness), 200 m at zone 2, then 4 × 25 m progressive accelerations (buildups) with 15 s recovery. Total: 10-12 min. Don't skip the buildups before a threshold set or sprints : they're what activates fast-twitch fiber recruitment.

Cycling: 15-20 min at zone 1-2, ideally on a trainer (controlled) before an outdoor session. Include 3-4 accelerations of 20 s (high cadence, 90+ RPM, zone 3-4) in the last 5 minutes of warm-up. These 'openers' open the fast neuromuscular pathways without creating muscular fatigue. On an FTP test or a threshold-pace ride, never start the effort without these openers.

Running: 10-15 min of easy jogging (zone 1-2) + 4-6 strides (80-100 m accelerations at 5K pace, walking recovery between each). The strides are the key: they activate fast-twitch fibers, improve tendon elasticity, and allow you to hit target pace from the first km of the main set rather than the third.

Warming up before a race

Ironman or 70.3 logistics constrain the warm-up: no free swim lane before a mass start, little room to do strides. But margins remain.

Water entry zone: if open (rolling start, time-based wave), enter the water 8-10 min before the gun. Do 200-300 m progressively, a few 25 m accelerations. This allows reaching the aerobic crossover before the clock starts : and avoids the cardiac and thermal shock of the first dozens of meters.

If the water entry zone is closed: 10-15 min easy jogging + 4-6 strides before entering the start chute. Warm muscles stay primed for 15-20 min in the water : more than enough to wait in the chute and handle the first minutes.

On the bike: the first 20-30 km functionally serve as a warm-up. Don't start at target pace immediately (especially after a 50-90 min swim that's already taxed the upper body) : treat the first 20 km as a progressive power build.

What is cardiac drift and Pa:Hr decoupling?

During a long effort at stable pace (zone 2, 65-75% HRmax), the heart must maintain cardiac output by increasing frequency to compensate for cardiovascular drift (CV drift). Main causes:

• Dehydration: blood viscosity increases, stroke volume decreases, the heart compensates by speeding up.
• Thermal redistribution: the longer the effort, the more blood is redirected to the skin to dissipate heat, reducing venous return.
• Muscular fatigue: less efficient muscles demand more O₂ to maintain the same pace.

Pa:Hr decoupling (Pace:Heartrate) is the drift ratio between the first and second half of a long run. Formula:

Pa:Hr = (Pace_2ndHalf / HR_2ndHalf) / (Pace_1stHalf / HR_1stHalf) - 1

On Garmin Connect and Strava, this figure is sometimes calculated automatically and expressed as %. A decoupling < 5% on a 20-30 km long run (at zone 2, no extreme heat) indicates a good aerobic base.

How to measure decoupling on a long run

Conditions for a valid measurement:

• Minimum 20 km run (ideally 25-35 km)
• Stable zone 2 pace (HR ~65-75% HRmax) : no major elevation, no accelerations
• Normal hydration (not a voluntary dehydration test)
• No extreme heat (>25°C mechanically increases decoupling)

Manual calculation (if your device doesn't do it):

1. Split your run into two temporal halves (not distance-based)
2. Note the average HR and average pace for each half
3. Calculate the pace/HR ratio for each half (example: 5:30/km with HR 142 = 5.5 min·bpm⁻¹)
4. Decoupling = (ratio_2nd - ratio_1st) / ratio_1st × 100

On Garmin: the metric is called 'Aerobic decoupling' or 'Pa:Hr' in the activity analysis (visible in the Performance tab).

On Strava: decoupling is not natively calculated. Use a .fit export to Garmin Connect or TrainingPeaks to obtain it.

Interpreting results and acting

< 5% decoupling: good aerobic base. Current volume and intensity are well assimilated. You can consider a load progression (volume or intensity, not both together).

5-8% decoupling: moderate decoupling. Normal at the start of a phase, in heat, or after a high-load week. Monitor the trend over 4-6 weeks: if decreasing → adaptation. If stagnating or increasing → check load/recovery ratio.

> 10% decoupling: high decoupling. Multiple possible causes: insufficient aerobic base for target volume, chronic overload (accumulated fatigue), dehydration, heat, or ongoing illness. Don't panic over a single measurement : the 6-8 week trend is more informative than one number.

Trap to avoid: comparing runs in different conditions (winter vs summer, flat vs elevation, hydrated vs thirsty). Decoupling is a personal trend tool, not an absolute ranking.

The all-or-nothing temptation (and why it's wrong)

The common reasoning: 'I'm at the hotel, no pool, no bike : might as well do nothing.' This reasoning costs dearly in guilt and doesn't reflect physiological reality.

What you actually lose in 3-5 days without training:

• Aerobic base volume: negligible loss (aerobic adaptation is maintained for weeks without intense stimulus)
• Muscular strength: minimal loss over 3-5 days
• Motor coordination (swimming, cycling): slight over 1 week

What you potentially gain:

• Central recovery (nervous system) if the preceding period was heavy
• Compensatory sleep if the hotel is decent
• Renewed motivation upon return

Conclusion: 3-5 days without training don't destroy a base built over 6-12 months. The stress of guilt is often more costly than the break itself.

Strategies by context

Hotel with gym:

• Treadmill: short, quality sessions. 30-40 min at zones 1-2 or 20-25 min of short intervals (8 × 1 min / 1 min). No need to replicate the long run.
• Stationary bike: 45-60 min zone 2 or short sweet spot (15 min Z4). Treadmill > stationary bike for maintaining running coordination.
• Strength training: full reinforcement session (core, squats, lunges, push-ups) if no strength session in the preceding week.

Hotel without gym:

• Outdoor running: 30-45 min of neighborhood jogging. The unfamiliar environment is part of the challenge.
• Bodyweight session in the room: 3 × (10 squats + 10 lunges + 10 push-ups + 30 s plank) repeated 4 times, no equipment, 20 min.
• Local public pool: search for the nearest pool (Google Maps, 'swimming pool near me'). Even 1,000 m maintains coordination.

Long trips (>7 days):

• Treat the first 3-4 days as a micro recovery break.
• Resume progressively from day 4-5: one short session per day, no key sessions.
• Don't try to 'make up' missed volume on return : resume at 70% of habitual volume.

Planning proactively to reduce stress

Before the trip:

• Check whether the hotel has a gym or pool (something to actively book, not just hope for).
• Pack: running shoes (small), light elastic resistance band, swim kit (cap + goggles = 200 g).
• Identify 1-2 priority sessions to maintain during the period (e.g., the Sunday long run if you leave Friday night, or Tuesday swim if it's a loaded week).

During the trip:

• Use free time (mornings, evenings) for short sessions : even 20-30 min. Hotel mornings are often the most available before meetings.
• Sleep: if the choice is between a session and an extra hour of sleep after a night flight, take the sleep.

On return:

• No overcompensation. Resume the planned schedule, without doubling sessions to 'catch up'. Consistency over 4-8 weeks always beats one-off overload.

Why the first minutes after cycling are hard

Several physiological mechanisms explain the sensation of the first minutes of run-off-bike.

Blood redistribution: during cycling, blood flow is massively directed toward the quadriceps and glutes (dominant muscles). The transition to running demands stronger recruitment of hamstrings, calves, and ankle stabilizers : muscle groups that were less active. Local vascular redistribution takes 2-4 min to fully adjust.

Motor pattern change: pedaling (cyclical movement, continuous push) and running (elastic movement, flight phase) use different neuromuscular patterns. The brain must 'switch' patterns : hence the first clumsy strides and the feeling of shuffling.

Quadriceps fatigue: quads work hard during the push phase of pedaling. In running, they handle shock absorption eccentrically. Prior quadriceps fatigue reduces this absorption capacity, increasing stress on the knees and perceived stiffness.

HR reading lag: heart rate spikes in the first minutes of post-bike running. Inexperienced athletes panic and slow down, when it's actually a normal transition : HR stabilizes after 3-5 min at constant pace.

Specific adaptation through bricks

The only way to reduce the duration and intensity of the neuromuscular transition is to train it directly. Bike-run bricks are the tool.

Recommended frequency:

• In base phase: 1 short brick/week is enough (30 min cycling + 15 min run, at zones 1-2). The goal is to create the neuromuscular connection, not generate fatigue.
• In build phase: 1-2 bricks/week, including 1 with a longer run (20-30 min) or at pace close to race target.
• In peak phase (3-6 weeks before race): 1-2 bricks/week with 30-45 min runs, including 10-15 min at IM run target pace.

Key to adaptation: the criterion is not the total volume of the brick but the repetition of the cycling→running switch. 10 bricks with 20 min runs are more adapting for the transition than 3 bricks with 60 min runs.

What to feel as progress:

• The duration during which legs feel 'heavy' decreases (from 8-10 min to 2-4 min after 6-8 weeks of specific training)
• Stride stabilizes faster
• Post-transition HR spike becomes less surprising

Pace management in the first minutes of the run during a race

The most common trap in competition: getting swept up by adrenaline and starting the first 2-3 km of the run too fast, when legs aren't yet 'clean.' The result: early muscular debt that shows up at km 15-20 as pace degradation.

Recommended strategy:

• Km 1-2: 10-15 s/km slower than target pace. Let the switch happen. HR is climbing : that's normal.
• Km 3-5: adjust toward target pace if legs feel clean. If still heavy, wait.
• Km 5+: commit to target pace or slightly below depending on heat and perceived fatigue.

T2 exit technique: maintain high step cadence (>165 spm) immediately upon leaving the bike : even if speed is low. This activates the running neuromuscular pattern faster than long slow strides. Counting steps over 15 s (>41 = >164 spm) is a quick roadside check.

Protocol: 400 m then 200 m all-out

The standard protocol uses two all-out efforts with 10 min recovery between them:

Warm-up: 400-600 m at easy pace + 2x50 m building.

Effort 1: 400 m all-out. Aim for your best possible time. No sprint start: manage your effort to hold pace all the way. Note your time in seconds.

Recovery: 10 min easy swimming or full rest.

Effort 2: 200 m all-out. Same logic: race management, best possible time. Note your time in seconds.

Cool-down: 300-400 m at easy pace.

The test is invalid if you blow up on the 400 m or if the 200 m is done at less than 80% of the theoretical maximum time. If so, repeat after 48 h of rest.

Calculating your CSS and using it in sessions

The CSS formula is straightforward:

CSS (sec/100 m) = (400 m distance - 200 m distance) / (400 m time - 200 m time) x 100

Example: 400 m in 6 min 20 s (380 s), 200 m in 2 min 55 s (175 s). CSS = (400 - 200) / (380 - 175) x 100 = 200 / 205 x 100 = 97.6 s/100 m = 1 min 37 s/100 m.

Use in sessions:

• Threshold intervals (6-10 x 100 m, 10-15 s rest): hit your exact CSS pace.
• Long intervals (3-5 x 400 m, 30-45 s rest): CSS +2 to +5 s/100 m (slightly slower).
• Active recovery: CSS +20 s/100 m minimum.

CSS replaces HR zones in swimming (they are unreliable in cold water and with head submerged). It gives you a precise, repeatable speed reference from one pool to the next.

When to retest and how to progress

Retest frequency: every 6-8 weeks in build phase, or after a 2-week rest period (swimming detraining is rapid). CSS can drop by 3-5 s/100 m in just 2 weeks without swimming.

Signs of progress: your CSS pace drops (= you go faster), old-CSS interval sessions feel submaximal, you hold 6 x 100 m at less perceived effort.

Typical 12-week progression:

• Weeks 1-4: protocol familiarisation, 2-3 sessions/week including 1 at CSS.
• Weeks 5-8: long series (3 x 400 m at CSS+3 s), 3.5-4.5 km/session volume.
• Weeks 9-12: short fast intervals (12 x 50 m at CSS-2 s, 10 s rest) + 1 long at CSS pace.
• Retest in week 12 before taper.

Note: the protocol is demanding. Doing it after a tiring session distorts results. Always freshly rested or after a light warm-up only.

A 10 h build-phase sample week

Here is a sample build week for an amateur triathlete with 10 h volume, 2 key sessions and a long weekend:

Monday: rest or 30 min technique swim (active recovery after the weekend).

Tuesday: bike threshold 75 min (2 x 20 min at FTP, 5 min recovery). Key session #1. Evening: 45 min endurance swim (optional if double is not tiring).

Wednesday: run endurance Z2 60 min. Moderate volume, conversational pace.

Thursday: swim intervals 50 min (6-8 x 100 m at CSS, 15 s rest). Main swim session. Optional: 30-45 min Z2 bike (easy, to maintain pedalling feel).

Friday: rest or 20 min mobility. If load is high, full rest.

Saturday: long bike ride 3 h (Z2 with 30 min Z3 in the middle). Main bike volume of the week.

Sunday: long run 1 h 30 to 1 h 45 (Z2, Ironman pace or slightly below). Key session #2 of the weekend.

Week total: 10 h, 8 sessions, 3 balanced disciplines.

Real trade-offs when time is short

What to cut first (in order of sacrifice):

1. The optional second sessions on Tuesday and Thursday. This takes you from 8 to 6 sessions, from 10 h to ~8 h.
2. Friday rest stays as rest (do not fill it because the week got lighter).
3. Monday swim becomes a recovery priority: shorten to 20 min or drop it based on felt fatigue.
4. If only one weekend session is possible: prioritise the long bike (most Ironman-specific, hardest to replace). The long run can be reduced to 60 min Z2.
5. Never sacrifice the 2 key sessions (Tuesday bike threshold + Sunday long run) in a normal week. They are the heart of adaptation.

When to double up:

• Swim + bike: OK (non-competing muscle groups).
• Bike + run: OK only if the bike stays in Z2 (otherwise brick = key session in itself, do not add on top).
• Run + run: avoid unless you have a strong marathon background.

Adapting to your main constraint

If you start work early (7 am departure): morning sessions move to 5:30 am. Swimming and running are feasible early, as is home-trainer cycling. Avoid the key bike threshold session in a tired morning state (risk of underperforming and miscalibrating). Saturday's long bike ride is then your only high-volume window: protect it absolutely.

If you have little weekday time (< 5 h Mon-Fri): focus on one key weekday session (bike threshold or run threshold) and load the weekend (3-4 h bike Saturday + 2 h run Sunday). This pattern gives ~8-9 h with 5-6 sessions, sufficient for Ironman preparation.

If swimming is your weakness: increase to 3 swim sessions (Monday technique + Thursday intervals + Saturday morning before the long bike). Slightly reduce weekday run volume. An athlete who swims 30 min too slowly reaches the bike with a 10-min deficit and 30% extra muscle fatigue.

If you come from running: protect the weekday swim at all costs, even if running suffers. Swim threshold (CSS) and open-water volume are the fastest progress variables in build phase for a converted runner.

Chronotype: early bird vs night owl

Chronotype is your natural circadian rhythm - it is largely genetic and remains stable in adulthood. Early birds (around 25% of the population) reach their physical performance peak between 10 am and 2 pm. Night owls (25%) peak between 4 pm and 8 pm. The majority (50%) is intermediate, peaking around 2-6 pm.

Knowing your chronotype is not a luxury: studies show athletes training outside their optimal window produce on average 6-8% less power output, and their threshold HR is higher at the same effort. On a 70.3, that translates to 8-12 extra minutes.

Intensity and time of day: synchronise your key sessions

Sessions most sensitive to chronotype: threshold and VO2max intervals (effort >90% HRmax), long run at race pace, FTP test. These show the largest performance gap between circadian peak and trough (8-12%).

Less sensitive sessions: base endurance zone 2 (HR 60-70% max), technique swimming in calm water, compensatory strength training. The gap drops to 2-3% - negligible.

Practical rule: if you have the choice, schedule your most important key session of the week (FTP test, race-pace long run, 30/30 intervals) in your peak window. All other sessions fill volume without time-of-day constraints.

In practice: adjusting your schedule to your chronotype

You are an early bird (6 am = already in shape): key sessions can be done early without loss. Avoid late-evening competitions (if you have the choice) as your peak will be reduced.

You are a night owl (tough before 9 am): do not force yourself to do your FTP session at 5:30 am. If that is the only slot, drop intensity by 5%: a solid endurance session beats a failed interval that skews your zones. Reserve morning slots for technique sessions (swimming) or light volume.

Work constraint (only slot = 6 am): accept that your tests and key sessions will be systematically below your real potential. Calibrate your zones 5% higher if you only test FTP in the morning and are clearly a night owl. In competition, if possible, choose races timed around your peak.

What changes after 40

VO2max declines by about 1% per year after 30 without training; but with structured training, the decline drops to 0.3-0.5%/year, often imperceptible over 5 years. So VO2max is not the real problem.

What actually changes: recovery time between two key sessions lengthens (+20-50% in studies), muscle micro-damage after a long run or intensive block takes longer to resolve, and anabolic hormone levels (testosterone, GH) are lower at rest. Result: absorbing two threshold sessions within 48 hours becomes riskier after 40.

The 1.5 x rule: multiply recovery time by 1.5

Simple rule to apply: if at 25 you fully recovered from a key session in 36 hours, think 48-54 hours after 40. In practice:

• Bike threshold session (1 h at FTP): 48 h minimum before the next key session
• Long run > 25 km: 3 days recovery before another long effort
• Three-day loaded block: one reduced week (60-70% load) is needed after, not two days

Direct consequence: reduce key sessions per week from 3 to 2 if you are over 40 and do not yet have 10+ years of training history. Replace the 3rd key session with a pure zone 2 endurance session.

Volume vs intensity: the right masters balance

Counter-intuitively, masters athletes should not reduce intensity but the volume of intensity. Doing 10 x 1 min @ 110% FTP intervals is as beneficial after 40; doing it twice a week is too much.

Recommended pattern (beginner-intermediate masters):

• 80% of time in zone 2 (like everyone)
• Maximum 2 key sessions per week (threshold or VO2max), never on consecutive days
• Build block: 3 loaded weeks + 1 reduced week (not 4+1 as for younger athletes)

What works very well after 40: compensatory strength training 2x/week (plyometrics, eccentric hamstring strengthening) significantly reduces injury risk and offsets the slowdown in muscle protein synthesis. Do not skip it.

Why exhale underwater?

In crawl, the breathing window (head rotated) lasts about 0.4 to 0.6 seconds. If you only exhale during this window, you must simultaneously empty and fill your lungs - impossible to do correctly. Result: incomplete inhalation (70% capacity), CO2 retention, and HR climbing unnecessarily.

Solution: exhale progressively UNDERWATER during the 1.5 to 2 arm cycles that precede the breath. When you rotate your head, lungs are nearly empty: you only need to inhale in 0.4 s, which is perfectly feasible.

Trained swimmers do this naturally. Triathletes who came from running or cycling have almost systematically this technical deficit because they learned alone or late.

Continuous vs explosive exhalation

Two valid techniques to choose from based on your level:

Continuous exhalation (recommended for beginners/intermediates): release a steady trickle of air through nose and/or mouth throughout the underwater phase. Constant, regular bubbles. Advantage: maintains pressure in nasal passages, avoids swallowing water. Disadvantage: requires conscious regulation at first.

Explosive exhalation (advanced athletes): hold air during the first half of the cycle, then exhale rapidly (burst) the last fraction of a second before rotating the head. Advantage: easier to learn, closer to natural reflex. Disadvantage: leaves more CO2 in circulation if poorly dosed.

For most amateur triathletes: start with continuous exhalation, it corrects the root problem more completely.

Progressive drills: 3 weeks to ingrain the movement

Week 1: static face-in-water. Pool edge, face in water, exhale slowly through nose for 10 s. Repeat 5 times. Goal: get comfortable with nasal underwater exhalation without swimming constraints.

Week 2: kickboard drill. Board at arm's length, leg kick crawl, face in water, exhale continuously. Every 6 kicks, rotate head to inhale (inhale only). 4 x 25 m per session.

Week 3: full swim with HR check. Swim 100 m at moderate pace applying continuous exhalation. Note your HR at mid-length (if you have a waterproof watch). Compare with a swim without exhalation instruction. The 8-12 bpm gap is perceptible from the first attempt if you had the old reflex.

In competition: the advantage is felt most on long distance (3.8 km Ironman). CO2 accumulation over 70 min of swimming without correct exhalation can raise exit-swim HR by 15 bpm - and impair the 180 km bike that follows.

Descending position: TT tuck

On a descent >4% without tight corners, adopt the tuck (also called TT tuck):

• Elbows on aerobars (or TT handlebar), forearms parallel
• Flat or slightly hollow back: aim for a 45-degree torso/thigh angle
• Head low aligned with body, gaze forward at 50-80 m
• Hips towards the back of the saddle: transfers weight to rear wheel, better stability
• Pedals at 9 o'clock / 3 o'clock (horizontal): protects if obstacle, lateral balance

What you gain: at 60 km/h descent, aerodynamic drag is 90% of total resistance. A clean tuck is worth 5-8 km/h with no extra muscular effort.

Braking and cornering: the technique that saves time

Brake BEFORE the corner, never inside it. Braking in a corner = locked wheels + crash. Protocol:

1. Sit up 50 m before the corner (exit the tuck)
2. Brake progressively (70% front brake, 30% rear)
3. Release brakes at corner entry
4. Lean bike + body inward (inside knee towards ground)
5. Resume pedaling at corner exit

Braking distribution: front brake = braking power (physics), rear brake = stability. On wet roads, swap to 50/50 to avoid front wheel lockup.

Classic mistake: braking too early = carrying too much residual speed into the corner. Brake hard and late, release early.

Recovering and fuelling on the descent

Long descents (>90 s) are the best nutrition windows in a race:

• Drink: no muscular effort = full gulp without choking risk. Aim for 200-300 ml per long descent
• Eat (gel, bar): hands available, no complex coordination
• Unload your legs: soft rotations (cadence 60-70 rpm, easy gear) to clear residual lactate before the next climb

Power strategy: if the descent is followed by a climb, do not pedal-brake at the end (use inertia to attack the bottom of the climb without surging). Saves 5-8 W average over the segment.

In an Ironman, a bike segment with 1500 m of elevation and well-managed descents can represent 4-7 min gained vs a cyclist who brakes everywhere.

What is EVF?

In freestyle, propulsion comes from the arm pulling against the water. Most amateur swimmers let their elbow drop during the pull (dropped elbow): they pull with the forearm nearly horizontal, reducing the catch surface and force generated.

EVF corrects this: as soon as the hand enters the water, the elbow stays high (near the surface) while the hand sinks and rotates downward. Result: the forearm is vertical, like a paddle, and the contact surface with the water is maximised.

Concrete effect: at the same effort, a clean EVF can cut seconds per 100 m by 3 to 8 seconds depending on your starting level. That's the equivalent of a large cardio block, but with zero extra kilometres.

The 3-step movement

1. Entry and extension: the hand enters the water about 30-40 cm ahead of the shoulder, thumb or pinky first depending on your style, and extends forward (glide) to avoid braking momentum.

1. Catch (the EVF key moment): before the arm starts pulling, the hand sinks downward while keeping the elbow high. The elbow forms a 90-100 degree angle with the vertical forearm. Visualise that you are "grabbing" a ball placed just below your hand.

1. Pull: once the catch is set (high elbow, vertical forearm), pull by engaging the back muscles (latissimus dorsi), not just the biceps. The hand passes under the body to the hip.

The most common mistake: starting the pull before the catch is set. Slow down the catch phase to feel it.

Pool drills to improve

Fist drill: swim with closed fists for 50 m, then open your hands. The feeling of grip on the water becomes immediate. Repeat 4-6 x 50 m.

Fingertip drag: during the arm recovery phase, drag your fingertips along the water surface. Forces the elbow to stay high during recovery, which makes the EVF position easier on the next entry.

Right arm only, pull buoy between the knees: swim only with the right arm (left along the body), 25 m per arm. You immediately feel whether your elbow drops or stays high during the pull.

Working frequency: 2 sessions per week with 400-600 m of drills. Expect 4-6 weeks before seeing a time gain.

Bike FTP: the central number

FTP (Functional Threshold Power) is the maximum power you can sustain for roughly 60 minutes. It sets all your bike training zones and determines your bike segment pacing in an Ironman.

How to test: 20-minute protocol (maximum sustainable effort), then multiply average power by 0.95. Simpler alternative: 2 x 8-minute protocol (95% of the average). Test at the start of each 4-6 week block, never when accumulated fatigue is high.

Normal progression: +3 to 8% per 6-week build block for a serious amateur. If FTP stalls over 2 consecutive blocks: either volume is too low, or recovery is insufficient (too much volume, short sleep).

CSS swimming and threshold run pace

CSS (Critical Swim Speed): swim threshold pace. Standard test: 400 m max effort + 200 m max effort, with 10-15 min recovery between them. CSS = (400 m distance - 200 m distance) / (400 m time - 200 m time). Expressed in seconds per 100 m.

Usage: training sets at CSS pace (e.g. 10 x 100 m at CSS) provide the optimal intensity volume for swimming improvement without excessive fatigue accumulation.

Threshold run pace: equivalent to the pace sustained in a 45-60 min test. Measure with a solo 30-minute time trial or a half-marathon. Recalculate after each 6-week run block.

Healthy progress indicator: if CSS drops by 2+ s/100 m and threshold pace drops by 5+ s/km over a build block, training load is well calibrated.

CTL and TSB: see fatigue before you feel it

CTL (Chronic Training Load) is an exponential average of your training load over 42 days. It represents your built aerobic fitness. An Ironman triathlete targets a CTL of 60-90 at peak (peak week, 3 weeks before the race).

TSB (Training Stress Balance) is the difference between fitness (CTL) and acute fatigue (ATL, 7-day average). A strongly negative TSB (-20 to -30) means you are depleted, with injury risk and degraded performance. A positive TSB (+10 to +25) on race day means you are fresh and performing well.

Reading cadence: once per week, not every day (daily oscillations are noise). What counts: the trend over 3-4 weeks.

Important limitation: CTL and TSB depend on data quality (power meter, HR, RPE). Without a power meter, values are estimated and less precise.

Why your legs feel heavy leaving the bike

After several hours of pedalling, muscle recruitment is dominated by quadriceps and glutes in a closed cyclic pattern. When you switch to running, your nervous system must shift to a different recruitment pattern (hamstrings, calves, hip flexors in extension). This neuromuscular mismatch takes 1 to 3 km to resolve and gradually diminishes with regular brick training.

The second factor is blood redistribution: capillaries optimised for the pedalling position must readapt to the running position within a few minutes. Regular bricks speed up this vascular adaptation.

Two types of bricks depending on your training phase

Short brick (base and build phase): 60 to 90 min on the bike in zone 2, followed by 15 to 30 min running in zone 2. Goal: accustom the body to the recruitment shift without cumulative stress. Recommended frequency: once every 2 weeks in base, once a week in build.

Long brick (peak and specific phase): 3 to 5 hours of cycling at race intensity (zone 3), followed by 30 to 60 min running at target race pace. Goal: simulate actual race effort. 1 to 2 long bricks in the last 8 weeks before the Ironman, no more (high cumulative fatigue risk).

Rule: a brick takes priority over a standalone bike or standalone run session only if you have fewer than 3 bricks under your belt for your race format.

Common mistakes and how to avoid them

Starting the run too fast: the deceptive feeling of lightness in the first 2 minutes can push you to accelerate. Result: a blow-up at km 3-5. Rule: start the run 10 to 15 sec/km slower than target pace for the first 2 kilometres.

Doing bricks every weekend: too many bricks during base phase generates cumulative fatigue without additional benefit. The body needs to recover bike and run adaptations separately. 2 bricks per month in base, 4 in build, 2 (long) in peak.

Ignoring the T2 transition: the ideal training brick reproduces the real transition: unclipping the helmet, removing bike shoes, putting on running shoes. Even 30 seconds of simulation accelerates the automatism on race day.

Why cadence affects energy economy

At constant power, you can hit the same wattage by pedalling at 60 RPM (big gear, high force) or 100 RPM (small gear, low force). The difference: at low cadence, each pedal stroke recruits more slow-twitch AND fast-twitch muscle fibres, accumulates more lactate and fatigues the quads faster. At high cadence, work is distributed across more strokes, each requiring less muscular force, but the cardiovascular cost (HR) increases.

The optimum lies between the two and depends on your profile: runners (endurance profile) often benefit from a higher cadence (85-95 RPM) as their muscles are built for aerobic economy. Pure cyclists or powerful athletes handle 70-80 RPM better without excessive lactate accumulation.

Finding your personal optimal cadence

Simple 3-step test:

1. Perform 3 x 10 min in zone 2 (60-65% HRmax) at different cadences: 70, 80, 90 RPM. Same course or same resistance on a home trainer.
2. Note your average heart rate on each block and your perceived effort (RPE 1-10).
3. The cadence at which HR is lowest for the same power corresponds to your current optimal cadence.

Typical result: most non-cyclist triathletes find their sweet spot between 82 and 90 RPM. Former cyclists can go as low as 75 without penalty. Below 70 RPM, muscular fatigue over long distance becomes a limiting factor for the run that follows.

Cadence on climbs, descents and race day

Climbs: the temptation is to stay seated and spin. Beyond 5% gradient over 2 km+, resistance naturally drops cadence to 60-70 RPM. Accepting this reduction is normal: forcing 85 RPM on a climb costs too much cardiovascular energy. Standing out of the saddle for 10-15 seconds every minute releases the quads without a significant HR spike.

Descents: do not spin freely at 120 RPM to maintain a gear ratio without resistance. Prefer a bigger gear to maintain a productive cadence (75-85 RPM) and recover without stopping pedalling.

Ironman race day: target 80-85 RPM on the flat, tolerate 65-75 RPM on climbs. The goal is to preserve your legs for the marathon: a cadence that is too low over the first 100 km of the bike destroys the quads and amplifies the heavy-leg phenomenon in T2.

What is zone 2 and how to identify it

Zone 2 corresponds to the intensity where you can hold a full conversation without being out of breath, but where you could not sing. In objective numbers: 60 to 72% of your maximum heart rate, or 55 to 75% of your FTP in cycling power.

Physiologically, it is the zone where your slow-twitch muscle fibres (type I, highly oxidative) work at full capacity without recruiting fast-twitch fibres. The lactate produced is immediately recycled by those same fibres and by the heart as an energy substrate. Result: you can sustain the effort for several hours without neuromuscular fatigue accumulation.

What zone 2 concretely develops

Mitochondriogenesis: regular zone 2 training stimulates the multiplication of mitochondria (the energy factories of muscle cells) and improves their efficiency. More mitochondria means a greater capacity to oxidise fat as fuel, therefore more endurance at race pace.

Fat oxidation: at zone 2 intensity, the body uses lipids as the primary energy source. A well-trained athlete can oxidise 0.8 to 1.2 g of fat per minute, meaning 480 to 720 kcal/h without touching glycogen stores. Over an Ironman, this energetic autonomy is the difference between finishing strong and cracking at marathon km 25.

Fatigue resistance: slow-twitch fibres trained in zone 2 are recruited FIRST at all intensities. The better they function, the longer you can hold on before drawing on fast-twitch fibres, which fatigue quickly and do not recover mid-race.

How to integrate zone 2 without getting bored

The grey zone problem: most amateurs systematically train in zone 3 (tempo), which is too hard for deep aerobic adaptations and not intense enough for anaerobic adaptations. Result: a performance plateau and chronic fatigue.

How to confirm you are actually in zone 2: check your HR on your watch. If it drifts above 72-75% HRmax during a 2h+ long session, slow down. The discipline of the first weeks is hard (you seem to be crawling), but this is where the mitochondrial adaptations are built.

Minimum volume to see the effect: 6 to 8 hours of zone 2 per week for at least 8 weeks. Below 4 hours, the adaptations are insufficient for an Ironman preparation. The bike is the ideal tool: 3 h on the home trainer in zone 2 generates the adaptation stress without the joint impact of running.

Compatibility with intense sessions: you can do 2 to 3 intense sessions (threshold, VO2max) per week alongside zone 2 volume. The rule: never two consecutive intense days, and zone 2 volume must represent 70-80% of total training time.

Why double days work

A single 3-hour session is not equivalent to two 90-minute sessions. Double days allow you to accumulate more total weekly volume without creating an unbearable acute stress in a single session. Between the two sessions, you eat, hydrate, and partially recover: the body is exposed twice to the adaptation signal in the same day.

Hormonally, each session creates a peak of GH (growth hormone) and testosterone. Two sessions = two peaks. The adaptive response is therefore superior to a single session of equivalent duration. This is why training camp weeks (morning swim + afternoon ride + evening easy run) sometimes produce spectacular fitness jumps.

Safety rules not to be negotiated

AM session = zone 2 or technique only: the morning session must be low intensity. If you do threshold work in the morning, you arrive empty for the PM session and cannot produce quality. Reserve intense sessions (VO2max, threshold) for one single moment in the day -- never both.

Minimum 4 hours between the two sessions: the body needs at least 4 hours to partially resynthesize glycogen (with a carb-rich meal) and to erase superficial neuromuscular fatigue. Below 3 hours, you arrive still fatigued and the benefit of the double day disappears.

Nutrition between sessions = the keystone: eat 60 to 80 g of carbs + 20 to 30 g of protein within 30 minutes after the AM session. Then a full meal 90 to 120 minutes before the PM session. Without this recharge, the PM will be a zombie session: your body will burn muscle as fuel.

No more than 2 double days per week in peak phase: beyond that, overnight recovery is no longer sufficient to absorb the load. The risk of overtraining and overuse injury rises exponentially.

The best AM+PM combinations for Ironman

Swim AM + Bike PM (2h+): the premier combination. The morning swim is minimally traumatic for joints, activates the cardiovascular system without impact stress, and leaves you fresh for the heavy bike volume in the afternoon. Also works as swim AM + bike-run brick PM (2h bike + 20 min off-bike run).

Gym AM + Long ride PM: in base phase, a functional strength session in the morning (core, unilateral, skipping rope) followed by a long bike or run in the afternoon. Gym does not deplete glycogen, so you arrive intact for the PM session.

Easy run AM + Hard bike PM: the easy morning run (20-30 min zone 1-2) serves as a systemic warm-up and stimulates circulation. The afternoon bike session with intervals will benefit from better vascularisation. Warning: this format only works if the AM run is genuinely easy.

What to never combine: two running sessions on the same day (impact and injury risk too high) and two intense sessions on the same day (supercompensation impossible, counterproductive).

Why mobility matters in long-distance triathlon

Triathlon demands three disciplines with radically different postural requirements. In swimming, a stiff shoulder limits the catch and propulsion -- every stroke compensates with excessive trunk rotation, which fatigues the lower back. On the bike in aero position, a hip without mobility forces a pelvic tilt that crushes the hamstrings and loads the lower back differently. Running after 90 km of cycling, a tight psoas reduces stride length and increases energy cost.

The result: stiffness does not always injure directly, but it forces compensations that, over 8 to 12 hours of effort, accumulate fatigue where it should not be.

The 3 priority zones for a triathlete

Zone 1 -- Hips (flexion + internal rotation): hip stiffness is the number one problem for triathletes who spend a lot of time in the saddle. Limited hip flexion forces lumbar compensation on the bike and reduces stride cadence when running. Useful exercises: 90/90 hip flexor stretch, pigeon pose, deep squat held 60 s.

Zone 2 -- Shoulders (external rotation + elevation): swimming demands full external rotation during the catch phase. A swimmer with rigid shoulders compensates with a dropped elbow -- which breaks the pull. Useful exercises: sleeper stretch, doorway pectoral stretch, band pull-apart.

Zone 3 -- Posterior chain (hamstrings + calves): a short posterior chain limits stride amplitude and increases the risk of Achilles tendinopathy or IT band syndrome. Useful exercises: standing hamstring stretch with bent knee, eccentric calf on a step.

When and how to integrate mobility without spending too much time on it

Mobility does not need to be a separate session. The best windows:

Post-session (5 to 8 min): the ideal window -- muscles are warm, the nervous system is relaxed. 3 to 4 exercises targeted on the zones used in the session. No need for a complete programme: 2 hip exercises + 1 shoulder after a swim-bike session is enough.

Morning on waking (5 min): light joint mobility (shoulder rotations, hip circles, cat-cow) to reduce morning stiffness. No intensity -- just movement.

Deload week: the best time for a longer true mobility session (20 to 30 min). Load is low, the body is less fatigued, and mobility gains consolidate better when the system is not in active recovery mode.

What to avoid: stretching cold before a quality session (risk of muscular inhibition) and prolonged static stretches before a performance test.

Understanding why the triathlete is particularly exposed

The iliopsoas connects the lumbar vertebrae (L1 to L5) to the lesser trochanter of the femur. Its main role: flex the hip (raise the knee towards the torso) and stabilise the lumbar spine.

What happens in aero position: on a bike in a low position (long reach, significant drop), the torso is flexed and the hip remains in permanent flexion between 70 and 90 degrees. The psoas works in isometric shortening throughout the ride -- creating an accumulated tension state. After 5 to 7 hours in aero position (Ironman), the psoas is literally locked in this shortened position.

What happens during run off-bike: from the first running metres, the stride requires complete hip extension (10 to 20 degrees of extension angle). The psoas -- still shortened by cycling -- must lengthen abruptly at each stride. It is this repeated forced stretching that creates micro-inflammation at the insertion or muscle belly.

Typical signals: deep groin pain / anterior thigh, worsened when climbing stairs or lifting the knee. Discomfort at the start of running after a long bike session. Sometimes, a slight limp in the first kilometres of run off-bike.

Prevention: appropriate stretching and strengthening

Priority stretch post-bike (before run off-bike or in the evening): Half-kneeling lunge: rear knee on the ground, front hip flexed at 90 degrees. Tilt the pelvis into posterior tilt (tighten the core, flatten the lower back) BEFORE pushing forward. Hold 60 seconds each side, twice. This is the most effective stretch to re-lengthen the psoas after a cycling effort.

Eccentric strengthening (preventive, 2x/week in base phase): Slow walking lunge: each step = lower slowly (3 seconds) onto the rear knee, hold 1 second at the bottom, rise back up. The psoas works eccentrically (lengthens under load), which is exactly the run off-bike scenario.

Lumbar-pelvic mobility work: Lumbar stiffness worsens psoas tension (compensation). Incorporate 5 min of lumbar mobility (cat-cow, standing pelvic rotation) after each core session.

Bike fitting: excessive drop (handlebars too low vs saddle) increases hip flexion. If you regularly suffer from psoas issues, have your fitting checked by a specialist. Often, raising the handlebars 10 to 15 mm resolves the problem.

What to do when the pain is already present

Acute phase (clear pain, <72h): Stop running sessions and long bike rides. The psoas does not like complete immobility: replace with swimming (moderate hip flexion) or very short cycling (<45 min) in a raised position (high handlebars).

Subacute phase (pain reduced, 3 to 14 days): Progressive return to running on flat soft surfaces, short distances (20 to 30 min). Avoid hills and stairs. Half-kneeling stretch twice per day. No key session before complete disappearance.

When to consult: If pain persists beyond 3 weeks despite relative rest, consult a physiotherapist specialising in sports medicine. The differential diagnosis includes: iliopsoas bursitis, acetabular labrum, inguinal hernia, osteitis pubis. An ultrasound or MRI may be needed to rule out these conditions.

What not to do:

• Push through acute pain (risk of becoming chronic)
• Violently stretch an inflamed psoas (worsens inflammation)
• Ignore cycling volume management (the root cause)

Ascending: technique, posture and effort management

Uphill posture: The natural tendency is to lean too far forward and look at your feet. Correct position: slight forward lean (from the ankles, not by bending the back), gaze fixed 4 to 6m ahead, active arms at 90 degrees to counterbalance leg effort.

Cadence and stride: Going uphill, shorten your stride and increase cadence. Trying to keep the same stride as on flat ground = insufficient power and hamstring overload. Target cadence on hills is the same as on flat ground (160-170 spm for most) but with reduced amplitude. Land under or slightly in front of the hips -- never far in front (heel-striking on uphills = braking + knee overload).

Effort management: In triathlon, hills are not sprinted. Perceived effort is always higher on a climb than on flat ground at equivalent power (gravity adds ~1% energy cost per % grade). During a race, climbing at the same intensity as on flat (same HR or same RPE) means SLOWING pace. Counter-intuitive but the only way not to blow up on the descents and the rest of the course.

Descending: the real danger and how to avoid it

Descending is often more traumatic for the body than ascending. Braking forces (eccentric quadriceps braking) are 2 to 3 times greater than propulsive forces. In Ironman triathlon, a series of long descents after 6 hours of effort can cause severe DOMS that ruin the marathon.

Descending technique:

• Lean the torso back (from the ankles): this reduces impact force on the front leg and allows landing closer under the centre of gravity.
• High cadence, shorter stride: even more important than on uphills. Long stride on descents = hard heel impact = maximum quadriceps load = knee pain and DOMS at end of race. Aim for 165-175 spm, landing flat-footed or on the forefoot.
• Do not brake with your thighs: the natural temptation is to slow down by stiffening the legs (landing hard on the heel far in front). This is exactly what destroys quadriceps. Let inertia do the work, stay relaxed, use cadence to control speed.
• Look ahead: anticipate the terrain 5-8m in front to adjust foot placement.

In Ironman on a hilly course: if you know the course has significant hills, including downhill running in long training sessions is essential. Eccentric quadriceps capacity is developed through specific training.

The Cooper test: protocol, calculation and interpretation

Protocol:

1. Warm up for 15-20 min (easy jog + 4-6 x 20s accelerations).
2. Run for 12 minutes maintaining the highest possible intensity WITHOUT blowing up mid-test. The classic mistake: starting too fast for the first 3 minutes and walking the last 3.
3. Measure the distance covered in metres (400m track or GPS).
4. Complete rest of 10 min afterwards.

VO2max calculation (Cooper 1968 formula): VO2max = (distance in metres - 504.9) / 44.73 Example: 2800m in 12 min -> VO2max = (2800 - 504.9) / 44.73 = 51.3 ml/kg/min

Interpretation for an amateur triathlete:

• < 40: beginner, priority on zone 2 volume.
• 40-50: decent amateur level, improvable.
• 50-60: solid level for finishing an Ironman in < 11h.
• 60-65: elite age-group level, sub-9h Ironman target.
• > 65: elite (rare for athletes over 30).

Test limitations: the formula assumes correct running economy and a rested state. A technically inefficient or fatigued runner will overestimate their limitations. Cooper-estimated VO2max has a margin of error of +-3-5 ml/kg/min vs laboratory.

Alternatives to Cooper: when and why to use them

5 km TT (Time Trial) test -- adapted for triathletes: Run a 5 km flat out (after warm-up), record the time. Approximate formula:

• VO2max ≈ 133.2 -- (13.49 * time in min)

Advantage: more representative of real aerobic capacity than a 12-min effort. Disadvantage: longer effort, more fatiguing.

Vam-Eval test (incremental laps on track): Audio protocol with sound signals (downloadable MP3 file). 2-min stages at increasing speed (8 -> 18+ km/h). More accurate, requires audio equipment. Gives VAM (Maximum Aerobic Speed) in addition to estimated VO2max.

Garmin/COROS/Polar watch estimators: Watches calculate estimated VO2max via algorithms based on HR vs speed. Accuracy: +- 5-10 ml/kg/min compared to lab. Useful for trend tracking (is my VO2max progressing?) but unreliable for an absolute figure.

When to test:

• In BASE phase (months 1-2 of the plan): initial measurement to calibrate zones.
• In BUILD phase (months 3-4): re-test to validate progression.
• Never in PEAK or TAPER phase: intense effort = disruption of preparation.

Maximum frequency: 1 test every 6-8 weeks. Testing more often does not accelerate progress and fatigues unnecessarily.

Dead spots in the crank revolution: where power is lost

A full crank revolution divides into 4 quadrants:

• 0-90 deg (push down): main power phase. Quads and glutes well-activated.
• 90-180 deg (through the bottom): first dead spot. The leg passes through the bottom dead centre without applying net force.
• 180-270 deg (pull up): hamstring and hip flexor contribution. Often under-used.
• 270-360 deg (through the top): second dead spot. Passing through the top dead centre, difficult without strong flexor muscles.

Triathletes on road bikes often pedal in 'squares' (two push strokes, two extended dead zones). 'Rounded' pedalling does not eliminate dead spots, it reduces and smooths the torque curve. Real gain over an Ironman: better energy economy and reduced peaks of muscular tension.

Concrete drills to improve your pedalling

Single leg drills (trainer only): pedal one leg at a time, the other resting on a stable support. The dead spot becomes immediate and identifiable as a 'square' or a click. 3 x 30 sec per leg at the end of an easy ride, twice a week in base phase.

High cadence pedalling (90-110 rpm) in zone 2: a higher cadence penalises dead spots more (less time to 'mask' the dead spot through inertia). 20 continuous min at high cadence during a Z2 ride: if the body 'bounces' on the saddle, the dead spot is poorly managed.

Short, gentle climb work (5-6%) at low cadence (50-60 rpm): the opposite: high force required, dead spots visible through juddering. Alternate 10 min normal / 5 min low-cadence climb.

Power metre feedback: if you have a bilateral sensor (left vs right power separately), monitor the ratio. A ratio >55/45 indicates an imbalance to correct. The goal is not a perfect 50/50 (the dominant leg will always push slightly more), but staying within 52-53/47-48.

Pedalling vs position: what takes priority

A poorly adjusted bike fit cancels out all pedalling technique work. Saddle height is the number one setting: too low = power loss in the quads, too high = pelvic rocking and the leg 'dropping' at the bottom of the stroke.

Practical rule: the leg angle at the bottom of the stroke (6 o'clock on the pedals) should be 25 to 35 degrees (leg almost straight but not locked). Too many triathletes have the saddle too low to 'feel stable': it is a comfort compromise that costs power.

Priority order for pedalling in an Ironman:

1. Correct position (bike fit): non-negotiable foundation
2. Optimal cadence for your FTP (between 80-95 rpm for most)
3. Left/right balance via power meter if available
4. Elimination of dead spots (drills)

Technique work in base phase only. In build and peak phases, maintain the gains through high-cadence drills, do not introduce new changes.

TSS: the cost of a session in a single value

Training Stress Score (TSS) is a rating that quantifies the physiological stress of a session. It combines duration and intensity into a single normalised value.

Basic formula: TSS = (duration in seconds x NP x IF) / (FTP x 3600) x 100. In practice, your software (Garmin, Strava Premium, TrainingPeaks) calculates it automatically once you've entered your FTP.

Concrete benchmarks:

• < 150 TSS: low, rapid recovery (< 24 h)
• 150-300 TSS: moderate, full recovery in 24-48 h
• 300-450 TSS: high, 2-4 days to recover fully
• > 450 TSS: very high (long Ironman ride, 5h+ brick), 4-7 days of recovery

A full Ironman typically generates 700-1,000 TSS depending on level. Hence the exhaustion for 2-3 weeks post-race.

CTL and ATL: chronic fitness vs acute fatigue

CTL (Chronic Training Load) is the exponential average of your TSS over the last 42 days. It's your baseline fitness level, your aerobic capacity built week by week. It rises slowly (weeks of effort) and falls slowly (> 1 week of no training). A serious Ironman triathlete maintains a CTL of 80-130 during build blocks.

ATL (Acute Training Load) is the 7-day average. It's the snapshot of your recent fatigue. It rises fast (3-4 days of high load) and falls fast (2-3 days of rest).

Key relationship: if ATL > CTL by 30-40+ points, you are in a recovery deficit. If ATL < CTL by 20-30 points, you are tapering and your fitness is being released.

Classic beginner mistake: seeing CTL drop during taper and panicking by overloading the last week. That is exactly the opposite of the right behaviour.

TSB: the race-day form indicator

TSB (Training Stress Balance) = CTL - ATL. It's the difference between your accumulated fitness and your recent fatigue. Sometimes called 'form' in TrainingPeaks.

• Negative TSB (-20 or lower): you are fatigued, you are building. Normal build zone.
• TSB between -10 and +5: maintenance state. Good for secondary races.
• TSB between +5 and +25: optimal performance zone. Aim for this window for your A-race.
• TSB > +25: under-loaded, you are resting too much. Risk of losing sharpness and speed.

Target for a full Ironman: TSB between +15 and +25 on race morning. To reach this from a CTL of 100: progressively reduce volume over a 3-week taper while keeping a few short but intense efforts to maintain neuromuscular sharpness.

Limit of the metric: TSB does not account for life stress, illness, or sleep quality. It is a tool, not an oracle.

Why climbs ruin Ironman marathons

On a flat course or with a power meter, effort regulation is natural: speed stays near constant, so does power. On climbs, everything changes:

The perceived effort trap: At equal power, speed drops on a climb. The brain interprets the 'slowness' as insufficient effort and pushes to accelerate. Without a power meter, athletes systematically overspend on climbs.

Intensity spikes and lactate debt: Spending 20-30% above FTP for 3-5 min on a climb doesn't feel bad immediately -- but creates a recovery debt. Over an Ironman with 5-6 climbs, these spikes accumulate. The decoupling between HR and power (cardiac drift) becomes visible at km 80-100: the target power becomes unsustainable even at high HR.

Reference figure: A study on Ironman UK (Earnest 2009) shows that athletes who exceed their target power by > 10% on climbs run their marathon on average 45 min slower than those who stay within that threshold -- at the same bike FTP.

How this varies by course profile:

• Flat course (< 500 m elevation gain): climbs are minor, pacing management is dominated by false flats and wind
• Medium course (500-1500 m elevation gain): climbs are the key driver of power variability
• Mountainous course (> 1500 m elevation gain, e.g. IMSA, IMCH): climb management is the central race challenge

Climbing technique and concrete pacing rules

Pacing rule #1 -- The 5% rule: In Ironman, never exceed FTP + 5% on climbs. If your race target power is 200 W, the ceiling on climbs is 210 W. That's less than what you could sustain, but it's what preserves the marathon.

Pacing rule #2 -- Increase cadence rather than force: On climbs, the natural reaction is to 'push harder' (increase torque, lower cadence). The problem: explosive muscle contractions at low cadence exhaust type II (fast-twitch) fibres -- the same ones you need for running. Counter-strategy: drop to a lower gear BEFORE the climb, maintain cadence >= 75 RPM, and accept going slower. Power comes from the legs without emptying them.

Climbing position:

• Short climbs (< 2 min): stay on extensions if gradient allows, keep aero position
• Long climbs (> 3 min, > 5%): sit up on the hoods/bars, open the chest, deeper breathing rhythm. The aero loss is offset by better muscle recruitment and increased lung capacity
• Don't stand out of the saddle in Ironman except to vary muscle engagement on a very long climb (> 8-10 min) -- standing is glycogen-expensive

Without a power meter -- the RPE scale: On climbs, if perceived effort exceeds 7/10, slow down. If you can still say a short sentence, you're in the right zone. If you can only speak in isolated words, you've overspent.

Managing transitions before and after the climb: Anticipate descents for eating/drinking (hands needed). Approach the climb with a full bottle and a gel available if > 5 min of climbing -- digestion slows after intense effort.

Race hierarchy: A, B, C

A-race (1-2 per year maximum): the race(s) for which you structure ALL preparation. Peak form must land exactly here. Taper starts 2-3 weeks out. You make no concessions on sleep, nutrition or training load in preceding weeks. Example: your season Ironman, or your target Half Ironman qualifier.

B-race (2-4 per year): races that serve to test form, validate nutrition/pacing strategies, or maintain motivation. You adjust the taper (1 week max), recover normally after, then resume training within 5-7 days. You don't exhaust form capital on these.

C-race (as many as you want): pure training sessions in competition. No taper. No specific strategy. You arrive tired if it falls in a training block, you resume the next day as if nothing happened. Useful for open-water swimming, local sprint triathlons, short trail runs.

Building the annual calendar

Annual periodisation logic:

1. Place A-races first. They anchor everything else. Dates are fixed, unmoveable.
2. Position B-races in support. Ideally 4-8 weeks before the A-race (full dress rehearsal), or at the start of a cycle (post-base validation).
3. Insert transition weeks. After each A-race: 2-4 weeks of transition (volume reduced to 40-50%, no sustained intensity). These weeks are when the body repairs accumulated micro-damage and motivation rebuilds.
4. Define preparation blocks. Aerobic base (12-16 weeks), specific build (8-12 weeks), peak and taper (3-4 weeks). These blocks chain together between A-races.

Classic mistake: too many B-races that become involuntary A-races. If you taper 3 times per season, you spend 3 form peaks on secondary races and arrive at your A-race with ordinary form instead of a peak.

Managing multiple A-races in the same year

Two A-races in the same year are possible with good structure, but require at least 10-12 weeks of separation (6-8 weeks of new specific build + 3-4 weeks of peak/taper).

Double Ironman trap in the same season: the 4-6 weeks of post-Ironman recovery + the Ironman-specific rebuild mean that two serious Full IMs in the same year require a minimum 5-6 months of separation. Under 4 months, one of the two will systematically be sub-optimal.

Mixed-distance season (Half + Full in the same year): more manageable. The Half can serve as a B-race 8-10 weeks before the Full. The challenge is not to be swept away by the competition at the Half and staying in 'race-pace session' mode rather than 'give everything' mode.

Simple rule: 1 A-race per 16-20 weeks of specific preparation. Wanting to do more is possible but requires reducing the quality of preparation for each.

Three fatigue levels: don't confuse them

Normal fatigue (2-3 days of recovery): after an intensive block or competition. Performance returns to baseline or slightly above (supercompensation). This is what you're looking for.

Functional overreaching (1-2 weeks of rest): deliberate load accumulation beyond immediate recovery capacity. Performance dips during the block, then rebounds after the deload week. Advanced technique, useful if well managed.

Non-functional overreaching / overtraining (months of recovery): performance does not return even after several weeks of rest. Accompanied by lasting hormonal changes (testosterone/cortisol drop, HPA axis dysregulation). Rare but devastating. Distinguishing it from functional overreaching is difficult: only time (and sometimes blood work) decides.

Warning signals to watch for

HRV (heart rate variability): a progressive HRV drop over 5-7 consecutive days, with no rebound the morning after a normal night's sleep, is the most reliable signal. An app like HRV4Training or Elite HRV in 2 min each morning is sufficient.

Training performance: if your power at the same RPE decreases over 2-3 consecutive weeks (not just one bad day), that is a serious signal. Distinguish passing fatigue (1-2 bad sessions) from extended plateau (3 weeks of regression).

Sleep and mood: difficulty falling asleep despite physical tiredness, night waking, disproportionate irritability, loss of motivation for activities unrelated to sport -- these psychological signals often precede physiological signals by several days.

Resting heart rate: an elevation of 5-8 bpm over several consecutive mornings is a useful complementary indicator (less precise than HRV but easy without equipment).

What triggers the tipping point: volume increase > 10-15% per week, competition block without a deload week, cumulative work/family stress + training volume, < 7h sleep during an intensive training period.

Protocol for exiting overreaching

If you identify functional overreaching:

1. Immediate deload week: volume at 40-50% of normal, reduced intensities (90% of time in zone 1-2, maximum 2 short threshold sessions).
2. Sleep priority: go to bed 30-60 min earlier, eliminate alarms if possible.
3. Nutrition: aim for 8-10 g of carbohydrates/kg/day to replenish glycogen stores and support neuromuscular recovery.
4. Plan review: identify the week where load crossed a critical threshold and correct the structure for subsequent blocks.

If symptoms persist > 2 weeks despite deload: consult a sports physician. Blood work recommended (ferritin, thyroid, testosterone, CRP, vitamin D). True overtraining is rare but real -- better to confirm or rule it out.

Principle: it is better to arrive slightly undertrained than overtrained. An undertrained athlete can finish an Ironman. An overtrained athlete DNFs or gets injured.

Why swim cadence matters as much as technique

Most long-distance triathletes swim at 50-65 strokes per minute (SPM). Elite open-water swimmers are at 70-90 SPM. The gap is not purely a technique issue: it is also a neuromuscular rhythm question.

Too low a cadence (below 50 SPM):

• Forces excessive glide between each pull. In calm pool water this can work. In open water with waves and current, glide turns into lateral drift and lost propulsion.
• Extends the forward hold phase (catch), which fatigues the shoulder over distance.
• Creates gaps in the cycle where the legs sink to compensate.

Too high a cadence (above 85 SPM without preparation):

• Reduces distance per stroke (DPS), which cancels out the frequency advantage.
• Exhausts shoulders and forearms faster.
• Encourages choppy breathing incompatible with a base-pace rhythm.

Optimal zone for non-professional Ironman triathletes: 60-75 SPM.

Diagnosing your current cadence

Manual method (no watch). Swim 50 m at Ironman race pace (comfortable rhythm, breathing every 3 strokes). During one arm, count how many times your right hand enters the water in 15 seconds. Multiply by 4. Divide by 2 to get total SPM (both arms). Or simply: count your complete cycles (right + left) over 20 m in the pool, compare to your previous 50 m.

Watch method. Most current triathlon watches (Garmin Forerunner 955, COROS Pace 3, Polar Vantage) display SWOLF (cadence + SPM) over pool lengths. In open water with lake/OWS mode, measurement is less reliable but gives an order of magnitude.

What you are trying to diagnose:

• Your cadence at session start vs end (drift = fatigue or deteriorating technique)
• Your cadence when focusing on technique vs swimming on autopilot (autopilot reveals true level)
• Your SWOLF evolution over 400 m (low and stable = good, high and variable = inefficiency)

Training cadence in your sessions

The golden rule: increase cadence without reducing DPS. The challenge is not to move your arms faster, it is to maintain the same distance per stroke at higher cadence. This is called efficiency.

Exercise 1: metronome-guided cadence (pool only) Use an underwater metronome app (Finis Tempo Trainer Pro or smartphone app with waterproof earbuds). Set the metronome 5 SPM above your natural cadence. Swim 10 x 100 m maintaining the imposed rhythm. Success criterion: SWOLF equal to or lower than your natural value. Progress by 5 SPM per 4-week block.

Exercise 2: short paddle sprints to activate the neuromuscular system 6 x 25 m at maximum cadence (85-90 SPM) with fins. This is not a power effort, it is a neuromotor wake-up. Recovery 20 s. Do it at session start before your main sets to sensitize the nervous system to high frequency.

Exercise 3: 3+1 (catch-up drill with count) Swim catch-up (wait for front hand to touch the other before pulling), but count cycles: 3 catch-up cycles (slow), 1 cycle at race pace rhythm (target cadence). This contrast helps the brain internalize the difference in timing.

Cadence training frequency: 1 dedicated session per week in base phase, 1 15-min reminder in build/peak. Cadence must not be rushed: shoulder tendon tissue needs 4 to 6 weeks to adapt to higher frequency.

What is the lactate threshold (and why it matters)

The lactate threshold (LT or LT2) is the intensity at which lactate accumulates faster than it is eliminated. In practice, it is your FTP on the bike (60-min all-out power) and your threshold pace running (the pace you could hold for 60 min solo).

Why threshold is so important in long-distance triathlon:

• The bike leg of an Ironman is raced at approximately 75-80% of FTP. The higher your FTP, the faster your absolute speed at the same relative intensity.
• The run leg of a 70.3 is raced at approximately 85-92% of threshold pace. Developing threshold = running faster for the same perceived effort.
• Threshold responds very well to training over 4 to 12 weeks - it is the highest-yield zone for central cardiovascular adaptations (stroke volume, muscular economy).

Physiological signals during a threshold session: you can say 2-3 words but not a complete sentence. RPE 7-8/10. HR around 85-92% HRmax (variable based on daily form). Forced but rhythmic breathing.

Format 1: Cruise intervals (Friel)

This is Joe Friel's reference format (TTB ch.11) for threshold development. Structure:

Bike: 3 to 5 x 8 to 12 minutes at 95-105% FTP, recovery 2 to 3 minutes in zone 1-2. Total threshold volume: 24 to 60 minutes. Run: 3 to 5 x 6 to 10 minutes at threshold pace (10K pace + 10-15 sec), recovery 2 minutes walking/easy jog. Swim: 5 to 8 x 200 m at CSS (Critical Swim Speed), recovery 20 to 30 seconds.

Key principle: short recoveries (less than 3 min bike/run) maintain elevated lactate concentration during the recovery interval, amplifying the adaptation stimulus. Long recoveries (5+ min) allow near-complete elimination - this then becomes a VO2max session, not a threshold session.

6-week progression: start with 3 x 8 min (24 min total), progress to 5 x 12 min (60 min total). Do not increase duration AND intensity simultaneously.

Format 2: Continuous tempo and Format 3: Descending threshold

Continuous tempo (format 2) A single 20 to 40 minute block at 88-92% FTP on the bike (or threshold pace -5% running). Closer to Ironman/70.3 race reality than intervals, it develops the ability to sustain intensity over time.

• Base phase: 1 x 20 min.
• Build phase: 1 x 30 min.
• Peak phase: 1 x 40 min (bike only; running 40 min at threshold is too close to recovery limits).
• Stop signal: HR rising 10 bpm without increasing power/pace = cardiac drift or deep fatigue, stop or reduce.

Descending threshold (format 3) Format for high-load weeks or when form is uncertain. Structure: 3 blocks of decreasing duration with stable or slightly increasing intensity.

• Bike example: 15 min at 95% FTP / 10 min at 100% FTP / 5 min at 105% FTP. 3 min recovery between blocks.
• Run example: 10 min at threshold pace -10 sec / 6 min at threshold pace / 4 min at threshold pace +5 sec.

This format reduces session failure risk (the longest blocks are the least intense) while finishing on a neurally stimulating note.

Frequency: 1 threshold session per week per discipline in build phase, maximum 2 (never 2 consecutive days on the same discipline). In base: 0 or 1 bike threshold session per week, 0 running.

Why triathletes are more exposed

Iron is essential for the synthesis of hemoglobin (oxygen transport) and myoglobin (oxygen storage in muscles). Several endurance-specific mechanisms increase losses and reduce absorption:

1. Mechanical hemolysis: repetitive foot impact during running destroys some red blood cells (footstrike hemolysis). Reduced by 30 to 60% with adequate cushioned shoes.
2. Gastrointestinal losses: intense effort reduces intestinal perfusion and can cause micro-bleeds. Risk increased with NSAID use (ibuprofen, aspirin) during training.
3. Sweating: iron is lost in small amounts in sweat, but cumulated over long volumes, the loss becomes significant (1 to 2 mg/hour of intense effort, ISSN 2018 estimate).
4. Hepcidin: intense effort triggers a post-session hepcidin spike (peak 3h after effort) that temporarily blocks intestinal iron absorption. Consuming iron within 30 minutes post-session (before the spike) optimizes absorption.

Highest-risk profiles: women (menstruation), vegetarians/vegans, high-volume athletes (more than 12h/week), athletes in growth periods.

Warning signs and diagnosis

Early signs (depleted reserves, low ferritin):

• Unusual fatigue beyond 48h post-long session
• Difficulty reaching usual target heart rates at equal effort
• Persistent heavy legs sensation
• Decreased concentration and motivation

Late signs (established iron deficiency anemia, low hemoglobin):

• Abnormal breathlessness at low intensity
• Pale conjunctiva (inside of eyelids)
• Resting tachycardia
• Brittle nails, hair loss

Recommended blood panel (done at season start, then every 3-4 months if risk factors):

• Ferritin (iron reserves): athlete target above 50 ng/mL, alert below 30 ng/mL
• Transferrin saturation (iron mobilization)
• Complete CBC (hemoglobin, MCV, MCHC)
• Optional: hepcidin, soluble transferrin receptor

Do not interpret results alone if hemoglobin is normal but ferritin is low: this picture (latent deficiency without anemia) is common in athletes and still requires nutritional intervention.

Prevention through diet and supplementation

Dietary sources - heme iron (15-35% bioavailable):

• Red meat (beef, lamb): 3-4 mg / 100 g
• Organ meats (beef liver): 6-7 mg / 100 g
• Molluscs (mussels, clams): 5-8 mg / 100 g

Dietary sources - non-heme iron (1-8% bioavailable):

• Legumes (lentils, chickpeas): 3-7 mg / 100 g
• Seeds (chia, pumpkin): 4-8 mg / 100 g
• Firm tofu: 3-5 mg / 100 g

Absorption enhancers: vitamin C (orange juice, raw bell pepper) consumed in the same meal multiplies non-heme iron absorption by 2 to 4.

Inhibitors to avoid in iron-rich meals: coffee, tea (polyphenols), dairy products (calcium), zinc or calcium supplements.

Supplementation (only on medical recommendation with confirmed test): ferrous sulfate 80-160 mg/day in 8 to 12 week courses. Take in the morning fasted or with vitamin C. Frequent side effects (constipation, nausea): split the dose if necessary. NEVER supplement without blood tests - iron excess is toxic and irreversible.

The 4 blocks to analyze: swim, bike, run, nutrition/hydration

Swim:

• Average heart rate vs target (too high exiting the water mortgages the bike)
• Navigation: estimated extra yardage (GPS often imprecise in open water - cross with official time and distance)
• Conditions feel (temperature, visibility) vs specific preparation
• Position in the wave: too far front with insufficient swimming = overexertion and breathlessness; too far back = reduced drafting benefit

Bike:

• Power distribution: normalized power (NP), variability index (VI = NP/AP, target below 1.05 on flat Ironman), intensity factor (IF = NP/FTP, target 0.68-0.72 for Ironman)
• Nutrition plan respected (did you follow your hourly strategy or not)
• Position and possible pain (neck, perineum, feet)
• Average km/h vs weather conditions (wind, elevation) to benchmark real effort

Run:

• Pace spread first km vs last km (a good Ironman run is run at a negative or neutral split)
• Walked portions and why (nutrition, cramps, heat, mental give-up)
• Garmin/Strava lap tour: where exactly did performance drop, correlations with preceding bike kilometers

Nutrition/hydration:

• Actual carbohydrates per hour across each discipline
• Any GI issues and when they appeared vs intake timing
• Pre/post-race weight change if measured (hydration indicator - 1-2% loss = normal, above 3% = significant dehydration)

Building a 3-priority action plan

After documenting the 4 blocks, resist the urge to fix everything at once. Choose 3 levers maximum for your next cycle, ordered by impact/effort:

1. Priority 1 (high impact, moderate effort): usually nutrition (nutritional deficiency destroys performance over distance, and it is 100% correctable through training practice).
2. Priority 2 (medium impact, high effort): the discipline that most impacted total time (often cycling for run-background athletes, or swimming for converted cyclists).
3. Priority 3 (medium impact, medium effort): a race management point (pacing, transition, equipment choice).

Formulate each priority as a measurable behavior: not 'improve cycling' but 'maintain VI below 1.05 across the next 2 preparatory 70.3s'.

Where does 180 come from and what does it actually mean

Jack Daniels, exercise physiologist, observed in 1984 at the Los Angeles Olympics that most elite runners maintained a cadence above 180 steps/min. This figure was then popularized as a universal standard, which it is not.

Reality is more nuanced:

• The observed athletes were running 5000 m and the marathon, at paces very different from Ironman run pace (which is 30 to 60 s/km slower).
• The naturally lower cadence of shorter runners is biomechanical, not a flaw.
• Recent studies (Willy 2012, Hobara 2012) show that increasing cadence by 5 to 10% reduces ground impact forces regardless of the absolute target figure.

The real question is not 'am I hitting 180?' but 'does my cadence minimize energy waste and joint stress at my Ironman run pace?'

How to find and improve your personal cadence

Step 1: measure your current cadence Most GPS watches and Garmin/Polar sensors measure it. Otherwise count single-foot strikes for 30 seconds and multiply by 4. Do it at your target Ironman pace (not sprinting).

Step 2: assess the margin If your cadence at Ironman pace is below 160-165 steps/min, there is likely room for optimization. Between 168 and 180 depending on your build, you are in the normal range. No need to force higher if your running economy is good.

Step 3: progress in 5% steps Do not increase by 20 steps/min at once: neuromuscular adaptations take 4 to 8 weeks. Concrete method:

• 1 session per week with a metronome (free app, set to +5% of your current cadence).
• Duration: 20 to 30 min at easy pace only.
• Progression criterion: hold the target cadence for 20 min without conscious effort before increasing again.

Signs of suboptimal cadence: overstriding with heel strike well ahead of center of gravity = braking with each step. This pattern increases stress on the knee and hamstrings, common in triathlon where cycling pre-fatigues the quadriceps.

How to structure a double day effectively

The benefit of a double day isn't raw volume: it's stimulus frequency. Two 50-minute sessions create two adaptation peaks, and between them, the body begins recovery in a slightly compromised state -- which amplifies hormonal adaptations.

Recommended structure:

• Morning (primary): key session (threshold, intervals, long session). Maximum intensity.
• Evening (secondary): short endurance session (Z1-Z2, 30 to 45 min). Never two intense sessions in one day.
• Nutrition between sessions: carbohydrates 1.0-1.5 g/kg within 30 min post-morning session.
• Rule: space the two sessions by at least 6 hours. Avoid a double day the day before a long session.

Why triathletes avoid strength training (and are wrong)

Classic reasons for avoiding the gym: fear of gaining mass, lack of time, feeling that extra sessions will overload recovery. These fears are understandable but the research is clear: heavy-load strength training (3 to 5 sets of 3 to 6 reps) does not increase muscle mass in endurance athletes, but improves motor unit recruitment and tendon stiffness.

Documented benefits include: 5 to 8% reduction in oxygen consumption at sub-maximal pace (running economy), increased cycling power at threshold and reduced risk of stress injuries (shins, plantar fascia, Achilles tendon).

Priority exercises for triathletes

Lower body (maximum priority): back squat, Romanian deadlift, unilateral step-up, leg press. These exercises target the posterior chain and hip stabilisers, critical zones for running and cycling.

Upper body (secondary priority, especially for swimming): vertical pull (lat pulldown or pull-ups), horizontal row, military press. Avoid heavy bench press that can compress the shoulders and harm swim technique.

Core (integrated, not isolated): dynamic planking (plank with movement, rollout), anti-rotation exercises (Pallof press). A strong core improves force transfer between pelvis and limbs in running and swimming.

Season schedule

Winter phase (November to January): 2 strength training sessions per week, emphasis on heavy loads (3 to 5 reps) and neuromuscular adaptation. This is the ideal period as endurance volume is low and available recovery is higher.

Transformation period (February to March): shift to moderate loads with more reps (8 to 12), integration of more specific exercises (cycling movement simulations, light plyometrics). 1 session per week.

Competition period (April until the race): maintenance only. 1 short session every 10 to 14 days is enough to maintain gains without accumulating residual fatigue. Complete stop 10 to 14 days before the main competition.

Where to position yourself relative to the swimmer ahead

The optimal draft position is not directly behind the swimmer (a position that forces you to abruptly adjust your rhythm with every arm stroke) but slightly offset. Two effective positions:

1. Behind and slightly to the side: your entering hand touches the lead swimmer's toes. The most common position in competition.
2. At the lead swimmer's hip: 'side drafting', especially useful when swimmers are not at the same speed level. Your head passes their hip.

The optimal distance is between 30 and 60 cm. Closer than that risks touching them and disrupting their stroke. Beyond 1 metre, the effect diminishes significantly.

Ironman swim pack tactics

At an Ironman start, the chaos lasts 200 to 400 metres. Two strategies exist:

1. Fast start: you position yourself among the leaders to find clear water and form your pack. Requires 5 to 10 seconds of extra effort at the start, then potentially significant gains.
2. Conservative start: you avoid the blows and fighting, but often leave alone with no available draft. Suited to beginners or athletes who manage their swim pace carefully.

The best approach for a mid-range Ironman: start 15 to 30 seconds after the front pack of your wave, let the water settle, then catch the second group. This group is often more consistent and less aggressive than the first.

Training for drafting

Drafting in competition is trained in the pool and in open water. Basic drill: swim in pairs, the drafter tries to maintain toe-touch contact for 400 metres without modifying their arm rate. The drafter learns to adjust position laterally rather than speeding up or slowing down.

In open water, join group swims where rotation is planned: each swimmer leads for 100 m, then lets others take the front. This develops both the ability to lead (without a draft) and to use a draft (in optimal position).

Also sight regularly: in open water, incorrect navigation destroys the drafting benefit if you must make wide arcs to correct course.

The physiological mechanism

When core temperature rises, the body sends more blood to the skin for cooling through perspiration. This peripheral blood flow reduces venous return to the heart. To maintain the same cardiac output and therefore the same oxygen supply to the muscles, the heart increases its rate to compensate for the falling stroke volume. This is cardiac drift - rate climbs, perceived effort may stay stable, but your margin before the red zone shrinks.

In heat conditions (above 25 degrees Celsius), this drift can reach 10 to 20 beats over the duration of an Ironman. An athlete starting at 140 bpm on the bike may find themselves at 155 bpm at the end of the bike and 160 bpm on the run, without having accelerated by a single watt.

Managing drift during racing

The practical rule: in strong heat, pilot by power (bike) and by pace plus feel (run), not by heart rate alone. If you have a power meter, your watt target remains the stable reference. On the run without GPS pace, a perceived effort out of 10 is a better guide than HR when temperature exceeds 28 degrees Celsius.

If you pilot by HR regardless, add 5 to 10 bpm to your target zones per 5 degrees above 20 degrees Celsius (Friel empirical approximation). In practice, if you target 140-145 bpm at 20 degrees, aim for 145-150 bpm at 25 degrees, 150-155 bpm at 30 degrees.

Preventing drift: hydration and cooling

Cardiac drift is partly preventable. Two levers: hydration and active cooling. On the bike, drink 500 to 750 ml per hour with electrolytes (sodium as the priority - intense sweating eliminates 1 to 2 g of sodium per litre). Do not rely on thirst alone in strong heat: the thirst signal often lags behind actual dehydration.

Active cooling: on the bike, wet the back of the neck, forearms and crown of the head at feed stations. On the run, pour cold water over your head and grab ice if available. Each degree of lower core temperature reduces drift by a few beats. These simple actions can maintain a more stable HR over the final 4 hours of an Ironman in 30 degree heat.

Why the heavy legs after cycling

After intense cycling, your muscles have been engaged in a seated position with specific motor coordination. When you transition to running, the neuromuscular system must recalibrate for an upright position and different stride pattern. This recalibration delay (15 to 30 seconds up to 2 minutes depending on level) is what we feel as heavy legs.

Simultaneously, blood redistribution (from seated to vertical axis) and oxygen must reallocate to different muscle groups. Lactate accumulation during cycling also plays a role. The good news: this phenomenon reduces drastically with specific brick training, which accustoms the body to this transition.

Structure of an effective brick

Short brick (beginner): 30-45 min tempo ride + 10-20 min run. Goal: accustom the body to transition, not performance. Do once per week in build phase.

Race simulation brick (intermediate): 60-90 min cycling at race intensity, quick transition, 20-30 min running at race pace. Goal: test pacing strategy and the exact physiological feel of race day. Do 2 to 3 times in the 6 weeks before competition.

Ultra-short brick (technique): 15 min very intense cycling (Z4-Z5 interval) + 5-10 min running. Excellent for simulating high-intensity bike exit and intra-transition gap. Can be inserted after a normal cycling session.

Common mistake: doing your first brick too close to competition. The brick must be integrated regularly throughout preparation, not only in taper week.

The physiological adaptations to heat

With 10 to 14 days of regular heat exposure, your body develops specific adaptations: (1) Plasma volume increases by 5 to 12% (more fluid blood, better thermoregulation). (2) Sweating threshold lowered (you sweat earlier, more efficiently). (3) Heart rate at a given intensity decreases (heart works better in heat). (4) Sodium lost in sweat reduced (better electrolyte performance).

These adaptations are specific and lost in 2 to 3 weeks without exposure. If your target race is in heat, plan acclimatisation in the 14 preceding days.

Practical protocols according to your context

If you live in a cold zone and race in a hot zone (e.g.: triathlon in Spain):

Option 1 (passive): sit in a sauna for 20-30 min after a training session, 5 to 7 consecutive days. Effective, no second sports session required, accessible. Elevated heart rate = signal of effectiveness.

Option 2 (active with extra clothing): easy sessions (Z1-Z2) with additional warm clothing to simulate heat. Less effective than sauna for isolated adaptation, but combines training + heat.

Option 3 (early travel 10 days out): if budget allows, arrive on location 10 days before the race. Real acclimatisation in race conditions is most effective.

Hydration: increase sodium intake by 500 to 1000 mg/h additionally during hot training sessions. Do not rely only on thirst - it is delayed in heat.

Volume and intensity mistakes

Mistake 1 - Too short taper: the minimum effective taper for a 70.3 is 10-12 days, for an Ironman 21-28 days. A 4-day taper before an Ironman is a common mistake among self-coached athletes. Physiological adaptations (glycogen refilling, muscle rebuilding, plasma volume) take time.

Mistake 2 - Cutting all intensity: the real taper maintains 80-90% of usual intensity, but reduces VOLUME by 40 to 60%. A short high-intensity session (30 min with brief intervals) in mid-taper week reminds the body of its optimal functioning and avoids 'taper torpor'. Without any intensity, you will arrive at the start with cotton legs.

Mistake 3 - Adding new activities: taper week = zero new sport, zero hiking 'to relax', zero intensive tourist exploration if you have arrived on location. Beginner triathletes systematically underestimate the fatigue from pre-race visits.

Psychological and behavioural mistakes

Mistake 4 - Changing nutrition in taper: carbohydrate loading is valid but poorly executed. It is not about 'eating pasta every day'. True carb loading lasts 2-3 days, not the whole week. And changing nutrition on race day (new energy drinks, new food) is a critical mistake - your gut is not in 'experiment mode' on race day.

Mistake 5 - Over-analysing body signals: heavy legs at the start of taper are NORMAL and GOOD. It is the sign the body is reconstituting. Fatigue felt during taper is different from training fatigue - it is temporary, it disappears D-2.

Mistake 6 - Not sleeping enough the 3 nights before (vs the night before): the night before the race, most athletes barely sleep (stress, 4am wake-up). This is normal and acceptable IF the preceding 3 nights have been restorative. The sleep reserve D-3 to D-1 is what matters.

Mistake 7 - Ignoring weather and not adapting: you prepared a race plan for 20 degrees and it is 35 degrees on race day. Adapting pace in real time is a skill, not a concession. Refusing to slow down by 5 to 10% in extreme heat systematically leads to heat stroke or hitting the wall.

Crocodile sighting technique

Classic sighting (lifting the head before breathing) creates a trough in the water, sinks the legs, and breaks rhythm. The optimal technique is the crocodile sight: lift just the eyes above water during the pull phase, without lifting the chin, then turn the head to the side to breathe as usual.

Precise sequence: right arm pull, in the final phase before the hand exits the water, lift the eyes and lower forehead (not the chin) for 1 to 2 seconds, identify the visual landmark, lower the head back in the water while turning it to the side to breathe normally. All in 1 to 2 seconds, inserted in a normal swim cycle.

Frequency and landmark selection

How often to sight? In training: every 6 to 10 strokes. In official race in normal conditions: every 10 to 15 strokes. In heavy swell: every 6 strokes. Too frequent sighting slows you as much as too rare sighting.

Which landmark to use? Buoys are often difficult to see from water level. Look for static terrestrial landmarks at the top of the horizon: a tower, a building, a flag. Identify these landmarks before the race (during briefing or reconnaissance).

In a pack: follow the feet of the swimmer ahead (draft = 20 to 30% less effort) and only sight when the group changes direction.

Sighting-specific training

Sighting is trained like the rest. In the pool: place a brightly coloured object on the pool edge and practise crocodile sighting every 10 strokes, aiming at it. The goal is that the eye lift is automatic and costs nothing in concentration.

Reference exercise: swim 400 m with eyes closed in a 50 m pool, guiding yourself only by touching the lane lines. Very instructive for understanding how much you naturally drift.

Open water sessions: do at least 3 to 4 sessions before an important race, ideally on the site or a similar body of water. An athlete who has only swum once in open water can easily lose 5 to 10 minutes on the swim alone through deviation.

Wind effects on power and speed

Riding into headwind requires between 20 and 60% extra power depending on wind speed, compared to calm conditions. A 30 km/h headwind on flat ground requires as much power as climbing a moderate hill.

The tailwind effect is asymmetric: it increases your speed but proportionally less than the headwind slowed you down. Riding into a headwind then tailwind on an out-and-back course will always cost you time compared to calm, even if it intuitively seems like it balances out.

Effort management strategy

Basic rule: maintain constant POWER, not constant speed. Into headwind, your speed will drop - this is normal and expected. Do not try to maintain speed by massively increasing power (you will drain your reserves for nothing).

Strategy for an out-and-back course: if headwind is on the way out, it will be tailwind on the way back. Conserve energy in the first half: ride at 90 to 95% of your FTP into the headwind. On the return, if legs allow, go to 100 to 105%. Result: better overall time than pushing maximum into the headwind.

Position and equipment in wind

Aero bar position reduces aerodynamic resistance by up to 25% compared to sitting upright. In strong wind, the difference is even more pronounced. Use aerobars systematically in wind if you have them.

Crosswind: the most dangerous for balance. On descents in strong crosswind, stay with hands on top of handlebars (not in aero position) for stability. Deep-section wheels (discs, 80mm and above) are very sensitive to crosswinds: if you are not experienced, a 50mm or standard wheel is safer.

Preparation: check weather the evening before and morning of race day. Identify exposed sections on the map (beaches, plateaux, open countryside areas).

Physiology of high vs low cadences

High cadence (95-110 RPM): less muscular load (quads, glutes), more cardiovascular load (heart rate rises). Recommended for athletes with a strong cardiovascular profile and for preventing muscular fatigue over an Ironman.

Low cadence (70-80 RPM): more muscular load, lower heart rate, often better mechanical efficiency on flat terrain. Risk: accumulated muscular fatigue that impacts running. Studies on Ironman show that athletes who pedal too slowly (under 80 RPM) have on average worse run performances.

Recommended range for Ironman

The range recommended by most specialists for the bike leg in long-distance triathlon is 80-95 RPM on flat terrain. On climbs: 65-80 RPM standing or seated in force depending on gradient and length.

Untrained natural cadence (the one you adopt without thinking) is often too low. Specific cadence training (5-min sets at 95-100 RPM in zone 2, then return to natural cadence) progressively raises your comfortable RPM. A bike computer with cadence sensor is a prerequisite for working on this seriously.

Managing cadence at the end of the bike

In the last 20 to 30 km of the bike leg in triathlon: progressively increase cadence by 5 RPM (85 to 90 to 95) while reducing the gear ratio. The goal is to prepare muscles for running by activating slow-twitch fibres (endurance) rather than fast-twitch fibres (force).

This technique reduces the dead-legs phenomenon in T2. You will exit the bike with a sensation of lighter legs. The cadence increase often implies a temporary heart rate rise: this is normal, it will decrease in the first running kilometres.

Proven benefits for triathletes

Injury risk reduction: common triathlon injuries (iliotibial band syndrome, Achilles tendinopathy, groin pain, swimmer's shoulder) are linked to muscular imbalances and weakness of stabilising muscles. Strength training corrects these imbalances more effectively than training volume alone.

Running economy: research shows that 10 weeks of functional strength training improves running economy by 4 to 8% in endurance runners. For long-distance triathlon, this directly impacts cycling watts and running pace.

Priority exercises

Squats and lunges: strengthens quads, glutes, knee stabilisers. Foundation for cycling and running. Start without load (bodyweight) then progressively add weight.

Core stability (plank, side plank, hollow body): central body stability is the link between power generated by legs and propulsion in running and swimming. 3 x 30-45 seconds per exercise.

Romanian deadlift: strengthens hamstrings and glutes. Protective for the Achilles and hamstrings. Must be done with perfect technique (flat back, weight close to body).

Pull-ups and rowing: back muscles for swimming. Crucial for athletes whose swim is the weak point. 3 x 8-12 repetitions.

When to integrate strength training in the season

Base period (autumn/winter): 2 to 3 strength sessions per week. Reduced triathlon volume. This is the ideal window to build a strength foundation and correct imbalances.

Specific period (spring): 1 to 2 sessions per week, more functional exercises (dynamic core, light plyometrics). Less load, more execution speed.

Pre-competition period (8 weeks before): 1 session per week only for maintenance. No new exercises or maximum loads.

Race week: complete stop. Strength training DOMS the night before an Ironman is the mistake to avoid absolutely. Last strength session at J-15 minimum.

Understanding lactate threshold

The lactate threshold corresponds to the intensity beyond which lactate production exceeds the body's capacity to eliminate it. Below the threshold, effort is sustainable for a long time (zone 1-2). Above it, fatigue accumulates rapidly (zone 4-5).

In long-distance triathlon, high-performing athletes cycle at 80-90% of their cycling lactate threshold during the entire bike leg, then run between 85 and 95% of their running lactate threshold. Pushing this threshold higher is therefore directly linked to a better race time.

How to measure it approximately without a lab: 30-minute test at maximum sustainable sustained effort. Average power or pace over the last 20 minutes corresponds to your FTP (Functional Threshold Power/Pace), a practical approximation of lactate threshold.

Key sessions for developing threshold

Threshold intervals (classic session): 3 to 5 x 10 minutes at 95-105% of lactate threshold, 3-minute zone 1 recovery between each. Total: 30 to 50 minutes at threshold. Frequency: maximum twice per week, during the specific period.

Tempo run: 20 to 40 minutes continuously at 90-95% of threshold, within a longer session (after warm-up and before cool-down). Less intense than intervals but easier to integrate in high volume.

Long intervals (for advanced athletes): 2 x 20 minutes or 3 x 15 minutes at 95% of threshold. Demanding session, to be placed at the start of the week with at least 48h recovery afterwards.

Integrating threshold work into Ironman preparation

Base period (20+ weeks before race): a maximum of one threshold session per week per discipline. Zone 2 volume should dominate (80% of time). Too much threshold too early burns the nervous system and prevents aerobic adaptations from fully developing.

Specific period (8 to 12 weeks before race): 2 threshold sessions per week (1 cycling + 1 run or swim). Threshold should represent 10 to 15% of total volume. Common combination: long cycling session at the weekend + tempo run session mid-week.

Tapering phase (3 weeks before): reduce threshold sessions without eliminating them entirely. 1 short threshold session every 5-7 days is enough to maintain adaptations without accumulating fatigue.

Why legs feel heavy after cycling

When you pedal, your quadriceps dominate the movement (downward push). When you run, your hamstrings and glutes dominate (backward push). The transition causes a neuromuscular delay: the central nervous system must reapply the running motor pattern, which takes 10 to 20 minutes depending on your adaptation level.

Additionally, the cycling position (bent back, flexed hips) shortens the hip flexors. In the first kilometres of the run, these muscles pull forward and disrupt the stride. Brick training teaches the body to release these muscles faster.

The 'brick legs' phenomenon (feeling double the weight in the first km of the run) disappears completely after 4 to 8 well-constructed brick sessions during the season.

Structure of an effective brick session

Short brick (1h-1h30): 45 to 60 min cycling at moderate pace (70-75% FTP), then 15 to 20 min running at race-day target pace or slightly above. This type of brick is done 1 to 2 times per week during specific preparation.

Long brick (3h-4h): 2h30 to 3h cycling with the last hour at race intensity, then 30 to 45 min running at target race pace. This brick simulates the end of the bike and the start of the run in near-competition conditions. Do once every 2 to 3 weeks.

Ironman transition brick (specific): 4h to 5h cycling with simulated nutrition fuelling (gel every 30 min), then 30 to 60 min running at Ironman first-hour run pace. This brick tests your nutrition strategy and leg management simultaneously.

The real benefit of the brick is not the session itself, it is repetition across the season (4 to 8 well-executed bricks > 20 sloppy bricks).

How altitude improves performance

At altitude (1500m and above), the partial pressure of oxygen decreases. To compensate, the body produces more natural EPO (erythropoietin), which stimulates red blood cell production. More red blood cells = more oxygen transported to muscles = better aerobic capacity.

In practice for an amateur: a 5 to 10% increase in haemoglobin is achieved after 2 to 3 weeks of continuous altitude. These benefits persist 4 to 8 weeks after return to sea level before gradually dissipating.

Altitude does not replace training: an under-prepared athlete who goes to altitude will return more fatigued than improved. Altitude amplifies the benefits of good training, it does not create them.

Timing and duration of an altitude camp before competition

Optimal return rule: return from altitude either within 72 hours before competition (benefits not yet amplified but fatigue neither), or 3 to 4 weeks before competition (maximum benefits, fatigue dissipated). The zone to avoid: returning between D-14 and D-4 before competition (altitude fatigue still present, benefits not yet maximal).

Minimum effective duration: 10 days (but 2 weeks is the norm, 3 weeks the optimum). Below 10 days, haemoglobin adaptations are insufficient.

Target altitude: between 1800m and 2500m. Below 1800m, the stimulus is insufficient. Above 2500m for a non-acclimatised person, fatigue and decreased training intensities counterbalance the benefits.

For an amateur preparing for an Ironman in May-October: an altitude camp in March-April (3 weeks) is the optimal option. Classic destinations: Sierra Nevada (Spain, 2320m), Font-Romeu (France, 1800m), St-Moritz (Switzerland, 1800m).

What really changes in open water

Navigation: in the pool, lane lines guide you. In open water, you must lift your head every 6 to 10 strokes (sighting technique) to orient yourself relative to a buoy or a fixed point on the shore. Each sighting costs energy (rhythm disruption, increased drag). A beginner triathlete who sights every 4 strokes will fatigue 20% faster than in the pool.

Mass start: the start phase with 50 to 500 athletes simultaneously is the most stressful part of triathlon for the majority of beginners. Physical contact, splashes, blockages, turbid water. Those who have never simulated it in training often panic in races.

Temperature and wetsuit: below 24 degrees, the neoprene wetsuit is allowed. It provides buoyancy (you ride higher in the water, better position) and thermal insulation. But it creates shoulder constraints: swimming in it for the first time in a race is a mistake.

5-session open water programme before your first triathlon

Session 1 (acclimatation): 20 to 30 minutes of continuous swimming without time pressure. Goal: familiarise yourself with the open water sensation, practice sighting every 8 strokes, identify your sensations with the wetsuit. No intensity, just discovery.

Sessions 2-3 (navigation): swim following a triangular course (buoys or natural cardinal points). Practice turning around a buoy. Swim in 'draft' (in another swimmer's wake approximately 1m behind) to feel the buoyancy advantage.

Sessions 4-5 (race simulation): simulate a mass start with other swimmers. Practice start positioning: neither on the inside (the most intense) nor too far outside (the longest). The side opposite to your breathing side is often better placed to avoid contact.

Basic rules for double sessions

Minimum interval between sessions: 4 hours for moderate intensity sessions. 6 to 8 hours if one of the two sessions is high intensity (threshold, VO2max, sprint). The logic: you need at minimum 2 to 3 hours of post-session digestion and 2 to 3 hours of energy substrate (glycogen) reconstitution before re-stimulating the same system.

Never do two high-intensity sessions on the same day (except very specific protocols like 'shock week' in training camps). The standard sequence: quality session in the morning (technique, short threshold, or specific strength) + extensive session in the evening (base endurance, low-intensity volume).

Prioritise the morning session: morning session quality is generally superior because the athlete is rested. The evening session serves to accumulate volume. If you are forced to cancel one session during the day, cancel the evening session, not the morning one.

Nutrition between the two sessions: the metabolic window

Within 30 to 45 minutes after the first session, the body is in a supercompensation window: muscles absorb glucose and amino acids at 3 to 4 times the normal rate. Not eating in this window is the main recovery error for athletes doing double sessions.

Recommended intake within 30 minutes post-session: 0.4 to 0.6 g of carbohydrates per kg of body weight + 20 to 30g of protein. For a 70 kg athlete: 28 to 42g of carbohydrates (1 banana + 1 portion of oats) + 20 to 30g of protein (200g of fromage blanc or 2 eggs + 1 portion of Greek yoghurt).

Between the two sessions (if the delay is 4 to 6h): a complete balanced meal (complex carbohydrates + protein + vegetables) 1h30 to 2h before the second session. Avoid heavy fat meals within 3h before the second session (slow digestion, possible gastric discomfort during effort).

The 5 files to analyse after an Ironman

1. Bike file (Garmin Edge or computer): average power, normalised power (NP), variability index (VI = NP/average power, target <1.05 for Ironman), average and maximum heart rate, cadence. The NP/FTP ratio (Intensity Factor) should be between 0.68 and 0.73 for a well-managed Ironman. Above = bike too hard, run will suffer. Below = bike too conservative, you left minutes on the road.

1. Run file (GPS watch): breakdown per km. Look for where your pace started to deteriorate (first km slower than planned) and the magnitude of deterioration (how many seconds per km you lost compared to your target pace). A run that deteriorates by more than 30 seconds per km between the first and last 10 km indicates either a too-hard bike, poor heat management, or a failing nutrition strategy.

1. Official timing: official splits per discipline and transitions. Compare your T1 and T2 times with the median for your age group. If your transitions are 1 minute or more slower, this is an easy lever to work on.

Identifying your 3 main improvement levers

3-lever method: after analysing the 5 files, identify the 3 areas where the delta between your performance and the median performance in your age group is largest. These are your priority levers for the next season.

Examples of common levers: (1) Insufficient bike FTP → more work in zones 3-4 this winter. (2) Run that collapses after km 25 → longer brick training + improved bike nutrition management. (3) Slow transitions (+90s vs median) → transition simulation in training.

What you should NOT do: improve your strongest lever. If your swim is already in the top 30% of your age group, investing more time in swimming is poor ROI. Ironman is a global optimisation discipline: the marginal gain on your strong discipline is small, the gain on your weak discipline is potentially enormous.

Write the plan: after the 3 levers are identified, formulate 1 measurable objective for each lever for the next season. Example: 'Increase my FTP from 280 to 310W by 01/04 via 3 threshold sessions per week on the bike this winter.'

NP and IF: what your average power doesn't tell you

Average power (AP) on an outdoor bike session is often misleading. A 2-hour session with 60% of the time at 280W and 40% at 0W (descents, traffic lights) gives an AP of 168W - which suggests a very easy session when metabolically it was very hard.

Normalised Power (NP) corrects this bias. It weights variable efforts by applying a formula that reflects the real metabolic cost (4th power of 30-second smoothed data). In the above example, NP would likely be 255-265W - much more representative of the actual effort.

Intensity Factor (IF) = NP / FTP. An IF of 0.75 corresponds to a base endurance session. An IF of 0.85 is a moderate to sustained long ride. An IF of 0.90+ is a threshold session. An IF of 1.05+ is a race or maximum test effort.

Quick reading rule: IF < 0.75 = recovery/easy endurance. IF 0.75-0.85 = moderate endurance (ideal Ironman zone for a long ride). IF 0.85-0.95 = tempo threshold. IF > 0.95 = high intensity. If your IF on a long Ironman-prep ride is 0.92, you pushed too hard.

TSS: the universal currency of bike training load

Training Stress Score (TSS) = (duration in seconds x NP x IF) / (FTP x 3600) x 100. More simply: 1 hour at FTP = 100 TSS. A 5-hour Ironman long ride at IF 0.75 = approximately 280 TSS.

Reference benchmarks: 50 TSS = light session (creates no significant fatigue). 100-150 TSS = moderate session (fatigue next day, recovered in 24h). 200-300 TSS = long session (fatigue 36-48h, significant training load). 400+ TSS = extreme session or Ironman race day.

Practical application: if your total weekly bike TSS exceeds 600-800 TSS for 2 consecutive weeks without an easy week, you are accumulating a fatigue debt that is difficult to repay before race day. CTL (Chronic Training Load) is the 42-day rolling average of daily TSS: it should be between 80 and 120 for a well-trained Ironman athlete.

Common pitfalls: (1) calculating TSS based on average power rather than NP = systematic underestimation. (2) ignoring the gap between perceived effort and TSS: a windy ride at 180W effective power can give 200 TSS when you only pedalled at 70% of your FTP on the climbs.

Braking and cornering technique in the rain

Braking distance on wet road is 2 to 4 times longer than on dry road, depending on the condition of brake pads and surface. On a triathlon bike with carbon brakes or standard rim brakes (non-disc), the difference is even more pronounced.

Absolute rule in the rain: anticipate stopping points 3 times earlier than in dry conditions. Never lock the rear wheel in a corner (immediate loss of control). Brake in a straight line BEFORE the corner, not during.

Cornering technique in the rain: (1) enter the corner wider than usual (reduced outer-inner-outer trajectory), (2) weight evenly distributed on both wheels (do not lean excessively), (3) cranks at the 3h-9h position (parallel to the ground) - never a low crank in a corner, (4) ride on the central part of the road (edges and road markings are extremely slippery).

Warning signals to recognise: shiny road surface (soil oil film + first rain = maximum danger in the first 20 minutes), wet leaves on road (slipperiness similar to ice), metal manhole covers.

Thermoregulation in cold weather: the cycling clothing paradox

The cold weather cycling paradox: you pedal and sweat (warm core body), but your skin is exposed to the headwind which amplifies heat loss. A headwind at 30 km/h at 5°C external creates a perceived temperature of -5°C on exposed skin.

Adapted layer system: (1) technical base layer (moisture evacuation) - body-hugging, (2) light insulator (softshell gilet or midlayer depending on intensity), (3) waterproof windproof outer layer (mandatory below 10°C with wind). Thermoregulation is done by opening/closing the windproof zip, not by removing layers.

Critical zones to protect first: hands (windproof gloves below 12°C, warm gloves below 5°C), knees (long cycling shorts below 15°C), neck and ears. The head loses 40-45% of body heat - always a cap under the helmet in cold weather.

Post-session rule: change your wet clothing within 10 minutes of stopping the effort. Wet cold perspiration combined with the cessation of muscular heat production creates a hypothermia risk within minutes in winter.

Physics of buoyancy and impact on your swimming

Archimedes' buoyancy force is directly proportional to fluid density. In salt water (density 1.025 vs 1.000 for fresh water), your body is pushed upward with 2.5% additional force. Practical result: your position in the water changes.

Two types of athletes react differently: (1) athletes with low body fat percentage (cyclist-runner type swimmers, <10% body fat): the difference is almost imperceptible, as they already sink little in fresh water. (2) athletes with higher body fat (>18-20%): the difference is very pronounced - their position in salt water is so high that they must consciously immerse their shoulders more to get effective traction.

The wetsuit amplifies the difference: in salt water + wetsuit, you are very high, which can paradoxically reduce your swimming efficiency if your technique is adapted to swimming 'in' the water rather than on its surface.

Technical adjustments for salt water swimming in competition

In salt water competition without wetsuit (when temperature exceeds 24.5°C and wetsuit is banned in Ironman): your position is higher than usual, which reduces frontal resistance. The counterpart: your catch (the water entry phase) must be deeper to find stable water. Correction exercise: think 'enter the hand far forward and wait until it is 20-25 cm deep before pulling'.

In salt water competition with wetsuit: very high position. To avoid swimming flat like a board, pay extra attention to your shoulder rotation (35-45° minimum axial rotation) and your stroke rate (slightly higher than in a pool to maintain traction in very unresistant water).

Over-buoyancy mismanagement signal: your ankles come out of the water and you create hydrodynamic drag. Correction: think 'press your sternum into the water' (vs thinking about your legs) to rebalance your horizontal position without exhausting your legs.

The real advantages of a club that most people underestimate

The club's main advantage is swimming quality. Swimming alone in a lane inevitably leads to technical degradation over 18-24 months: your errors are not corrected, bad habits strengthen. A swimming coach observing you twice a week can identify in one session a problem that would have taken you 6 months to self-diagnose.

The second advantage is the psychological anchoring effect of group sessions. When you have a scheduled slot with other athletes, your session completion rate is 30 to 40% higher than for a planned solo session. Over an annual plan of 600 sessions, that is 180 to 240 additional sessions actually completed.

The third advantage is access to field knowledge: club members have accumulated years of local knowledge about routes, races, service providers (physiotherapist, nutritionist, bike fitter). This knowledge is rarely documented online.

Major club limitation: group sessions are often calibrated to the median athlete of the group, not your individual physiological profile. A club 'high intensity' swim session may be too easy for a strong swimmer and too hard for a weak swimmer.

The optimal hybrid model for the long-distance triathlete

The model that maximises both training quality and scheduling flexibility for long-distance triathletes with a full-time job:

SWIMMING with the club (2x per week mandatory): you benefit from technical feedback and psychological anchoring for the most technical discipline. However, if the club session does not match your programme (too long, wrong intensity), swim your own programme while staying in the club's lane (you benefit from the environment without suffering the unsuitable programme).

CYCLING solo or in level groups (depending on availability): informal cycling groups (non-club) are often better matched in level than club sessions. Solo cycling with a turbo trainer for quality sessions gives perfect intensity control.

RUNNING solo systematically: running in a group alters your effort perception (you accelerate on climbs to avoid dropping, you slow on descents for caution). For quality sessions (intervals, tempo), solo is superior. Long distance group runs are possible if paces are similar.

Why brick legs happen and how to adapt to them

The cause is neuromuscular, not cardiovascular. On the bike, the glutes, quads and calves work in closed cyclic mode (cyclic pressure, limited amplitude). Transitioning to running, muscle recruitment changes radically: hamstrings, calves and hip flexors are engaged differently. The brain must reconfigure the motor pattern, which takes 1 to 3 km depending on your adaptation level.

The good news: this recruitment improves quickly with repetition. After 8 to 12 brick sessions during a preparation season, brick legs often last less than 500 metres. The adaptation is specific: only brick sessions teach it, solo bike rides and solo runs alone do not develop it.

How to structure brick sessions throughout the season

BASE PHASE (20+ weeks before the race): short brick 2h bike + 15 min run at conversational pace. The objective is not intensity but neuromuscular adaptation. 1 brick per week is sufficient.

SPECIFIC PREPARATION PHASE (8 to 12 weeks before the race): long bricks 3h bike + 30 to 45 min run, including the last 20 minutes at target Ironman pace. Add 1 micro-brick of 15 min bike + 5 min run acceleration to practise the fast transition sensation.

RACE SIMULATION WEEK (4 to 6 weeks before the race): 4h bike + 1h run at Ironman pace. This session replaces your long bike ride. It is the most important session of your preparation after your FTP test.

GOLDEN RULE: the run portion of the brick is run at target Ironman pace or slower. A brick where you run fast at the end of the bike does not simulate the race, it creates unnecessary fatigue.

High cadence vs low cadence: the real trade-off

High cadence (90-100 RPM) reduces the muscular load per revolution (less force per pedal stroke) but increases the metabolic cost in oxygen and cardiovascular demand. It better preserves the quads for running, which is the main argument in triathlon.

Low cadence (70-80 RPM) increases the muscular load per pedal stroke (requires more force) but may be more metabolically efficient for some athletes, particularly those with high VO2max and developed muscular strength.

Research (Vercruyssen et al. 2001, Brisswalter et al. 2000) shows that endurance triathletes run more efficiently after a cycling phase at high cadence (85-95 RPM) than after a cycling phase at low cadence (65-75 RPM). The reason: high cadence reduces the metabolic shift from slow-twitch to fast-twitch fibres on the bike, preserving the former for running.

Which cadence to adopt based on your profile

GENERAL IRONMAN RECOMMENDATION: 85 to 95 RPM on flat terrain, 75 to 85 RPM on climbs. Avoid dropping below 75 RPM for more than 5 minutes: this is the threshold where quad engagement begins to seriously compromise the run.

HOW TO FIND YOUR OPTIMAL CADENCE: during a long ride (3h), spend 30 minutes at 75 RPM, 30 minutes at 85 RPM, 30 minutes at 95 RPM, at the same normalised power. Note your heart rate, perceived effort (RPE) and especially the quality of your first 15 minutes of running immediately after. Your optimal cadence is the one that produces the best transition run.

ADAPTATION TAKES TIME: if you normally pedal at 75 RPM, moving to 90 RPM causes a heart rate increase of 5 to 10 bpm in the first weeks. Neuromuscular adaptation takes 6 to 8 weeks to become natural. Do not change your cadence 3 weeks before an important race.

What aerobic base is and why it takes time

Aerobic base is the capacity of your cardiovascular and muscular system to sustain prolonged effort at low intensity efficiently. It is measured by two indicators: the power or pace you can maintain in Zone 2 (60-75% HRmax) and muscular capillary density (number of capillaries per muscle fibre).

Capillary density increases slowly: it takes 12 to 16 weeks of sustained Zone 2 volume to observe significant improvement. This is why base periods must last at least 3 months, ideally from November to February for a summer race objective.

The classic mistake: going directly from autumn competitions to specific sessions in January without a base phase. The athlete certainly accelerates their anaerobic qualities but remains capped on long distance by an insufficient aerobic engine. Ironman is raced at 80 to 85% of maximum VO2max on the bike, meaning 95% of the work is aerobic.

How to structure an effective base phase

VOLUME BEFORE INTENSITY: during the base phase, 80 to 85% of weekly volume should be run, cycled and swum in Zone 2 (pace at which you can speak in full sentences). The remaining 15 to 20% can include strength work (weights, hills), not lactate intervals.

THE BASE TEST: after 8 weeks of base phase, do a simple test. On a 2h bike ride at constant Zone 2 heart rate (e.g. 130 bpm), measure your average power or speed. If it has increased by 5 to 10% without your HR rising, your aerobic base is improving.

STRENGTH WORK IN BASE PHASE is often underused. 2 weightlifting sessions per week focused on fundamentals (squat, light deadlift, core) improve running and cycling economy, reduce injury risk and maintain muscular strength during high-volume periods.

COMMUNICATE WITH YOUR BODY: chronic fatigue during the base phase is normal. Irritability, insomnia or persistently elevated resting heart rate (more than 5 bpm above your normal) for more than 3 days are signals of too high a load. Reduce volume by 20 to 30% for the week.

The physical principles governing descent safety

Understanding physics allows conscious decisions rather than reactive ones. On a descent, four forces apply simultaneously: gravity (accelerates you), air resistance (slows you down, grows as the square of speed), tyre friction (brakes), and the gyroscopic effect of wheels (directional stability).

THE MAIN SUPPORT POINT: descents are piloted primarily with body weight, not brakes. Dropping the heels (loading the pedals), lowering the shoulders and keeping elbows slightly bent absorb vibrations and maintain stability. A tense athlete (straight arms, high shoulders) is an athlete who vibrates and loses control.

BRAKING: brake BEFORE the corner, never in the corner. In the corner, your only function is to lean and aim at your apex. Braking in a corner causes a fall in 90% of cases because it straightens the bike (and therefore the lean angle) exactly when you need maximum lean.

Progressive learning and limits to respect in competition

TECHNICAL PROGRESSION: start with wide, regular descents (no sharp corners, dry road). Practise the braking-before-corner-apex sequence in loops for 30 minutes on the same descent. A well-known descent is an ideal learning environment.

EQUIPMENT: before working on technique, check your brake pads (at least 2 mm thickness), your tyre pressure (maximum pressure indicated on the tyre sidewall, not necessarily the maximum possible pressure) and that your brakes bite progressively (not all-or-nothing braking).

IN IRONMAN COMPETITION SPECIFICALLY: safety rules vary by race. The basic rule is: descend at your comfort speed, not the theoretically achievable speed. Gaining 2 minutes on a descent by taking a crash risk is not rational on an Ironman where penalties (DQ or DNF through injury) cancel any benefit.

GOLDEN RULE: the ideal descent for an Ironman triathlete is the one where you arrive at the bottom with relaxed forearms and a stable heart rate. If you arrive at the bottom with shaking hands and heart rate at 150 bpm, you over-committed.

Why 180 spm is the reference number

Jack Daniels' landmark 1984 study of elite Olympic runners found that virtually all of them ran between 175 and 185 steps per minute, regardless of distance (from 5 km to marathon). Low cadence (< 160 spm) is associated with longer ground contact, excessive vertical oscillation and increased risk of tibial stress and knee pain.

Reaching 180 spm does not mean running faster: it means taking shorter, more frequent steps. Your speed stays the same, but the braking energy at each footstrike decreases. It's about efficiency, not speed.

How to measure and improve your cadence

MEASUREMENT: most modern GPS watches measure cadence in real time. Otherwise, count your right steps for 30 seconds and multiply by 4. If you get less than 160 spm at easy pace, there's a lever.

IMPROVEMENT: start by targeting +5 spm from your current cadence, not directly 180. Technique: audio metronome (free app on phone) set to target. Run 5 minutes at target cadence, 5 minutes natural, 5 minutes target. After 2 weeks, your brain will have integrated the new rhythm.

CAUTION: don't change cadence AND pace at the same time. Change cadence first at easy pace. Your speed will adapt naturally afterwards.

Cadence on the Ironman marathon

After 180 km of cycling, your natural cadence will drop 5-10 spm. If you've trained your brain to run at 175 spm, you'll drop to 165-170 deep in the marathon: that's still acceptable. If your base cadence is 160, you'll drop to 150: every step is then potentially injurious.

Brick strategy: during your bike-run sessions, always exit the bike with a cadence intention. The first 10 minutes of running off the bike are when cadence is hardest to hold.

Why bilateral breathing changes the race

In open water, waves, current and goggle fog don't only come from one side. If you always breathe to the right, you'll be blind to everything on the left: other swimmers, turn buoys, the swim line. Bilateral breathing (every 3 strokes: left-right-left-right alternating) gives you complete vision and reduces trajectory corrections.

In biomechanical terms, breathing on one side creates asymmetric hip rotation and a tendency to swim in a curve. Swimmers who consistently veer the same way often have one-sided breathing.

The 4-week progression

WEEK 1: warm up in one-sided breathing (your usual side), then 10 x 50 m breathing only on the non-dominant side. Expect to swallow water the first few lengths: that's normal.

WEEK 2: 50% of lengths bilateral (one stroke, two strokes, one stroke: 3-stroke alternation). 50% one-sided.

WEEK 3: 80% bilateral, 20% one-sided. Start swimming bilateral on 200 m sets.

WEEK 4: 100% bilateral in all training except sprints. In racing, you can still use one-sided breathing for sprint phases (start, buoys), but always return to bilateral in calm swimming.

What happens in your body in the heat

In the heat, your heart has to work for two: send blood to muscles AND send blood to the skin to cool. Cardiac output is shared, reducing power available to muscles. In addition, dehydration accelerates: 1% of body weight lost in water = 3-4 extra bpm of heart rate for the same effort.

After 10-14 days of training in hot conditions, your body adapts: increased plasma volume, earlier and more abundant sweating, reduced heart rate at equivalent load. These adaptations persist 2-4 weeks after exposure stops.

The practical acclimatization protocol

SIMPLE METHOD (no sauna required): for 10 days before your competition, do at least one session per day in hot conditions. This means dressing warmer than necessary (light thermal layer), or training at midday if your region is warm.

SESSIONS: 60 to 90 minutes is enough. Intensity should stay moderate (zones 2-3). This is NOT the time for quality sessions: it's controlled thermal stress, not training overload.

HYDRATION DURING ACCLIMATIZATION: drinking salted water (1 g of salt per litre) during hot sessions accelerates plasma expansion. Weigh yourself before and after each session: you should recover your starting weight within 4 hours.

Race day strategies

PRE-COOLING: if possible, take a cold shower 30 minutes before the start. Hold a cold bottle while waiting. Pre-cooling reduces starting core temperature and delays when you reach your critical temperature.

ON THE BIKE: pour water on the back of the neck and forearms at aid stations, not on the head as sunglasses and helmet reduce its effectiveness. Keep a separate water bottle away from your isotonic.

ON THE RUN: walk through aid stations to bring HR down, put ice down your shorts if available (old Kona trick), slow your pace by 10-15 seconds per km if temperature exceeds 30 degrees: better to finish running than leave by ambulance.

Phase 1: aerobic base (20 to 16 weeks before the race)

Single goal: build your aerobic base (VO2max and cardiac capacity). Everything is done in zone 1-2 (< aerobic threshold). No intervals, no speed. Progressive volume: +10% per week maximum, with a recovery week every 3-4 weeks.

Typical mistakes: wanting quality sessions too early ('but I'm bored'), or not respecting the progressive volume ceiling and getting injured at week 6. The aerobic base takes time to build and it doesn't show on short-term times. It shows on race day.

Phase 2: specific preparation (16 to 4 weeks before the race)

Goal: simulate race conditions and develop Ironman-specific qualities (long-duration endurance, power under fatigue, nutritional management). Volume remains high but 1-2 quality sessions per week per discipline are introduced.

Key sessions of this phase: long bike rides (4-6 h, 70-90% of target race pace), long run of 2-3 h, brick sessions (bike followed by run), open-water swim sessions. Intensities stay moderate: never above zone 3 for more than 30 minutes.

Phase 3: taper and sharpening (4 to 0 weeks before the race)

Goal: arrive fresh on race day with sharp fitness. Progressive volume reduction (-30% week 4, -50% week 3, -70% week 2, minimal week 1). Maintain intensity: a few short quality sessions to keep the nervous system alert.

Ironman taper duration: 3-4 weeks for most amateurs (volume > 12 h/week at peak). Lower-volume runners (8-10 h/week at peak) can manage with 2 weeks. Taper is individual: some need 4 weeks, others peak better with 2. Experiment on a half-Ironman before your main objective.

Preparation starts the night before

MENTALLY SET UP YOUR T1 ZONE: visualise each movement in order. From exiting the water to departing on the bike. How many steps? In what order? How long for each?

OPTIMAL T1 SEQUENCE: (1) remove cap and goggles while running to the bike, (2) open the wetsuit while running (pull the zip from the neck down to the waist), (3) arrive at the bike, slide the suit down to the feet, step out, (4) put on helmet, (5) bike glasses, (6) shoes if already clipped in, (7) leave the rack.

SHOES ON THE BIKE: an advanced technique is to fix the shoes on the pedals BEFORE the race and leave in socks, then put on shoes on the first straight. Gain: 20-40 seconds. Requires practice in training.

The mistakes that waste time

MISTAKE 1: stopping to completely remove your wetsuit before reaching the bike. Remove it while walking or running to waist level, finish at the rack.

MISTAKE 2: searching for your bike. Identify your rack during warm-up, count bikes from each end, note a visual landmark (cone, sign, position relative to the central aisle).

MISTAKE 3: leaving without helmet buckled. Penalty or disqualification at major events. A habit to ingrain: helmet BEFORE shoes, always.

MISTAKE 4: too much equipment in T1 zone. Every extra item = extra decision = time lost. Limit yourself to the strict minimum: helmet, glasses, shoes (if not mounted on bike), starting gel if needed.

The perfect T2 sequence

BEFORE ARRIVING IN T2: start unfastening your bike shoes 500m from the transition entrance. Pedal in socks for the last 200m if you used the shoes-on-bike technique. This allows you to jump straight to running after racking the bike.

OPTIMAL T2 SEQUENCE: (1) dismount at the dismount line, never before; (2) run to the rack pushing the bike; (3) hang the bike on the rack; (4) remove the helmet; (5) change shoes; (6) grab the run cap or visor; (7) grab the race number belt if not already worn under the helmet.

RACE NUMBER BELT TIP: wear your race number belt under your cycling kit or stick the number to your TRI-TOP. You eliminate an entire step in T2.

Managing heavy legs for the first kilometres

BIKE LEGS: the first 500m to 1km of running after a long bike ride are always tough. Your body is switching from seated pedalling to upright running. Blood circulation in the quadriceps is different, muscle recruitment changes.

STRATEGY: don't look at your pace for the first 2 kilometres. Run by perceived effort, not by GPS. The feeling of heaviness normally disappears between km 1 and km 3 on a 70.3, between km 2 and km 5 on an Ironman.

DON'T TRY TO MAKE UP LOST TIME: if you had a slightly slow T2, the temptation is to go too fast to compensate. That's the classic mistake that leads to hitting the wall at marathon km 25. Hold your target pace, T2 is already behind you.

Why brick sessions work

THE BIKE LEGS PROBLEM: coming off the bike, the hip flexors and quadriceps are fatigued and congested in a rotary movement pattern. Running requires the opposite linear pattern. This mismatch creates the characteristic 'wooden legs' sensation.

NEUROLOGICAL ADAPTATION: brick sessions allow the central nervous system to learn to rapidly recruit the right muscles in the right order after a cycling effort. This is a neuromuscular adaptation, not purely cardiovascular.

RECOMMENDED FREQUENCY: maximum 1 brick session per week during specific preparation (10-6 weeks before the race). Before that, 1 brick every 2 weeks is enough. Beyond 2 bricks per week, the injury risk exceeds the adaptation benefit.

Types of bricks and their use

SHORT BRICK (adaptation protocol): 60 min cycling at moderate intensity (zone 2-3) + 15-20 min running. Objective: adapt the nervous system. Do until 10 weeks before the competition.

LONG BRICK (race simulation): 2h30-3h cycling (with the last 30 minutes in zone 3-4) + 30-45 min running. Objective: replicate race conditions. Do 8-4 weeks before.

INTENSITY BRICK: 45-60 min cycling with zone 4-5 intervals + 15 min fast running. Objective: work on the transition under neuromuscular fatigue. Reserved for experienced athletes, not to be repeated more than once a month.

FORBIDDEN STACKING: never chain a swim session, a long bike and a run on the same day except for a real race simulation (rare, 1-2 times in the entire preparation).

Overuse syndrome: the triathlete's number 1 injury

DEFINITION: an overuse injury occurs not from a single trauma but from the accumulation of repetitive micro-traumas that the body doesn't have time to repair between sessions.

MOST COMMON INJURIES BY DISCIPLINE:

SWIMMING: swimmer's shoulder (rotator cuff tendinitis), often caused by poor hand entry position or too rapidly increased swim volume. Prevention: shoulder proprioception work, elastic band exercises, middle-finger-first hand entry.

CYCLING: iliotibial band syndrome (IT Band), outer knee. Typically occurs after a long bike ride or rapid volume increase. Prevention: bike fitting (saddle height, knee angles), hip abductor strengthening.

Running injuries and the 10% rule

RUNNING (the most injury-prone triathlon discipline): tibial periostitis (shin splints), plantar fasciitis, Achilles tendinitis, stress fracture (femur or tibia). All are overuse injuries.

THE 10% RULE: never increase your running volume by more than 10% per week. This rule applies to cycling and swimming too. It's the number one cause of injury in triathletes who increase their training load too quickly at the start of the season.

WARNING SIGNS TO NOT IGNORE: pain that starts when warm and disappears when warm (early sign, reduce intensity), pain present on waking (intermediate sign, 48h rest), pain that increases with effort (serious sign, consult immediately).

THE TRIATHLETE'S TRAP: if your knee hurts running, you switch to cycling. If your shoulder hurts swimming, you run more. Result: the primary injury becomes chronic, and you often develop a secondary injury through compensation.

Positioning yourself smartly at the start

THE EXTREMITIES RULE: if your swimming level is below or equal to the average of your wave, position yourself on the sides or at the back. The first 20 metres will be less contested and you can find your rhythm without getting hit.

FOR STRONG SWIMMERS: position yourself on the side corresponding to the first buoy (usually right if the course turns right). Swim diagonally to cut the line instead of swimming directly behind others.

SELF-SEEDED WAVE POSITIONING (WAVA): at large events, waves are organised by predicted swim time. Be honest about your estimate: placing yourself ahead in a fast wave would expose you to violent contact with faster swimmers.

Managing stress and breathlessness

THERMAL SHOCK ON ENTRY: jumping into 18-degree water can trigger a gasping reflex (involuntary and irrepressible inhalation) and hyperventilation. Technique: before the start, splash your neck and forearms with the race water. Enter the water gently if the temperature is below 20 degrees.

EMERGENCY BREATHING TECHNIQUE: if you lose your breathing rhythm at the start of the swim (partial panic), immediately roll onto your back, take 4-5 deep breaths, let a few swimmers pass, then restart crawl slowly. There is no shame. Better to lose 30 seconds than to panic.

NAVIGATION IN TURBID WATER: in a mass of swimmers, lift your head every 6-8 strokes to sight the buoys. Don't just follow the feet of the swimmer in front: in the chaos of a mass start, they may themselves be swimming in the wrong direction.

Mistakes 1 to 3: training

MISTAKE 1: neglecting swimming. Swimming is the discipline where technical improvement has the greatest impact. 1 minute saved over 1900m in swimming represents 2-3 times more preserved energy value than 1 minute saved on the bike or run. Yet beginners often swim once a week (insufficient to improve) and over-invest in cycling or running.

MISTAKE 2: running too fast too often. Beginner triathletes run 80% of their kilometres in zone 3-4 (uncomfortable but not intense). The endurance paradox: running more slowly (zone 1-2) the majority of the time makes you faster in the long run. Test: if you can't hold a normal conversation during your jog, you're going too fast.

MISTAKE 3: not planning recovery weeks. The body doesn't adapt during effort, it adapts during recovery. A recovery week (volume reduced by 30-40%) every 3-4 weeks is not a luxury: it's the condition for your training to produce real adaptations.

Mistakes 4 and 5: racing and logistics

MISTAKE 4: not testing race nutrition in competition. Race nutrition (gels, isotonics, bars) must be tested in training on long rides BEFORE the competition. Race stress and effort accelerate transit. A product that goes down well in easy training can cause abdominal cramps during a 70.3. Rule: nothing new on race day.

MISTAKE 5: underestimating transition logistics. The transition zone is a work area. Arriving 30 minutes early allows you to find your spot, set up your equipment calmly, and visualise your bike exit and run exit route. Arriving at the last minute creates stress that affects concentration and the first cycling kilometres.

The 3 concrete tests of real zone 2

TEST 1 - THE TALK TEST: you must be able to hold a complete conversation in full sentences without catching your breath between words. If you can only say groups of 2-3 words, you're in zone 3. This test is more reliable than HR alone because it measures the actual state of your ventilatory system.

TEST 2 - STABLE HR: in real zone 2, your HR stabilises in 10-15 minutes then stays stable (variation less than 5 bpm). If your HR keeps rising throughout the session (even slowly), you're too high or it's too hot (heat can raise HR by 5-15 bpm autonomously).

TEST 3 - RPE BETWEEN 2 AND 4/10: the effort perception must be 'easy to moderate'. You should finish a 2-hour zone 2 session feeling fresh, with the sense that you could continue for 45 more minutes. If you're breathless at the end of the session, it wasn't in zone 2.

Adjusting your zones in practice

YOUR ZONES MAY BE POORLY CALIBRATED: if you use zones based on an estimated max HR (220 - age), they can be off by 5-15 bpm from your reality. A cycling FTP test or a threshold run test (30 min sustained effort) gives much more precise zones.

CONDITIONS THAT RAISE HR WITHOUT CHANGING EFFORT: heat (30 degrees = HR +10-15 bpm), dehydration (1% dehydration = HR +3-5 bpm), cumulative fatigue, stress, lack of sleep. In hot weather, run at talk test pace and ignore HR - it will always be elevated.

EXPECTED PROGRESS: with 3 months of correctly executed zone 2, your zone 2 pace increases by 15-25% for the same target HR. That's the signal that your aerobic base is improving.

Why bricks work and how the body adapts

THE HEAVY LEGS SYNDROME: in the first 5-10 minutes of the brick run, legs feel like concrete. This is a neuromuscular adaptation: the cycling motor pattern (high frequency rotation, concentric push) must convert to the running motor pattern (stride, eccentric push). This conversion delay is trained and can go from 10 minutes to 2-3 minutes with specific training.

METABOLIC ADAPTATION: on the bike, metabolism works at a different carbohydrate/fat ratio than the marathon. The brick also trains metabolic reconversion. After 8-12 weeks of regular bricks, the bike-to-run transition becomes physically and mentally smoother.

RECOMMENDED QUANTITY: 1 brick per week is sufficient in build and peak periods. In base period, 1 per fortnight is enough. Beyond that, the benefit/fatigue ratio decreases: frequent bricks wear out the legs without incrementing neuromuscular adaptation.

Optimal brick structure depending on the period

BASE BRICK (base period, < 20 weeks from race): 45-90 min stable Z2 cycling + 15-25 min Z2 running. Goal: accustom the body to the change, not create specific fatigue. The run should not be in difficulty.

SPECIFIC BRICK (build/peak period, 8-16 weeks from race): 2-3h cycling with 30-45 min at race pace (Z3-Z4) + 30-45 min run with the last 15 minutes at target Ironman pace. This type of brick specifically targets 70.3 and Ironman performance.

FINAL BRICK (3-4 weeks before race): 1h30-2h race pace cycling + 30 min race pace running. Mental rehearsal as much as physical. Simulate transitions: shoes, starting rhythm, first 500m at target pace.

The often underestimated advantages of solo training

PRECISE INTENSITY CONTROL: in a group, 80% of athletes go too fast on long rides. Social pressure and competitive instinct push individuals above their target zone without realising it. Solo forces you to listen to your body and respect zones.

SCHEDULE FLEXIBILITY: solo allows training at the optimal time for your biology (some athletes have a performance peak at 6am, others at 6pm). Adapting quality sessions to your chronotype can improve performance by 5-10% without changing volume.

MENTAL STRENGTH: the Ironman is an individual event. Learning to manage pain, boredom and doubt in solo during training is a direct transfer to the race. Athletes who only train in groups sometimes struggle to manage the difficult phases of the Ironman when they find themselves alone at marathon km 20.

Group advantages that solo cannot replace

SURPASSING IN QUALITY SESSIONS: for interval sessions, threshold repetitions or VO2max blocks, a group allows going further than you would alone. Collective motivation and positive competition make athletes produce 5-15% more effort. These sessions should be in a group.

LEARNING BY OBSERVATION: riding in a peloton, swimming in a draft, running with faster athletes = permanent technique learning by osmosis. Bike position details, cornering technique or stride are often corrected in groups in ways no virtual coach can achieve.

LONG-TERM MOTIVATION: adherence studies show that athletes who have a training group stay 60% longer in their programme than solo athletes. Social accountability (having someone count on your presence) is the best guarantor of consistency.

The real impact of weight on each discipline

SWIMMING: weight has a NEGATIVE impact on buoyancy and a POSITIVE impact on traction power. In practice, the net impact is almost zero for most amateur triathletes. Technique vastly outweighs mass in the water.

CYCLING: the power-to-weight ratio is the key factor on segments with elevation. On flat terrain, absolute power and aerodynamics dominate. On a flat Ironman (like Barcelona), losing 2 kg theoretically saves 1-2 minutes on the bike - but if this loss impacts power, the gain is cancelled.

RUNNING: the biomechanical impact is the most direct. Each additional kg increases impact forces by approximately 3 times bodyweight at each stride. But losing 1 kg of muscle = losing running power and increasing tendinopathy risk.

The danger of relative energy deficiency (RED-S)

RED-S (Relative Energy Deficiency in Sport): when energy intake doesn't cover training-related expenditure, the body enters survival mode. Direct consequences: loss of muscle mass (the opposite of the desired effect), drop in sex hormones (testosterone/oestrogen), immunosuppression, stress fracture risk, performance decline.

WARNING SIGNALS: persistent fatigue even after recovery weeks, frequent infections, menstrual irregularities in women, low libido in men, performances stagnating or declining despite training, involuntary weight gain or loss.

PRACTICAL RULE: during intensive training periods (build or peak block), don't actively try to lose weight. Body composition improves naturally with training over 6-12 months without caloric restriction. If you want to optimise your weight, do it during base period, never during loading periods.

Why cycling creates a mobility deficit

In the aero position, the hip stays at roughly 45 degrees of flexion for hours. The psoas and rectus femoris adapt to this shortened position. When you switch to running, those muscles can no longer fully extend, reducing stride length and increasing the risk of knee and hip injuries.

Biomechanical studies show a 10-degree hip extension mobility deficit reduces running power by 3-5%. Over a 4-hour marathon, that translates to minutes lost directly linked to cycling position.

The 3 essential exercises

1. LOW LUNGE (hip flexor stretch): back knee on ground, push hips forward, shoulders upright. Hold 60 seconds each side, twice. Do systematically after every bike ride over 90 minutes.

1. LYING PIGEON (figure 4 stretch): lie on your back, right ankle on left knee, pull left toward chest. Progressive over 60 seconds each side. Specifically targets the piriformis and posterior hip capsule.

1. GLUTE BRIDGE: lie on your back, feet flat, push hips toward ceiling and squeeze glutes at top. 3 sets of 15 reps. Activates the glutes that compensate for psoas deficit.

When to do these exercises

After cycling (warm, receptive muscles): low lunge + lying pigeon. Morning or evening independently: glute bridge. NEVER do deep static stretches BEFORE an intense session: risk of muscle micro-laxity. Dynamic warm-up (leg swings, high knees) is more appropriate.

Mistake 1: starting the taper too late

An effective Ironman taper starts 3 weeks before the race, not 2. Week -3: -25% volume, intensity maintained. Week -2: -40% volume. Week -1: -60% volume. Your TSB (Training Stress Balance) should go from -20 (block work) to +10 to +15 on race day.

If you start only 2 weeks out, TSB will still be negative on race day (fatigue > fitness) and you will pay for it on the marathon. Rule: the drop begins 21 days out, never less.

Mistake 2: cutting intensity along with volume

Many athletes cut volume AND intensity together out of caution. Mistake: without stimulus, VO2max drops 2-3% per week starting day 7 with no hard effort. Three weeks without intensity = losing the sharpening.

Protocol: keep 1 short threshold or Z4 session per week during taper (e.g. 3 x 5 min Z4 on the bike, or 4 x 800 m at marathon pace on the run). Volume drops, intensity stays. Your brain keeps the neuromuscular channel active.

Mistake 3: under-fueling during the taper

Falling volume does NOT mean falling calories at the same rate. Hepatic and muscle glycogen synthesis needs 5-6 days to fully saturate before the race. Rule: maintain 90% of week -3 caloric intake, with a bump to 10 g/kg of carbs in the 48 h before the start (i.e. 700 g of carbs for a 70 kg athlete).

If you target a caloric deficit during taper ("lose 1-2 kg before the race"), you will start with incomplete reserves. The weight you lose is water and glycogen: exactly what you need on race day. Eat more carbs in week -1, not less.

The baseline: 60-90 g/h

For a beginner or intermediate IM athlete, 60-90 g/h is the digestive comfort zone. At that level you cover ~80% of gross energy demand (the rest comes from fat stores).

Concrete example for ~75 g/h: 1 bottle of sports drink (40 g) + 1 gel (25 g) + half a banana (10 g) every hour. Run it on the clock, not on hunger.

Why not above 90 g/h by default

Your gut has a max absorption rate (~1 g/min glucose only, ~1.5 g/min with a 2:1 glucose:fructose mix). Above that you pile up in the stomach and end up in a forced pit stop at km 25 of the closing marathon.

Pushing to 100-120 g/h is possible BUT demands 8-12 weeks of "gut training" (sessions with progressive intake). Test on long rides, NEVER on race day.

Mix: not just simple sugars

The 2:1 glucose-to-fructose ratio (maltodextrin + fructose) maximises absorption via two separate gut pathways. Modern sports drinks and gels (Maurten, SiS Beta Fuel, Precision) are calibrated. Avoid solid bars after hour 4 of the bike: digestion becomes a bottleneck.

On the marathon: switch to gels + diluted cola (lower osmolarity, easier to tolerate while running).

Why 3 hours before

Three hours lets your stomach empty (plain water goes faster) AND your liver rebuild its glycogen store (~100 g, your "start" reservoir). Less than 2 h = you start with a full stomach, abdominal cramps in the water guaranteed. More than 5 h = you start partly fasted, hunger returns by km 30 on the bike.

If gun is 7am: breakfast 4-4:30am. If gun is 6am: shift toward a heavier dinner the night before + a small snack 90 min before the start.

The target: 1.5-2 g carbs/kg, low fibre, low fat

For a 70 kg athlete: 105-140 g of carbs. Fibre (whole grains, fruit with skin, vegetables) accelerates transit = bathroom run during the swim. Fat (butter, cheese, eggs) slows gastric emptying = heaviness. Stick to digestible refined carbs: white bread, honey, ripe banana, rice, cooked oats.

Fluids: 500-700 ml of light drink (coffee OK if habitual, flavoured water OR diluted sport drink).

Three tested breakfasts

Option A : European classic: 100 g oats cooked in water + 1 ripe banana + 2 tbsp honey + 1 tbsp jam (~135 g carbs).

Option B : bread & honey: 4 slices white bread + honey + 1 tsp smooth almond butter (sparingly) + 1 banana (~120 g carbs).

Option C : savoury rice (sensitive stomach): 150 g cooked white rice + 1 tbsp jam on the side + 1 fruit juice 50/50 diluted (~110 g carbs).

Absolute rule: eat THIS exact breakfast on your last 2 long sessions to confirm your stomach is OK with it.

The framework: 60-90 g carbs/h

You already have the global target: 60-90 g carbs per hour (see the "Ironman Nutrition" tip). Over 5-6 h biking, that means stockpiling 360-540 g of exploitable carbs, from rear pockets or aid stations.

The glucose+fructose MIX target (1:0.8 or 2:1 ratio) holds. Beyond 60 g/h pure glucose, your gut saturates.

The question is: HOW do you deliver 360-540 g without wrecking your stomach? That's where solid vs liquid comes in.

Liquid: fast, but limits

For: ultra-fast digestion (15-20 min absorption), simple, packs hydration + electrolytes + carbs in one vector. Just drink.

Against: satiety hits fast. Drinking sugary sports drink for 6 h triggers nausea in 50% of athletes after h 3-4. The sweet taste becomes unbearable.

Realistic target: 250-400 ml/h of sports drink (at 60-80 g carbs/L) → 15-32 g carbs/h from drinks alone. You need to top up.

Tools: homemade bottles with maltodextrin + fructose powder (Tailwind, SiS Beta Fuel, Maurten Drink Mix 320, or DIY). Allows 90 g/h in liquid alone IF you accept 600-700 ml/h, which is digestive limit territory.

Solid: volume, but demanding digestion

For: chewing = hormonal and psychological satiety signal. Breaks sweet monotony. Often brings salt, fat, protein.

Against: slower digestion (30-60 min). Beyond 2 bars/h, the stomach protests. Biking in aero = abdominal compression, the stomach hates this EVEN more.

Realistic target: 1 energy bar every 60-90 min (30-40 g carbs). Plus dried fruit (dates, apricots → 15-25 g carbs), chips/crackers (salt that cuts the sweet), white-bread-honey sandwich early-IM if you're very tolerant.

Golden rule: test EVERYTHING in training, especially in aero. The Nutella sandwich that works on an easy run does NOT work on a 4 h TT-bar effort in a pack.

The mix that works for 80% of athletes

On an Ironman 5-6 h bike, a stable template:

• Phase 1 (h 0 → h 2): 60-70% solid (stomach is open). Bars + dates. Sports drink as backup.
• Phase 2 (h 2 → h 4): 50% solid / 50% liquid. Sugar fatigue is starting → swap every other bar for a gel (more concentrated, less volume).
• Phase 3 (h 4 → end): 80% liquid + gels + 1-2 salt chips/crackers. No more heavy bars. Prep T2 with a near-empty stomach.

Test this protocol on 3 long bricks BEFORE the race. If you puke in training, you've won : you know you HAVE to adjust. If you puke on IM day, the race is over.

What fasted training does (and doesn't)

Doing a morning session without eating = forcing your body to mobilise fat (lipolysis) instead of glycogen, which is low after an overnight fast.

What it's supposed to deliver: better "metabolic flexibility" → your body becomes more efficient at burning fat at moderate intensity (Z1-Z2). Theoretically useful in IM where 50-60% of energy comes from fat over 6-10 h.

What it does NOT do: improve your VO2max, threshold power, or speed. "Performance" adaptations require training with carbs available. Fasted NEVER replaces a properly fuelled intense session.

Key studies: Stannard 2010 + Van Proeyen 2010 show a 5-10% gain in lipid oxidation after 6 weeks of fasted Z2. But no improvement in final long-race performance. Unless you also include carbs during your intense sessions.

The protocol that works: 2 sessions/wk max, Z1-Z2 only

If you want to try, here's the literature-validated (and lowest-risk) version:

• Max 2 fasted sessions/week, never back-to-back.
• 60-90 min max duration, never 2 h+. Beyond that, you enter muscle catabolic mode (lean mass loss).
• Strictly Z1-Z2 intensity (RPE 3-4/10, fluent conversation). No intensity, no intervals.
• Black coffee + water OK on waking. Sugar/juice = ends the fast.
• Eat a carb-based solid meal within 30 min after. Otherwise you defuse the adaptations.

Avoid entirely: if you do 14 h+/week, during a heavy load block (3 weeks hard), returning from injury, during taper.

The real risks (often understated)

Risk #1: rebound hypoglycaemia. Push past Z2 fasted and you can crash (blurred vision, shakes, cold sweats). Real risk on the bike in a pack or in the mountains. 30% of fasted-trainers report at least 1 episode/year.

Risk #2: chronic under-recovery. Fast 3-4 times/wk and sleep degrades, mood drops, menstrual cycles disturb in women (documented sport-induced amenorrhea).

Risk #3: lean mass loss. Cumulated over 8-12 wk in athletes < 65 kg, 1-2 kg muscle loss observed. Catastrophic for an IM where power/weight and the ability to run 42 km matter.

If you fast, track: weekly weight (alert if > 1% drop in 2 wk), sleep (alert if degradation), HRV (alert if sustained drop). If anything drifts, stop fasted for 3-4 weeks.

Who actually gets a positive ROI

Positive ROI:

• IM athletes in "base" phase (12-16 wk pre-race), moderate 8-12 h/wk volume.
• Athletes used to 4-5 meals/day who want to reduce sugar dependence.
• "Endomorph" body type athletes with comfortable fat stores (BMI > 21).

Negative ROI (avoid):

• Athletes < 65 kg, female athletes with already-disturbed cycle, growing adolescents/young adults.
• Athletes in peak volume (>14 h/wk) or peak intensity (3+ Z3 sessions/wk).
• Type-1 diabetics or pre-diabetics.

Verdict: useful as an occasional tool for an intermediate athlete in base, never a permanent strategy. No IM pro does fasted in peak. They know what works.

Gels: maximum absorption speed, tolerance to verify

A standard energy gel contains 20-25 g of carbohydrates as maltodextrin + fructose (sometimes pure glucose). Its semi-liquid texture allows rapid gastric emptying : carbohydrates reach the blood in 10-20 min after ingestion with enough water.

Advantages: easy to carry and take without slowing down, calibrated formats (you know exactly how many carbs you're taking), readily available at Ironman aid stations.

Disadvantages: variable digestive tolerance. Concentrated gels without sufficient water cause GI issues in 30-50% of triathletes in competition (Jeukendrup 2011). Key: ALWAYS take a gel with 150-250 ml of water : never with a sports drink (osmolality too high → possible diarrhea). Never test new gels in a race.

When: late bike phase (km 80-180) and the ENTIRE IM marathon. At high intensity, the stomach shuts for solids : gels go down when bars don't. Recommended frequency: 1 gel every 20-25 min on the run with water at the same aid station.

Bars: sustained energy, for the bike only

A standard energy bar (RiceWave, Clif Bar, homemade rice cake) contains 30-50 g of carbs + fats + proteins (varying proportions). Digestion is slower : 60-90 min for complete emptying. That's a feature, not a bug, for the first half of the bike.

Advantages: longer satiety, palatability (taste and texture are often more enjoyable than gels over long duration), ease of homemade prep (Lionel Sanders homemade rice cakes = 45 g carbs, cost €0.15).

Disadvantages: obviously impossible to take while swimming. Hard to consume at high intensity (km 90-180 on the flat at 90% IF) : chewing and swallowing at high power increases nausea risk. Less precise calibration homemade.

When: the first 90 km of the IM bike (moderately intensive phase). Practical rule: switch to gels + drink in the last 2 hours of the bike and all of the run. Never take a bar after km 100 on a full IM if going above 75% FTP.

Alternative format : waffles (stroopwafels): same category (solid, fast-digesting, ~16g carbs per waffle), popular in cycling (Van der Poel/Pogačar in races). Easy to eat at high bike cadence, better palatability than compressed bars.

Sports drink: hydration + carbs, the underrated tool

A standard isotonic drink (6-8% carbohydrates, 400-600 mg/L sodium) combines hydration and carbohydrate intake. It delivers 30-45 g of carbs per hour at normal volume (500-750 ml/h).

Advantages: no grasping or chewing effort : ideal during the swim (impossible) and on aero bars. Concurrent sodium intake with hydration. Fewer nausea episodes than concentrated high-osmolality gels.

Disadvantages: taste fatigue after 4-6 h (risk of "flavor fatigue" = reduced intake precisely when it's most needed). Weight in the bottle (750 ml bottle = 750 g). Less precise carb control absorbed if sweating forces drinking more than planned.

When: throughout the bike as the hydration base (drink + bar/gel = optimal combination). On the run: use aid station drinks (Coca-Cola late in the race = 10.5g carbs/100ml + high palatability when gel flavor fatigue hits).

The 3-source rule: the best IM triathletes combine all 3 forms sequentially based on intensity and flavor fatigue: bars/cakes (0-90 km bike) + isotonic drink throughout + gels (90-180 km bike, then run). On the run, solid carbs become optional if intensity is high : gels + water + Coca at the end is enough.

The fundamental rule: test in training, not in the race

Any nutritional strategy must be repeated at least 3-4 times in race-like conditions before being used in competition. The digestive system adapts to high-intensity nutrition : it's not innate, it's trained.

Test protocol: during your long bricks (3-4h bike + 1-1h30 run), test exactly the gel/bar/drink ratio you'll use in the race. Note what causes issues (nausea, GI cramps, diarrhea) and what goes down well. Adapt at least 4 weeks before the race.

Target volume for an Ironman: aim for 60-80 g of carbs/h on the bike and 40-60 g/h on the run (intestinal absorption decreases at high intensity). Beyond 80 g/h, only a glucose + fructose mix (2:1) can exceed saturation of a single intestinal transporter (SGLT1 for glucose). "2:1" gels (maltodextrin + fructose) are designed for this.

Hydration cost: each gram of glycogen retains ~3 g of intramuscular water. An Ironman burns 400-600 g of glycogen → releases 1.2-1.8 L of endogenous metabolic water. In practice: don't over-drink thinking you're "compensating for glycogen". Drinking to thirst + urine color control (pale yellow = good) is more reliable than a fixed volume protocol.

Why carb loading works (and when it doesn't)

Muscles store glycogen : the usable form of glucose during exercise. In long-distance endurance, normal reserves (~400-500 g total glycogen) deplete in 90 min to 2h30 depending on intensity. Carb loading aims to push that limit by saturating muscle stores before the start.

What the science shows: a properly executed carb load increases glycogen stores by 20-40 % above normal levels (Burke et al., 2011). On an Ironman, this can delay the 'wall' by 30-60 minutes.

When carb loading doesn't help:

• Events < 75 min: normal stores are more than sufficient : no need to overload.
• Protocol too short (< 36h): not enough time to saturate muscle stores.
• Insufficient intake (< 8 g/kg/day): volume eats the carbs before muscles can store them.
• Training maintained during the loading phase: muscles burn what you're trying to store.

The practical protocol: 72 h out to race morning

J-3 (72 h out): light depletion + load reduction

• Cut training volume to 20-30 % of normal (depletion comes from reduced consumption, not extra effort).
• Keep carbohydrate intake normal (5-6 g/kg/day) : don't overload yet.
• Hydrate well: glycogen binds ~3 g of water per g stored. You'll gain 1-2 kg of water mass : that's normal.

J-2 and J-1 (48-24 h out): loading phase

• Goal: 10-12 g of carbohydrates per kg of body weight per day. For 70 kg = 700-840 g of carbs/day. That's a lot.
• Preferred sources: rice, well-cooked pasta, white bread, potatoes, ripe bananas, applesauce, fruit juice. Low-fibre = lower GI risk.
• Avoid: legumes, broccoli, cabbage, excess raw vegetables (fermentation and bloating).
• Spread across 5-6 meals to avoid overwhelming the digestive system at once.
• Protein: maintain 1-1.5 g/kg/day (keep it, don't overdo).
• Fat: reduce slightly to make caloric room for carbs.

Race morning (J-0)

• 3-4 h before the gun: pre-race meal 1-2 g/kg carbs (e.g. 80 g oat flakes + 1 banana for 70 kg). Easy to digest.
• Avoid any new food or GI-risk item. Test your pre-race meal in training multiple times before race day.

Classic mistakes that sabotage the load

Mistake #1: too much fibre Whole-wheat pasta, whole-grain bread, raw vegetables : excellent the rest of the year, counterproductive during carb loading. Fibre slows absorption and creates digestive load. Switch to white rice, well-cooked white pasta, white bread, applesauce.

Mistake #2: forgetting liquids Recovery drinks, fruit juices, isotonic sports drinks all count toward your carb total : and contribute to hydration simultaneously. Of 700-840 g/day carbs, 100-150 g can come from liquids.

Mistake #3: confusing 'eat more' with 'carb load' The classic error: maintain normal protein + fat + add carbs on top. Result: 1,000+ kcal/day surplus and digestive discomfort. You need to SHIFT calories toward carbs, not just add them.

Mistake #4: trying a new food J-1 or race morning isn't the time to try a new gel, new recovery drink or unfamiliar restaurant dish. Any new GI-risk food must be eliminated in the 48 h before the race.

Mistake #5: neglecting sodium Glycogen retains water : and that water is hypotonic (low in salt). Maintain normal sodium intake during loading to avoid excessively diluting electrolytes. A slight increase in dietary salt on J-2/J-1 is acceptable.

How much water per hour?

Recommendations vary with individual sweat rate, temperature and intensity. But the consensus range is:

0.5 to 1 L/hour in temperate conditions (15-22 °C) for effort at 70-80% VO2max.

Up to 1.5 L/hour in hot and humid conditions (>25 °C, >70% humidity).

The big mistakes:

• Drinking 'to thirst' only (works for effort <2h; insufficient in an Ironman where thirst sensation is blunted by endorphins and distraction)
• Drinking at every aid station without counting (risk of overhydration if aid stations are frequent)

Practical protocol: set a 15-min alarm on your watch during bike and run. 150-200 mL at each beep. Adjust for heat, but the structure gives a regular rhythm without thinking about it.

Sodium: the key electrolyte in long-distance

Sweat contains electrolytes : primarily sodium (Na⁺). Athletes can lose 500 to 2000 mg of sodium per hour in hot conditions.

Risk #1: exercise-associated hyponatraemia Consuming large amounts of plain water without sodium replacement dilutes blood sodium. Below 135 mEq/L (hyponatraemia), symptoms include: cramps, confusion, headache, nausea : and in severe cases (<125 mEq/L), seizures and coma. Hyponatraemia is THE #1 preventable cause of death at major endurance events.

Sodium needs in racing: 500 to 1000 mg/hour (source: American College of Sports Medicine).

Practical sources in Ironman racing:

• Isotonic sports drink (gels + water): ~200-400 mg/L depending on brand
• Salt tablets (e.g. Precision Fuel & Hydration S30/S1000): precise dosing
• Vegetable broth at run aid stations: ~400-600 mg/200 mL
• Pretzels (if available): high sodium density but variable digestion

Basic rule: from 3h of effort onward, add an explicit sodium source at every aid station. Don't rely on energy gels alone unless the label specifies >100 mg Na/gel.

Test in training, not for the first time in racing

Every athlete has a different sweat rate. Some 'salt heavily' (white traces on skin post-exercise), others barely at all. The only way to know your sodium profile is to test:

Simple home test:

1. Weigh yourself naked before a 2h long session without fuelling (drink normally, no compensation).
2. Weigh yourself naked afterwards.
3. Weight difference × 1000 = mL of sweat lost (1 kg ≈ 1 L of sweat).
4. Divide by 2 (duration) = sweat rate per hour.
5. If your clothes are covered in white traces, you're a 'high sodium sweater' and your salt needs are in the upper range.

What to test in brick or long sessions: your complete gel + water + salt strategy, never discovering it for the first time in a race. Better to have 5 bricks with the same protocol than a paper-perfect strategy never tested.

What caffeine actually does during long-distance effort

Caffeine acts primarily on the central nervous system by blocking adenosine receptors : the molecule that creates the sensation of fatigue. In practice:

Proven endurance effects (meta-analyses Doherty & Smith 2005, Grgic et al. 2020):

• Reduction in perceived effort (RPE) of 5-8% at iso-power
• Improvement in time to exhaustion of 11-12% on average
• Better mental alertness (crucial over 7-12 hours of an Ironman)
• Slight improvement in fat metabolism (modest but real contribution)

Effects not reliably confirmed:

• Glycogen sparing (metabolic response is individual, not systematic)
• Improvement in maximum strength (more specific to short efforts)

Important: individual tolerance varies enormously. Approximately 20-25% of people are 'non-responders' to caffeine on performance : often linked to variants of the CYP1A2 gene that controls metabolism. If caffeine has never helped you in training, it won't work miracles on race day.

Timing and dosage: the Ironman protocol

Effective dosage: 3 to 6 mg per kg body weight (mg/kg). For 70 kg: 210-420 mg. Above 6 mg/kg, negative effects (trembling, anxiety, GI issues) outweigh benefits.

Onset time: caffeine reaches peak plasma levels in 45-60 minutes after ingestion. Half-life is 5-6 hours (variable by CYP1A2 genotype).

Recommended strategy for Ironman (race ~10-14 h):

Before the start

• 60 min before start: 200 mg caffeine (gel or tablet, not coffee : uncontrolled dose). Places you at peak at the start of the bike.

On the bike (critical segment, ~5-7h)

• H+3: 100-150 mg (caffeinated gel or tablet) to maintain levels
• H+5: additional 100 mg if the segment is still long

On the run (final marathon)

• H+0 run (marathon start): 100-150 mg : critical moment for alertness and pain management
• H+2 run (km 25-30): final 100 mg if sensations are dropping (watch for nausea if stomach is stressed)

Typical total: 500-700 mg over 10-13h of racing, or ~7-10 mg/kg for 70 kg. Exceeds the 6 mg/kg threshold, but spread over 10h+ : progressive degradation tempers the effective peak.

Preferred forms: caffeinated gels with known doses (e.g. 100 mg/gel) or caffeine tablets. Avoid coffee during racing (unpredictable dose, gastric acidity, variable diuresis).

Classic mistakes and contraindications

Mistake #1: not testing in training The Ironman is NOT the time to discover your caffeine tolerance. Test the protocol (dose + timing + form) on 2-3 long bike sessions or long bricks. Observe: GI issues? Trembling? Abnormal HR increase? Adjust dosage accordingly.

Mistake #2: caffeine instead of hydration Caffeine is mildly diuretic (moderate effect, often overstated : one cup of coffee = net positive hydration, but at high doses in hot conditions = monitor closely). Don't reduce fluid intake by relying solely on caffeine for alertness.

Mistake #3: stopping caffeine before the race 'Detraining' caffeine (stopping 5-7 days before) to amplify the effect on race day is an outdated strategy, unreliable and a source of headaches and irritability the pre-race week. Recent data (Clarke et al. 2019) shows the ergogenic effect doesn't differ significantly between habitual and non-habitual consumers at controlled doses. Continue your normal consumption, simply optimise the timing on race day.

Mistake #4: mixing caffeine with the wrong gel Some caffeinated gels also contain complex sugars that are hard to digest. If you've already had GI problems with gels, check the composition (avoid sorbitol + caffeine simultaneously : double osmotic stress on the intestine).

Contraindications to flag: cardiac arrhythmias, severe anxiety, extreme sleep disorders (if pre-race night is already compromised, caffeine should be dosed carefully).

How much protein per day?

Current recommendations for endurance athletes converge between 1.6 and 2.2 g of protein per kg of body weight per day (Phillips & Van Loon, 2011; Burke et al., 2019). A 75 kg triathlete should therefore aim for 120–165 g/day.

The lower end (1.6 g/kg) is sufficient in base phase with moderate volume. During competition phase, caloric restriction (weight loss), or within 48 h of a long effort, moving up to 2.0–2.2 g/kg optimises muscle retention.

Official RDAs for the general population (0.8 g/kg) are calculated to prevent deficiency, not to optimise sports performance. Don't rely on them.

Timing: the post-exercise window

The post-exercise 'anabolic window' is real, but wider than once thought: 0 to 2 h after exercise. The goal is to ingest 20–40 g of high biological value protein within this window (Trommelen et al., 2019).

In practice after a long session:

• Session < 1 h: 20 g is enough (2 eggs + 150 g skyr)
• Session 1–2 h: aim for 30 g (150 g chicken + low-fat quark)
• Session > 3 h (brick, long ride): 35–40 g + carbs (combined recovery)

Eating nothing within 2 h of a long session is the real enemy of recovery. This common reflex (loss of appetite, fatigue) delays muscle rebuilding.

Nighttime protein: casein

During sleep, your body repairs muscle fibres damaged during training. A dose of 30–40 g slow-digesting protein (casein) before bed extends overnight protein synthesis over 6–8 h (Res et al., 2012).

Practical source: full-fat quark (20 g/100 g), cottage cheese, or thick Greek yogurt. Micellar casein powder works too, but isn't essential if your diet is varied.

This strategy is particularly useful after hard training blocks (high-load weeks, training camps) and during competition phases.

What doesn't work: low-fat fromage blanc at 7 g/100 g. The protein content is too low to trigger synthesis.

Protein sources for vegetarian/flexitarian athletes

The biological value of plant proteins is generally lower than animal proteins (less complete essential amino acid profile). To compensate:

• Combine legumes + cereals (rice + lentils, wholegrain bread + hummus): complete amino acid profile
• Increase total intake slightly: aim for 2.0–2.2 g/kg instead of 1.6 g/kg
• Prioritise: firm tofu, tempeh, edamame, red lentils, protein oats, pea/rice protein powder (if needed)
• Watch leucine: the trigger amino acid for synthesis (abundant in whey, less so in plants) : a dose of 2.5–3 g leucine per protein meal is optimal

Why digestion degrades on the run

The bike-to-run combination subjects the digestive system to several cumulative stresses:

On the bike (5–7h): the aerodynamic position compresses the abdomen, slowing transit. Heat redirects blood flow to muscles and skin (thermoregulation), reducing intestinal supply. Road vibrations create micro-trauma to the intestines.

On the run: running impacts amplify mechanical stress on the intestines (frequent 'gurgling' sounds in late-race triathletes). Low insulin levels and elevated cortisol slow gastric emptying. Vomiting and diarrhoea are 4–6 times more common in the Ironman run than in a standard marathon.

The practical consequence: complex solid foods (bars, sandwiches) often become indigestible after bike km 20. Concentrated gels cause nausea. What went down easily in training may not go down at all on race day marathon.

What still works: late-race nutrition options

In order of decreasing digestive tolerance on the Ironman run:

1. Water + salt: the base. Most athletes can still swallow plain water and salt tablets (Na+, Mg²⁺). Salt maintains plasma osmolarity and reduces cramping. Take at every aid station.

2. Coca-Cola or sweet carbonated drink: one of the oldest finds in long-distance triathlon. Sugar (sucrose) at low concentration, combined with carbon dioxide, stimulates gastric emptying and gives a rapid glycaemic spike. Caffeine provides a cognitive boost. Most Ironman aid stations offer it after km 20–25 of the run. Dose: 1 cup (150–200 ml) every 2–3 aid stations.

3. Warm chicken broth: offered at several major Ironmans (Kona, Frankfurt, Zurich). Hydration + sodium + glutamine without osmotic stress. Very well tolerated even late in the race. Ideal if gels and sweet drinks are causing nausea.

4. Orange or banana quarters: simple carbs, low osmolarity, high tolerance. Orange also provides potassium and vitamin C. Prefer small, well-ripened pieces.

5. Diluted gels: if standard gels (70–100 kcal, 60–80 ml) cause nausea, taking them with 250–400 ml of water instead of 100–150 ml reduces gastric osmolarity and nausea risk. Avoid mixing gel + isotonic drink (double osmotic load).

What WORSENS things: high-fructose concentration gels (>1:1 glucose:fructose) after 6h+ of racing : fructose uses a separate transport mechanism (GLUT5) and saturates faster; bars with fibre or fat (transit already slowed); high-concentration isotonic drinks if the stomach is already distended.

Building your run nutrition plan in advance

Ironman run nutrition is prepared before the race, not improvised on the course.

1. Know the official aid stations: the event website publishes each aid station's content. Check: water, isotonic, cola, broth, oranges, bananas, specific gels. The gel brand provided may differ from what you use in training : bring your own if needed.

2. Simulate on long bricks: practise eating during 3h+ bricks (long bike + 45 min run) under realistic fatigue. The digestive system trains like muscles.

3. Test cola and broth: if you've never tried them in training, don't test them for the first time in a race. Integrate them into 1–2 bricks or long sessions in late preparation.

4. Progressively space out gels on the run: carbohydrate needs on the run (50–60 g/h) are slightly lower than on the bike (60–80 g/h). Space gels further apart (every 40–50 min vs 30–35 min on the bike) to let the digestive system recover.

What caffeine actually does

Caffeine blocks adenosine receptors : the molecule responsible for the sensation of fatigue. The result: it delays perceived effort, improves alertness and can enhance fat mobilization : useful over an 8-17 hour effort.

Lab-measured effect: 2-4% improvement on endurance performance (meta-analysis, Journal of the International Society of Sports Nutrition, 2021). On a 10-hour Ironman, that's 12-24 minutes : not negligible.

Effective dose: 3-6 mg/kg bodyweight. For 70 kg: 210-420 mg. A standard caffeinated gel contains 25-50 mg; a race drink 75-150 mg depending on brand.

Timing: the 60-minute rule

Peak plasma caffeine is reached 45-90 minutes after ingestion. For an IM, two strategies work:

Classic strategy: single pre-race dose, 60 min before the start (coffee or tablet). Advantage: no in-race management. Disadvantage: levels drop mid-race.

Fractionated strategy (more effective over Ironman distance): moderate pre-race dose (1-2 mg/kg), then split intakes via caffeinated gels on the bike (km 60-90) and early in the marathon (km 5-15). Maintains levels throughout.

What not to do: take your first dose of caffeine on race day if you don't consume caffeine during training. Tolerance builds over weeks.

The traps: caffeine doesn't replace sleep or nutrition

In an Ironman, athletes who use caffeine as a 'patch' in the late marathon (because they're exhausted) confuse masking effect with real performance. Caffeine masks fatigue : it doesn't eliminate it. An athlete who is poorly nourished or under-slept and takes a high dose late in the marathon risks drawing on already-empty reserves and underestimating physical degradation.

Other precautions:

• Gastrointestinal effects of caffeine (accelerated transit) are amplified during exercise. Test obligatorily in training before race day.
• People sensitive to caffeine (tremors, palpitations, anxiety) should stay in the low range (1-2 mg/kg).
• Avoid abrupt caffeine withdrawal in the week before the race if you're a regular consumer: withdrawal (headache, fatigue) can last 1-3 days.

The goal: saturate muscle glycogen

An Ironman lasts 8 to 17 hours. Glycogen stores (fast energy) total about 500 g of carbs in a well-trained athlete : roughly 2,000 kcal. That's not enough to cover the whole race : in-race fueling takes over : but starting with full stores is essential.

Race-eve protocol:

• Carb-rich dinner with moderate-low glycemic index (rice, pasta, bread, boiled potato). Target 8-10 g carbs per kg bodyweight in the 24 h before race start.
• Light protein (grilled chicken, eggs, cottage cheese) to avoid overnight hunger without burdening digestion.
• Minimal fiber: no raw vegetables, green salad, legumes. Same for excess fat (fried food, heavy sauces).
• Salt: add salt to your meals (an extra pinch), especially if the race is hot. It helps water retention.

What to absolutely avoid

Classic race-eve mistakes:

• Restaurant feast with exotic or spicy cuisine → major GI distress risk at the start.
• Experimenting with a food or supplement never tested in training → golden rule: nothing new on race day AND the eve.
• Drinking alcohol (even a beer): alcohol disrupts sleep, dehydrates, and impairs muscle recovery.
• Skipping a meal out of nervousness → glycogen stores deplete even at rest (the liver burns ~10 g/h of carbs to maintain blood sugar).
• Overeating to the point of discomfort → overnight GI distress, poor sleep, heavy start.

What's underestimated: hydration the night before matters as much as food. Aim for 500-750 mL of water per hour in the 4-6 h before bedtime (straw-yellow urine = well hydrated).

Sample race-eve menu

Lunch (race eve, 12-1 pm): white pasta or rice + grilled chicken or tuna + one slice of bread + water with a pinch of salt. Optional: ripe banana.

Snack (3-4 pm): white bread + jam or honey + ripe banana (avoid seeded or peeled fruit).

Dinner (6-7 pm max): white rice or boiled potato + roast chicken or eggs + salted broth or light soup. Dessert: plain yogurt + honey. No heavy sauces, no strong cheese.

Before bed: glass of water + optionally a slice of bread with honey if hunger returns at night.

This is not the most exciting menu : and that's exactly the point.

Why cycling is the primary feeding window in an Ironman

Digestive blood flow is less compromised cycling than running (the vibration impacts and postural constraints of running reduce splanchnic blood flow). You can absorb 60-90 g carbohydrates/hour on the bike vs 40-60 g/h while running without triggering digestive distress in most trained athletes.

Furthermore, muscle and liver glycogen stores (approximately 400-500 g total) deplete in 90-120 min of moderate-high intensity effort. An Ironman lasts 8-16 h. Without continuous fuelling on the bike, you arrive at the marathon with an energy deficit that precipitates the wall.

Carbohydrate targets and recommended sources

Targets by duration:

• Under 2 h (sprint/olympic): 30-60 g/h, simple carbs, gels or bars.
• 2-4 h (70.3): 60-75 g/h. Glucose + fructose mix (2:1 ratio) needed from 60 g/h to saturate two intestinal transporters (SGLT1 + GLUT5) and prevent incomplete digestion.
• 4-8 h (Ironman): 75-90 g/h. 2:1 (glucose:fructose) mix essential. Some elite athletes reach 100-120 g/h after progressive gut training.

Practical sources:

• Gels: easy to carry, formats 20-25 g carbs/gel. Prefer isotonic (no additional water needed). Alternate flavours to limit taste fatigue.
• Chews/blocks (SiS Go, Clif Bloks, Spring Energy): good for the first 3-4 hours, not recommended when heat > 28°C (solid digestion slows).
• Homemade carb drink: maltodextrin + fructose (2:1 weight ratio), easy to dissolve, cost-effective. 500-700 kcal in a 750 ml bottle.
• Bananas at official feed zones: OK as a supplement, but impossible to dose precisely.

Common mistakes and how to avoid them

Eating too late: waiting for hunger to eat = blood sugar in free fall. Start eating within the first 20 minutes of the bike (before liver stores decline). A timer every 20-25 min helps maintain regularity.

Eating too little early then catching up: high-dose catch-up triggers intestinal hyperosmolarity (too many concentrated carbs = water pulled into the gut = bloating, nausea, diarrhoea). Better to maintain 60 g/h consistently than try 120 g/h catch-up.

Mixing too many different sources: gels + carb drinks + sweet bars = hard to know the precise dose ingested and stay within the tolerance zone. Simplify: 1 isotonic drink + 1 gel source is enough.

Neglecting sodium: hydric dilution (drinking lots of plain water without sodium) combined with massive carb ingestion can lower natraemia (exercise-induced hyponatraemia). Always include sodium (500 mg/h minimum, 750-1,000 mg/h in heat).

Gut training: if targeting 80-90 g/h, train at this dose during long training rides (4 months before the race). The gut adapts progressively, improving GLUT5 transporter expression. Testing a dose on race day that you have never ingested in training = maximum risk.

Isotonic, hypotonic, hypertonic: what is the difference?

A solution's tonicity corresponds to its solute concentration (sugars + electrolytes) relative to blood plasma (osmolality ~285-295 mOsm/kg).

• Hypotonic (< 285 mOsm/kg): more dilute than plasma. Rapid intestinal absorption. Ideal for pure rehydration (excessive sweating, extreme heat). Examples: plain water, water + pinch of salt, very lightly sweetened drinks (< 4 g/100 ml).

• Isotonic (285-305 mOsm/kg): same concentration as plasma. Rapid absorption + moderate energy supply. Ideal for efforts > 90 min in normal to hot conditions. Typical concentration: 6-8 g carbohydrates/100 ml + 500-700 mg sodium/L. Most commercial sports drinks (Maurten 160, SiS Go, High5 Electrolyte) are isotonic or slightly hypotonic.

• Hypertonic (> 305 mOsm/kg): more concentrated than plasma. Slower absorption, high caloric supply. Used for post-effort energy fuelling or carb loading, NOT for in-race rehydration (can worsen dehydration by pulling water into the gut). Examples: Maurten 320, plain cola.

Hydration strategy by duration and heat

Effort < 60 min: plain water is sufficient in most temperate conditions.

Effort 60-90 min: 400-600 ml/h of water or a lightly sweetened drink. No need for a full isotonic if the pre-effort meal was appropriate.

Effort 90 min to 3 h (70.3): 500-700 ml/h isotonic drink (6-7 g/100 ml + sodium). Target 500-700 mg sodium/h to compensate average sweat losses.

Effort > 4-5 h (Ironman):

• Bike: isotonic drink 6-7% + sodium 700-1,000 mg/h (based on heat), 500-800 ml/h. If using separate gels, switch to a light hypotonic drink (water + electrolytes, no sugar) to avoid carb overload.
• Run: plain water + salt tablets at feed zones + cola in the last 15 km (caffeine + fast carbs).

Dehydration signs to watch: dark urine before the start, intense thirst (already too late), HR > 10 bpm above normal at constant intensity.

Exercise-induced hyponatraemia (real danger): drinking too much plain water without sodium on an Ironman can dilute natraemia below 135 mmol/L, causing nausea, confusion, or even seizures in severe cases. Women, slow athletes and those drinking at every feed zone without managing sodium are at risk. Always pair water with sodium.

Race-day hydration protocol

Evening before the race:

• Pale straw-coloured urine = well hydrated. Reaching this state the night before avoids over-hydrating in the morning (which dilutes sodium).
• 2-2.5 L of water through the day (slightly more than usual).

Race morning:

• 500-700 ml water or light drink in the 2-3 h before the start (last glass 60-90 min before).
• Do not drink litres just before: over-hydration = early hyponatraemia + need to urinate while swimming.

During the race:

• T1: drink 150-200 ml before getting on the bike if hot.
• Bike: execute your plan (timer, bottles, salt carry).
• Run: use all official feed zones (walk 5-10 s if needed to drink without choking).

Training test: the drink you use in the race must have been tested in a long session. Never introduce a new product on race day.

Session goal: match your nutrition accordingly

Not all long rides are equal. The goal changes everything:

Zone 2 endurance ride (easy pace, 3-4 h): You can intentionally lower carbs in the first hour to train your body to oxidise fat ("train low" strategy). Do not drop below 30-40 g/h if you plan a moderately intense portion. Prefer solid foods (banana, cereal bar, sandwich). Goal: burn 600-800 kcal from fat stores during the ride.

Threshold ride or brick (moderate to high intensity, 3 h with 1 h hard): No train low. Target 60-80 g carbohydrates/h from the start. Liquid carbs (isotonic drink) complement solids. The intense portion must be fuelled, not done on empty.

Brick ride followed by run (2-3 h bike then 30-45 min run): Eat more than for an equivalent solo ride. In the last 30 minutes on the bike, add 15-20 g fast carbs (gel or drink) to start the run without a blood sugar dip.

Fuelling windows: timing and practical sources

The 20-minute rule: eat every 20-30 min, not when you feel hungry. Hunger is a 30-45 min lag behind actual glycogen depletion.

What works well on the bike in training:

• Bananas (1 banana = 27 g carbs, easy digestion)
• Muesli or fig bars (25-40 g carbs, no fatty coating)
• Dates or dried fruit (concentrated fast sugars, 1 handful = 20-25 g carbs)
• White bread sandwich + jam + a pinch of salt (testable on a 3 h+ ride)
• Gels: 1 every 45 min maximum, always with water. Do not stack them.

Drinks: 500-700 ml/h light isotonic (6-7 g carbs/100 ml + sodium). In summer, hydration +20%, carbs stable.

Common mistake: full solid meals on a long ride (full sandwich, cheese, charcuterie). Digestion time is longer on the bike and disrupts threshold efforts that may occur. Stick to simple foods, low fibre.

Recovery after a long ride: the first 30 minutes

The post-ride recovery window is real but often misunderstood. The goal is not to "maximise anabolism" but to replenish muscle glycogen before the next session.

Within 30-45 min after finishing:

• 40-60 g carbohydrates + 20-30 g protein. Examples: rice + chicken, skyr + banana + cereal, omelette + bread, or protein shake + fruit juice.
• 500 ml water + electrolytes.

What is NOT a priority: specific amino acids (BCAAs, leucine), cryotherapy, high-dose antioxidant juices. The brake on adaptation is energy availability, not "recovery supplements".

Sign of correct recovery: you should be able to do a moderate session the next morning without dead legs. If not, you did not eat enough during the ride or right after.

The amateur triathlete paradox

High training volume, feeling of nutritional immunity ('I burn so much it compensates'). Result: chronic carbohydrate deficits on high-load days, unnecessary protein excess, and missed recovery windows.

Studies on amateur Ironman athletes (Stellingwerff 2017, Thomas 2016) show 60-70% under-consume carbohydrates on high-volume days (target: 6-10 g/kg) and 40% have chronic iron deficiency, especially women. This is not complex physiology: it's a plate structure problem.

The plate model by day type

Light day (<1h session): vegetables 1/2 plate, protein 1/4 (meat/fish/egg/legumes), carbs 1/4 (rice, potato, pasta). No special manipulation.

High-load day (>2h session): carbs to 1/2 plate. Not just at dinner: spread across lunch AND dinner. Most amateurs do the opposite (vegetables 1/2 at lunch, carbs 1/2 at dinner) when you need to load BEFORE the next morning's long session.

Post-long session (60-90 min after): real anabolic window: 1 g/kg carbs + 0.3-0.4 g/kg protein within 30-45 min. Rice + chicken or yoghurt + banana. This window is often skipped despite being the most impactful.

The 3 nutrients to prioritise

Iron (especially women + high-mileage runners): plantar haemolysis (red blood cell breakdown with each stride) + sweat losses. Ferritin deficit (<30 microg/L) = unexplained fatigue that looks like overtraining. Blood test recommended 1x/year. Sources: red meat 2x/week, lentils, spinach + vitamin C for absorption.

Omega-3: chronic training inflammation controlled by the omega-6/omega-3 ratio. 2 portions of fatty fish/week (mackerel, sardine, salmon) or 2g EPA+DHA/day supplement during high-load periods.

Magnesium: lost in sweat. Night cramps = classic sign. 400 mg/day (Brazil nuts, cocoa, green vegetables). Do not exceed 700 mg/day (laxative effect).

Chronic inflammation: a hidden brake

Every training session creates acute muscular inflammation: that's necessary to trigger adaptation. The problem is when this inflammation never fully subsides between sessions.

Chronic low-grade inflammation = inflammatory markers (IL-6, CRP) constantly elevated, without necessarily identifiable pain. Concrete consequences: slower recovery between sessions, increased tendinopathy risk, weakened immunity (repeated winter respiratory infections), persistent fatigue despite sleep.

Ironman triathletes in prep with volumes over 10 h/week are particularly exposed. Nutrition doesn't replace recovery, but it modulates the speed and extent of inflammation.

Foods that reduce inflammation

Omega-3: oily fish (sardines, mackerel, salmon) 2-3 times a week or EPA/DHA supplement 1-2 g/day. Omega-3s directly modulate inflammatory pathways (prostaglandins).

Polyphenols and antioxidants: berries (blueberries, cherries, strawberries), turmeric (combine with black pepper for bioavailability), fresh ginger. Tart cherries have a measured effect on post-long-run DOMS.

Cruciferous vegetables: broccoli, cauliflower, rapini - rich in sulforaphane (documented anti-inflammatory effect). 2-3 portions per week is enough.

Extra virgin olive oil: source of oleocanthal, a natural anti-inflammatory. Use raw (dressing, bread) to preserve heat-sensitive polyphenols.

Adequate hydration: even mild dehydration (1-2% of body weight) increases inflammatory markers. Drink 35-40 ml/kg/day on training days.

What worsens inflammation: common traps

Alcohol: even 1-2 drinks per day disrupts overnight protein synthesis and raises cortisol. Direct impact on muscle recovery speed. It's not a ban, it's a choice: if you're targeting sub-10h30, the day after a long run is not the right day.

Ultra-processed foods and excess omega-6: sunflower/corn oils in large amounts, crisps, biscuits, ready meals. The Western omega-6/omega-3 ratio is 15:1 - the ideal is 4:1. This imbalance is pro-inflammatory.

Fast sugars outside training windows: a rollercoaster blood sugar (insulin spike then crash) activates inflammatory pathways. Simple carbs = OK around sessions, limit at other times.

Chronic caloric deficit: trying to lose weight during Ironman prep raises cortisol and inflammation. If you need to lose weight, target base periods with low volume, not peak blocks.

What the science says about the metabolic window

After an endurance session, your muscles are like dry sponges: GLUT4 glucose transporters migrate massively to the cell membrane, enabling very rapid glucose absorption -- even without insulin. This hyperpermeability to glucose lasts approximately 30 to 60 minutes, then diminishes progressively over 2 to 3 hours.

In parallel, muscle protein synthesis (MPS) is elevated for 24 hours post-session, with a peak in the first 2 hours. Providing protein in this window accelerates the repair of muscle micro-tears created during effort.

Conclusion: yes, a window exists. But its importance depends on context.

When the window is truly critical

The post-session window is critical in three situations: (1) double training day (AM+PM): you have less than 8 hours to reload before the next session. Without rapid recharge after the AM session, you arrive empty for the PM. The window is not an extra advantage -- it is a necessary condition.

(2) 3-day block or longer: when chaining heavy days (triathlon training camp, peak week), every window counts to prevent fatigue from accumulating into an irrecoverable debt.

(3) Long session of more than 90 minutes fasted: if you trained fasted or very lightly fuelled, your glycogen stores are significantly depleted and rapid recharge accelerates recovery.

In other cases (single session under 90 min, full meal planned within 2 hours), the urgency of the window is much more relative. You can shower, put your bike away, and eat afterwards -- the impact on recovery will be minimal.

The optimal protocol in practice

Within 30 minutes post-session (urgent): 60 to 80 g of high-glycaemic-index carbs (white rice, white bread, banana, recovery gel) + 20 to 25 g of complete protein (Greek yoghurt, skyr, whey or casein protein shake). This combination maximises glycogen resynthesis (glycogen synthase activated at maximum by post-carb insulin) and starts muscle repair.

Liquid or solid? In endurance sports, the stomach is often disturbed just after effort. A liquid shake (chocolate milk, protein-banana smoothie) is more easily tolerated than a solid meal. Wait 20 to 30 minutes before eating solid food if you have nausea.

Chocolate milk: scientifically validated (Cockburn studies, 2010-2012). Optimal carb-to-protein ratio (~4:1), contains calcium and sodium, easy to transport. Per 500 ml: approximately 52 g carbs + 17 g protein. Practical and affordable option.

Then (1 to 2 hours later): a full balanced meal (complex carbs + protein + fats + vegetables). The urgency has passed, eat normally.

Why sodium is crucial on an Ironman

Sodium is the main extracellular electrolyte. It plays three key roles during prolonged effort:

Water retention: sodium retains water in the vascular compartments. Without sufficient sodium, consumed water passes into the tissues without maintaining blood volume -- cardiovascular performance drops.

Neuromuscular transmission: muscular contractions depend on sodium/potassium electrochemical gradients. Mild hyponatraemia (low sodium) slows nerve impulse transmission -- legs 'stop responding'.

Intestinal absorption of carbohydrates: the SGLT1 co-transporter uses sodium to bring glucose into enterocytes. Without adequate sodium, carbohydrate absorption is less efficient.

Sweat sodium losses vary enormously between individuals: from 400 to 1700 mg/L depending on genetics, acclimatisation, and sweat rate. A heavy sweater (white salt stains on clothing) can lose 2 to 3 g of sodium per hour in the heat.

Estimating your losses and choosing your sodium source

Estimating your sweat sodium rate: in the absence of a professional sweat test (Precision Hydration, Gatorade Sports Science Institute), use these practical indicators:

• White stains on face/kit after a long session = very salty sweat (>1000 mg/L probable)
• Sweat that stings the eyes or very salty taste = same
• Transparent sweat with no deposit = probably below 700 mg/L

Sodium sources in racing:

• Isotonic energy drinks: 300 to 700 mg of sodium per 500 mL depending on brand. Useful if you consume enough fluid.
• Salt tablets / electrolyte gels: 200 to 500 mg per unit, convenient format to adjust in real time. Brands: SaltStick, Precision Hydration tabs, High5.
• Chicken broth or soup at aid stations (Ironman France, IMEM): 800 to 1200 mg per cup -- very effective in the second half of the marathon.

Basic rule: do not attempt to replace 100% of losses -- the body tolerates a moderate deficit. Target 500 to 1000 mg/h depending on your sweat profile.

Building your sodium strategy for the Ironman

Bike phase (0 to 180 km): the longest phase -- this is where sodium deficit accumulates silently. Consume your isotonic energy drink regularly + add 1 salt tablet every 45 to 60 min if you sweat heavily or it is hot (>25 degrees). Target: 600 to 900 mg/h.

Run phase (0 to 42 km): the phase where the consequences of the deficit become visible. If you arrive at the marathon with nausea or legs that stop responding, it is often a sodium deficit (not fuel). Consume the broth offered at aid stations (if available), keep 1 salt tablet every 5 km. Do not force if nausea is present -- reduce intensity first.

Week before race (avoid depletion): do not go to the sauna, do not reduce your salt intake -- this is the time to have optimal reserves. Drink normally, eat normally with salt (no artificial sodium restriction).

MANDATORY training test: never test a new sodium source for the first time in a race. Test your strategy on 2 to 3 long bike rides (3h+) before race day.

The six nutrients to monitor closely

Complete protein: plant proteins are often incomplete (lacking one or more essential amino acids). Solution: combine complementary sources throughout the day -- legumes + grains (lentils + rice, hummus + pita, tofu + quinoa). Quinoa and soy are the rare complete plant proteins.

Non-haem iron: iron from plants (non-haem) is absorbed 2 to 3 times less efficiently than animal iron (haem). To maximise absorption: always combine with vitamin C (bell pepper, lemon, kiwi) and avoid tea/coffee within 2 hours of an iron-rich meal.

Vitamin B12: absent from plant foods (except nutritional yeast and fortified products). Supplementation is mandatory for vegans: 2000 micrograms per week in one dose or 250 micrograms per day.

Omega-3 (EPA/DHA): flaxseeds and walnuts provide ALA (precursor), but conversion to active EPA/DHA is low (5 to 10%). For endurance athletes: direct supplementation with algae oil (DHA/EPA source without fish).

Creatine: omnivores get 1 to 2 g/day via meat; vegetarians have lower muscle creatine stores. Supplementation (5 g/day creatine monohydrate) can improve short endurance performance and recovery.

Zinc: present in legumes and seeds but in less bioavailable form. Soaking legumes before cooking reduces phytates and improves zinc absorption.

Meeting protein needs in long-distance endurance

A triathlete preparing for an Ironman needs 1.6 to 2 g of protein per kg of body weight per day to support muscle recovery and prevent catabolism (lean mass breakdown during high volume phases).

For a 70 kg athlete, this represents 112 to 140 g of protein per day -- achievable but requiring planning with plant-based eating.

High-protein plant sources (per 100 g):

• Textured soy protein: 50 g
• Tempeh: 20 g
• Edamame: 11 g
• Cooked lentils: 9 g
• Firm tofu: 17 g
• Hemp seeds: 32 g
• Skyr / Greek yoghurt (vegetarian): 10 to 17 g

Post-session window: the rule of 20 to 40 g of protein within 30 to 60 min post-effort still applies. Pea or rice protein shake (or a blend of both for a complete profile) + a carbohydrate source.

Glycogen and energy management over long distance

Vegetarian and vegan diets are naturally high in complex carbohydrates -- an advantage for building glycogen stores. Whole grains, legumes, and tubers provide quality carbohydrate intake.

During effort: standard energy gels and drinks are mostly plant-based (check gelatine capsules). Medjool dates, mashed bananas, and oat bars are excellent natural alternatives for moderate efforts.

Carb-loading before race: the classic protocol (8 to 10 g/kg/day for 48h) remains identical for vegetarians. Prioritise white rice, pasta, white bread, and fruit compote (avoid legumes in the 24h before to reduce gastrointestinal risk).

Warning sign: chronic fatigue, slow recovery, and anaemia are often signs of deficiencies (B12, iron, zinc) rather than protein insufficiency. Get a complete blood test (iron panel, B12, ferritin) every 6 months during intensive preparation.

Why weight is not the only relevant indicator

The power-to-weight ratio (W/kg in cycling, speed/weight in running) is a performance indicator for climbing -- but it is rarely the limiting factor in long-distance triathlon on flat or rolling terrain.

Two athletes weighing 70 kg do not have the same body composition. An athlete with 12% fat mass and 60 kg of lean mass produces more power and recovers better than an athlete at 25% fat mass for the same total weight.

The scales do not tell the full story: muscle is denser than fat. An athlete in recomposition (simultaneous lean mass gain and fat loss) can maintain the same total weight while improving performance.

What research shows on endurance athletes: targeting very low fat mass (<8% in men, <16% in women) beyond an individual threshold increases the risk of stress fractures, hormonal disorders (in women: loss of cycles; in men: lower testosterone) and overtraining.

When and how to optimise body composition

The golden rule: never cut calories during high-load phases. During a build or peak block (volume >10h/week), your body needs sufficient calorie intake for protein synthesis, glycogen storage, and immune function. Too large a calorie deficit during intensive phases raises cortisol, disrupts sleep, and blocks progression.

The right window: the base. The base phase (low intensity, moderate volume) is the only time you can slightly reduce calories (300 to 500 kcal/day below maintenance) without compromising adaptations. Weight loss will be slow (0.3 to 0.5 kg/week max) -- this is intentional.

Protecting lean mass: if you reduce calories, maintain or increase protein intake (1.8 to 2 g/kg/day) and continue strength training. Calorie restriction without sufficient protein intake burns muscle alongside fat.

Objective measurement: daily weighing is noisy (1 to 2 kg variations from hydration and glycogen). Use a 7-day rolling average, or measure body composition (bioimpedance or skinfold calipers) every 6 to 8 weeks.

Warning signals: when to stop trying to lose weight

Physical signals not to ignore:

• Chronic fatigue that does not ease even with rest
• Insufficient recovery between sessions (persistent DOMS, rising resting HR)
• Recurring stress injuries (shins, feet, hips)
• In women: irregular or absent menstrual cycles
• Obsession around food or post-meal guilt

The race week weight paradox: in the 5 to 7 days before an Ironman, the body stores glycogen (1 g of glycogen retains approximately 3 g of water). It is normal to gain 1 to 2 kg in race week -- this is good news, not a problem. Do not panic or reduce carbohydrates.

The right question to ask yourself: am I eating enough to train and adapt, or am I compensating for a negative body image with restriction? A sports nutritionist can help distinguish rational optimisation from counterproductive restriction.

The two classic pre-race dinner mistakes

Mistake 1: the excessive pasta party. Loading massively on carbohydrates the night before the race is a myth: muscle glycogen rebuilds over 24 to 48 hours, not overnight. An overly large pre-race dinner -- 700 g of pasta + bread + sugary dessert -- causes bloating, difficult digestion and disrupts sleep. Effective carb-loading happens over the 2 to 3 days before the race, not in one shot.

Mistake 2: 'risky' foods. After a meal rich in fibre (legumes, raw vegetables, brassicas like broccoli or cabbage), fat (sauced meat, fatty cheeses, frying) or alcohol (even a beer), digestive effects are unpredictable under effort. Many triathletes have discovered these 'forbidden foods' during a race -- not under ideal circumstances.

The basic rule: favour known foods, low in fibre, quick to digest, without novel experiences. The night before a race is not the time to try a new restaurant.

What to eat and in what timeframe

The ideal meal (3 to 4h before bedtime, or 10-12h before the start):

• Easily digestible carbohydrates: white rice, white pasta, white bread, steamed potato. Moderate portion (150-200 g dry weight for 70 kg).
• Lean proteins: grilled chicken, turkey breast, plain tofu, poached or soft-boiled egg. Avoid sauced or fatty meat.
• Small amount of fat: a drizzle of olive oil, not excessive butter.
• Cooked vegetables (not raw) in small amounts if needed, or nothing if stomach is sensitive.
• Hydration: 500 ml of water or isotonic drink in the 2h after dinner. Avoid drinking 1h before bed to prevent sleep interruption.

Timing:

• Ideally dine 3h before bedtime (advanced digestion = better sleep quality).
• Cut solid food 2h before sleep.
• Avoid alcohol: even 1 glass reduces sleep quality by 20-25% (higher nocturnal heart rate, less deep sleep).

What works for you: the best pre-race dinner is one you have already eaten before a long training session without digestive issues. Reproduce the familiar, do not improvise.

Magnesium: cramps, sleep and energy metabolism

Magnesium is the mineral most often depleted in endurance athletes: sweat eliminates 30-50 mg/hour, and the chronic perspiration of Ironman training (10-15h/week) creates a structural deficit even with a balanced diet.

Role: cofactor for more than 300 enzymatic reactions, including ATP synthesis (energy production), muscle relaxation (calcium antagonist) and nervous system regulation (sleep quality).

Signs of deficiency: nocturnal cramps, sleep disturbances (difficulty falling asleep, non-restorative sleep), disproportionate fatigue, irritability, involuntary muscle contractions.

Recommended intake: 400-450 mg/day for an athlete in intensive training (vs 300-350 mg for the general population). Food sources: pumpkin seeds (262 mg/100g), almonds (270 mg), cooked spinach (87 mg), 85% dark chocolate (228 mg), legumes.

Supplementation if deficient: magnesium glycinate or bisglycinate (better absorption, fewer digestive issues than oxide). 200-400 mg in the evening. Avoid magnesium oxide (laxative effect, bioavailability < 4%).

Iron and zinc: two often-ignored deficiencies

IRON -- direct impact on VO2max: Iron is the central component of haemoglobin (oxygen transport) and myoglobin (muscular oxygen reserve). An iron deficiency -- even without declared anaemia (latent deficiency = ferritin < 30 ng/ml) -- reduces aerobic capacity by 10-20%.

At-risk groups: women (menstrual losses), high-mileage runners (intraluminal foot haemorrhage from impact), vegetarian/vegan diets (non-haeme iron less absorbable).

Recommended monitoring: ferritin + full blood count every 6 months during intensive training. Target ferritin > 50 ng/ml for endurance athletes (not just > 12 ng/ml as in general medicine).

Haeme iron sources (better absorbed): red meat, liver, mussels. Non-haeme sources: lentils, spinach, tofu -- eat with vitamin C (kiwi, red pepper) to double absorption. Avoid coffee/tea in the hour after an iron-rich meal.

ZINC -- immunity and muscle recovery: Zinc is essential for muscle protein synthesis, wound healing and immune response. Endurance athletes eliminate 2x more zinc than sedentary individuals (sweat + urine). Common deficiency during intensive training: recurrent colds, slow healing, loss of taste and appetite.

Recommended intake: 15-20 mg/day during intensive training. Sources: oysters (71 mg/100g -- densest source), beef, pumpkin seeds, legumes, cashews.

Supplementation if needed: zinc citrate or gluconate, 15-25 mg/day with a meal (avoid on an empty stomach = nausea). Do not exceed 40 mg/day routinely (interaction with copper absorption beyond this).

Why your stomach lets you down on race day

Long-distance triathlon effort causes intestinal ischaemia: blood flow is redirected to active muscles, leaving the digestive tract under-perfused. In this state, the gut becomes hypersensitive: a gel tolerated in training at low intensity can cause nausea or abdominal cramps at race intensity.

Three aggravating factors on race day compound this: dehydration (slows gastric emptying), pre-race stress (inhibits intestinal motility via the autonomic nervous system), and heat (diverts even more blood from the intestines).

Conclusion: it is not the product that is the problem, it is the combination of product + intensity + cumulative fatigue. A test under real conditions is irreplaceable.

How to simulate race conditions in training

Basic rule: test on long sessions. A gel ingested at 65% of max HR for 30 min tells you nothing about your tolerance at 80% max HR after 4 h of cycling. Useful tests happen on:

• Long brick (3-5 h bike + 45 min run): the most representative context
• 4 h+ bike ride at race intensity (zone 3): testing carbohydrate tolerance over time
• 2 h+ long run: testing gels and drinks during post-bike running

Test one element at a time. If you change the gel AND the drink AND the intake frequency simultaneously, you will not know what caused the problem. Methodology: 1 variable per long session.

Reproduce exactly the concentration and frequency. 60 g of carbs/h with 500 ml of water is very different from 60 g with 250 ml: a hypertonic solution in the stomach slows gastric emptying. Note the water volume per gel/bar tested.

Building your protocol step by step

Base phase (4-5 months before race): experiment freely. Test different brands, concentrations, solid vs liquid. The goal is not performance, it is an inventory of what is tolerated.

Build phase (2-3 months before): refine the bike protocol (solid/liquid ratio, hourly intake frequency). Lock down the gel or drink for the T2 transition. Do not change after this phase.

Peak phase (4-6 weeks before): reproduce the race protocol exactly during the long brick. Same products, same frequencies, same water volume. If a problem arises: now is the time to fix it, not on race day.

The week before: test the products available at the official race aid stations (Ironman uses specific partners). If you do not recognise the gel, carry your own in a pocket.

Document to keep: note your final protocol in a single table (H+0 = gel X + 200ml water, H+1 = bar Y + 300ml drink, etc.). Give it to a support person on race day for the special needs bag.

Why GI issues occur in Ironman

The digestive system is very sensitive to the physiological stress of long-distance racing. Several mechanisms converge:

1. Redistribution of blood flow: at high intensity, the body redirects up to 80% of blood flow to active muscles. The small intestine -- responsible for carbohydrate and water absorption -- then operates with minimal blood flow, slowing and degrading absorption.

2. Carbohydrate concentration too high: gels and drinks at high concentration (> 8-10% carbohydrates) are not absorbed directly -- they draw water from the blood into the intestine by osmosis, creating osmotic diarrhoea. This is the classic problem of the triathlete who mixes a hyperosmolar energy drink with gels without water.

3. Sodium/water imbalance: drinking too much water without sodium dilutes blood plasma. Mild hyponatraemia creates nausea and a bloating sensation.

4. Intestinal ischaemia: over long durations or at high intensity (especially if bike pace is too high), the intestine can suffer transient micro-ischaemia causing pain, nausea and diarrhoea.

5. Psychological stress: cortisol activates the sympathetic nervous system and directly slows intestinal motility in some people. Pre-start nausea or intestinal problems on a first Ironman marathon are often partially psychological.

Prevention protocol before and during the race

Before the race (D-3 to D-1):

• Eliminate foods high in insoluble fibre (legumes, wholegrain bread, seeds, raw vegetables in large quantities). This is not the time to experiment.
• Reduce dairy products if you usually have sensitivity.
• D-1 breakfast: familiar, tested in training, low in fibre (white bread, rice, banana).
• Hydration with electrolytes (sodium) the day before: 500 mg sodium for each 500 ml of water.

During the race:

• Do not mix isotonic drinks and concentrated gels. If your drink already contains carbohydrates, take your gels with WATER, not the drink. The total concentration in the stomach should not exceed 6-8%.
• Glucose+fructose (ratio 2:1 or 1:0.8) > pure fructose gels for sensitive stomachs: fructose alone quickly saturates the intestinal GLUT-5 transporter and creates osmotic diarrhoea.
• Rule of 200 ml every 20 min instead of gulping 500 ml at once -- absorption is more regular.
• Slow food intake if nauseous: reduce intake by 50% for 20-30 min, continue electrolytes, resume progressively.

Ironman run: prioritise liquid. The stomach tolerates solid foods much less while running than cycling (stride impacts). Diluted cola (50/50 with water) remains a reliable option in the second half of the marathon -- simple carbs + caffeine + sodium.

Gut training: training your intestine before the race

The intestine adapts to training like muscles -- you can literally train it to absorb more carbohydrates during effort with fewer symptoms. This adaptation takes 3 to 6 weeks.

Gut training protocol:

1. Replicate race conditions in training. Eat and drink EXACTLY what you plan in the race, at the same intervals and the same intensities. No sessions on plain water followed by a race with 80g of carbohydrates per hour.
2. Progressively increase intake. Start at 40-50g of carbohydrates/hour, increase by 10g per week until reaching the target 80-90g/hour. Symptoms decrease as intestinal transporters (SGLT-1, GLUT-5) adapt.
3. Train the intestine in race posture. Brick sessions (bike + run) are the best GI training windows as they replicate the post-bike stress of running digestion.
4. Keep a GI journal. Note after each long outing: amount ingested, product type, symptoms, intensity. Patterns reveal themselves in 4 to 6 weeks.

What you cannot eliminate: race-day psychological stress and blood flow redistribution at maximum intensity. Prevention relies on appropriate pacing (not going out too hard on the bike) as much as on nutrition.

How caffeine improves performance

Caffeine blocks adenosine receptors, the molecule that signals fatigue to the brain. Result: perceived effort is reduced at identical intensity, and sustainable peak power increases by 2-4% on average for endurance efforts (meta-analyses on marathons, cycling, triathlon).

Positive side effects: release of free fatty acids (spares glycogen early in effort), improved concentration and reaction time, reduced perceived muscle pain.

Negative side effects if overdosed: tachycardia, tremors, anxiety, diarrhoea or intestinal urgency (high risk during the marathon if taken late), accelerated diuresis (compensate with hydration).

Dosage and protocol for an Ironman

Effective dose: 3-6 mg/kg body weight. For 70 kg: 210-420 mg. A single 400 mg dose is not recommended (too sharp a peak, high GI risk). 200-250 mg split into 2 doses is more tolerable.

Timing for an Ironman: caffeine reaches plasma peak in 45-60 min and remains effective for 3-4 h.

• Dose 1 (main): 45-60 min before the start. 200 mg via caffeine gel or strong coffee (double espresso = 120-140 mg). This is the most important dose.
• Dose 2 (top-up): km 90-100 of the bike (3-4 h into the race). 100 mg via caffeine gel. Target: effect lasts until mid-marathon.
• Dose 3 (optional): km 25-28 of the marathon if you feel the dip. 100 mg maximum. High GI risk if the gut is already stressed.

What to avoid: caffeine via isotonic drink (imprecise dosage), caffeine morning of a long bike ride on D-3 (disrupts sleep if taken after 14:00).

Habituation and washout: optimising the benefit

Habituation reduces the effect: if you drink 3 coffees a day, your brain has developed more adenosine receptors. Race caffeine will have a smaller effect. The solution: gradual reduction over 7 days before the race.

Washout protocol (optional, effective):

• D-7 to D-5: reduce to 1 coffee/day
• D-4 to D-2: switch to decaf or weak green tea
• D-1: zero caffeine
• D-0 (race): normal dose 45 min before start. The effect will be noticeably stronger.

Washout side effects: headaches days 2-4 (normal, variable duration), increased fatigue, irritability. Plan this during a deload week, not an intensive training week.

Individual sensitivity: some athletes metabolise caffeine quickly (CYP1A2 fast genetic variant) and get only 2-3 h of effect. Others metabolise it slowly and suffer sleep disruption 8 h after intake. Test your response on 2-3 long training sessions before race day, never try it for the first time in a race.

Sodium, not just water

Dehydration is a real risk but overestimated. Hyponatraemia is underestimated and potentially fatal.

Sodium by the numbers:

• Average sweat rate: 500-1500 ml/h (varies with heat and genetics)
• Sweat sodium concentration: 500-2000 mg/L (highly variable, especially in 'salty sweaters' who leave white traces on clothing)
• A 10-hour Ironman = 5-15 g of sodium lost without replacement

The telltale sign: white patches on your face or shorts after training = you lose a lot of sodium. Your supplementation must be aggressive.

What to avoid: drinking only water for 10 hours of effort. Sodium drops, cells swell, symptoms resemble dehydration (cramps, nausea, confusion) but drinking more water makes everything worse.

Signals of sodium depletion

Early signals (bike km 100-130):

• Unexplained muscle cramps even when well hydrated
• Feeling of bloating and heaviness
• Mild nausea without clear digestive cause
• 'Aching all over' with no obvious cause

Advanced signals (marathon km 20-30):

• Increasing headaches
• Mental confusion, difficulty doing simple maths (pace, km remaining)
• Intense salt cravings (the brain signalling the deficit)
• Spreading cramps, inability to run normally

Emergency signals (medical):

• Seizures, loss of consciousness, repeated vomiting

If these signals appear: STOP, race medical immediately.

Supplementation protocol

Target: 500-1000 mg sodium per hour of intense effort, more in heavy heat or if you are a salty sweater.

Sources:

• Electrolyte gels (SiS, GU Roctane, Maurten 160): 50-100 mg sodium/gel. Insufficient alone.
• Electrolyte tablets (SaltStick, Precision Hydration PH 1000): 250-500 mg/tablet. Main source.
• Race nutrition from aid stations (Ironman formulas): 200-300 mg/bottle.

Ironman protocol (70 kg, moderate heat):

• Bike: 1 electrolyte tablet (500 mg) every 45 min + water ad libitum + race drink
• Marathon: 1 tablet every 30-40 min (intensity rises, sweat too)
• Total target: 4-5 g sodium/10h. Do not 'catch up' if you miss a dose. Just resume the rhythm.

Mandatory test on long sessions (4h+), never try it for the first time in a race.

Personalising to your profile

Sodium needs vary by a factor of 4 between individuals. The most reliable test: look at your clothing after a long session in heavy heat.

Little white residue - moderate need: 300-600 mg/h, standard tablets. Lots of white residue - salty sweater: 700-1500 mg/h, high-dose tablets (PH 1500, LMNT) + sodium pre-loading (2 g 90 min before the start).

Pre-race loading: for salty sweaters or very hot races: 1 g of sodium in 500 ml of water the evening before + 1 g in 500 ml the morning of the race (H-90 min). Effect: filling the tank before effort, delaying depletion.

Testing in real conditions: add 250 mg extra on a 3-hour session, note cramps, the feeling of lightness at the end, mental state. Adjust for the next session.

The 3 early warning signals

1. Reflux or nausea within 5 min after a gel. Signal: your stomach says no to concentrated carb form. Consequence = it will reject the next 2 gels too. Do not insist, switch vector immediately (see plan B).

2. Sudden 5-10 min power drop on bike without climb or wind. If power drops 20 W without external reason AND you are past 90 min of racing, it is a mild hypoglycemia signal. You have 15-20 min to react before complete blackout.

3. Stomach cramp or bloat. Pain in upper or mid abdomen, bloating. Signal of blocked gastric emptying. Often linked to mild dehydration (carb concentration too strong for available fluid) or too high intensity during ingestion.

These 3 signals hit 30-40% of amateur athletes in a 70.3, 60-70% in full Ironman. It is not about testing their presence but knowing what to do when they arrive.

Plan B: reset at the next aid station

Gel rejection: at next aid station, take 500 ml plain water (no sports drink) + 1 banana piece OR 1 orange wedge. Solid vector or water + fruit = better tolerated than gel after rejection. Wait 10 min before trying half a gel.

Hypoglycemia: immediately cut 15% bike power (or run pace). Absorb 60 g fast carbs over the next 15 min: 1 gel + 500 ml sports drink + 1 fruit piece. Do not slam 2 gels at once, it creates fresh nausea. Return to target intensity only when power comes back naturally.

Stomach cramp: stop all concentrated intake for 20 min. Plain water only, 100 ml sips every 5 min. Cut intensity 20%. Once cramp passes, resume nutrition in diluted form: sports drink diluted 50/50 with water, no gel before 30 min.

Cross-cutting rule: on any nutrition failure, intensity must go down at the same time. Grinding on with a shut stomach = guaranteed explosion on the run.

Preparation: avoid the failure rather than manage it

Test nutrition in training, not in race. Your nutrition strategy must have been tested 4 to 5 times in long sessions with the SAME products, SAME timings, SAME quantities as race day. No improvising with race aid station gels.

Carb / fluid ratio. Documented rule: max 60 g carbs / hour with at least 500 ml fluid in the same hour. Beyond that, the stomach cannot follow. If you aim for 90 g/h ('gut training' technique), you need 3-4 months of regular digestive training, not starting in race.

Adapt to temperature. In heat (>25°C), reduce gel concentration and increase fluid. One gel with 200 ml plain water goes down better than one gel with 100 ml already concentrated sports drink.

The gel rebound. Big trap: taking 3 gels in a row at end of bike 'to attack the run in shape'. Almost systematic result: nausea at km 5 of the half-marathon. Space out, never stack.

Why hydration outside sessions is critical

Triathletes training 10-15 h per week lose between 1 and 2 liters per hour of sport (variable by temperature and intensity). Over a 12 h training week, that is 12 to 24 liters lost through sweat. Even drinking during each session, the between-session deficit accumulates.

Campbell et al. (2021) show that dehydration of only 1-2% body weight (700-1400 ml for 70 kg) increases resting cortisol by 12%, reduces deep sleep quality by 8%, and extends muscle recovery time by 15-20%.

These effects occur well before thirst. Thirst is a delayed signal (active when deficit is already 2-3%). Athletes training in hot weather or altitude are particularly exposed as basal losses are higher.

Estimate your daily need outside sessions

The basic formula. Hydration need outside sessions = 35 ml x body weight in kg + post-training compensation.

Example for 70 kg: 35 x 70 = 2450 ml base (food intake (soups, fruits, vegetables) covers about 800-1000 ml, so 1450-1650 ml of pure fluid to drink outside sessions).

Post-training compensation. Validated practical rule: drink 1.5 liters of fluid per kg lost during the session. To estimate loss: weigh before and after (without clothes, after brief toweling). 1 kg lost = 1 liter of sweat loss. The 1.5 factor compensates for diuresis (some drunk fluid is excreted, not absorbed).

Quick hydration status tests:

• Urine color on waking: pale yellow (lemon) = OK, dark yellow = mild deficit, amber or brown = significant deficit to correct before morning session
• Micturition frequency: fewer than 3 times per day = chronic under-hydration
• Morning weight: variation > 1% in 24 h without muscular reason = possible fluid deficit sign

Beware of over-rationalization. Drinking more is not neutral. Exercise hyponatremia (sodium too diluted by excess plain water) can occur in slow Ironman athletes (>14 h) who drink plain water at every aid station without electrolytes. The risk is rare but real on long format.

Practical habits to maintain hydration status

The morning bottle. Drink 500 ml of water on waking before coffee. The body is systematically in mild deficit after 7-8 h without intake. This single habit halves the morning deficit before even going to train.

Glass of water before each meal. 500 ml before each main meal (lunch + dinner) = 1 extra liter automatically, without cognitive effort. Water before meals also has a documented satiety effect (Davy et al., 2008: -13% caloric intake at the subsequent meal).

Hydration in hot weather. Add 500 ml per 10 degrees above 20 degrees ambient daily temperature. Example: 30 degrees + = add 1 liter to base. In high humidity (>70%), add 500 ml more (sweating loses cooling efficiency and basal fluid loss increases).

The coffee and tea trap. Coffee and tea have a mild diuretic effect on the first intake of the day, negligible after acquired tolerance. This does NOT justify counting them negatively in the balance. 1 cup of coffee contributes 150-200 ml net to fluid balance despite caffeine.

Electrolytes outside sessions. If you sweat a lot at rest (heat, stress) or are a salty sweater (white salt traces on post-effort kit), add a pinch of quality salt to your morning water or 1 electrolyte tablet diluted in 500 ml of water once a day.

Warning signs to recognize during the race

Endurance hypoglycemia occurs when glycogen reserves are depleted and carbohydrate intake has been insufficient. Signs appear progressively:

Early signs (dropping blood sugar, still easily reversible):

• Unusual muscle weakness, cotton-wool legs
• Difficulty maintaining target pace without extra effort
• Slowed thinking, difficulty calculating or concentrating
• Feeling of emptiness or gastric hollowness despite no clear hunger

Late signs (low blood sugar, treat urgently):

• Trembling, dizziness, blurred vision
• Pallor, cold sweats disproportionate to effort
• Confusion, inability to respond to volunteer instructions
• In extreme cases: loss of consciousness (medical emergency)

Distinguishing from normal fatigue: endurance fatigue is diffuse and gradual. Hypoglycemia often arrives more suddenly, with a marked cognitive component (confusion, difficulty thinking).

Fast correction protocol on the bike and during the run

On the bike (easier to correct):

1. Reduce intensity immediately (leave target power zone, drop back to zone 2)
2. Consume 40 to 60 g of fast-absorbing carbohydrates: gel + water, or banana + isotonic drink
3. Wait 10 to 15 minutes before raising intensity again - let glucose time to enter circulation
4. Do not panic and overcompensate by eating everything available: risk of GI distress later in the race

On the run (harder):

1. Walk immediately to reduce glucose demand
2. Take a gel with water at the next aid station (do not keep running between stations hoping to hold on)
3. If confusion has set in: stop, sit, signal a volunteer

Golden rule: if you are unsure between hypoglycemia and a simple energy dip, treat as hypoglycemia. The cost of an unnecessary gel is negligible vs the cost of untreated hypoglycemia.

Prevention: the real remedy is in nutritional planning

Main avoidable causes:

• Starting the race too fast (zone 4-5 in the first bike kilometers burns glycogen 3x faster than zone 2)
• Skipping an aid station ('I feel good, I will catch up later'): classic mistake - hunger always arrives too late
• High pre-race stress elevating cortisol and accelerating depletion
• Short or restless pre-race night (the liver stores less glycogen under sleep deprivation)

Minimum planning:

• Bike: 60 to 90 g carbohydrates per hour from the first 30 minutes (do not wait until hungry)
• Run: 30 to 60 g carbohydrates per hour, gel every 30 to 40 min depending on tolerance
• Never skip 2 consecutive aid stations, regardless of how you feel
• Always carry 1 'emergency' gel in your pocket or armpit in case an aid station is missed or unpalatable

Why your gut needs training

During intense effort, blood flow is redirected toward muscles. The digestive tract receives up to 80% less blood, slowing gastric emptying. Concentrated gels, if the gut isn't accustomed to them, cause nausea, bloating, or diarrhea.

Gut training protocol:

• Consume race nutrition (gels, drinks, bars) DURING your long training sessions, not only in competition.
• Gradually increase concentration over 6 to 8 weeks.
• Test your complete nutrition plan (quantities + brands) on at least 2 long sessions before the race.
• Avoid new products in the 3 weeks before the event.

What you will find on the course

Ironman courses typically offer isotonic gels from the partner brand, water, energy drinks, bananas, cola (often from the last 30 km of the run) and sometimes salted crackers. The exact list is published in the athlete guide 4 to 6 weeks before the race. Read it. Products change from one edition to another and from one location to another.

Key note: provided gels are almost always isotonic (to be taken without extra water). If you take the gel and also drink water, you dilute it and slow absorption. Read the brand instructions.

The golden rule: test before or do not use

If your nutrition plan uses gels from one brand and aid stations stock another, you have two options: (1) carry all your nutrition (heavier, simpler mentally); (2) incorporate the provided products into your preparation from 6 to 8 weeks before the race.

Never mix the two without testing them together. Combining isotonic gel with isotonic drink often delivers too much fructose simultaneously, which is the recipe for GI distress. Cola in the late run is nearly universal (fast carbs, caffeine, salt, psychological boost). Test it 1 to 2 times on your long run 3 to 4 weeks before the race.

Dehydration vs hyponatraemia: two opposite threats

Dehydration reduces plasma volume, raises heart rate and degrades cognitive performance. A loss of 2% of body weight already causes a measurable performance drop. But hyponatraemia (blood sodium too low) is more insidious: it occurs when you drink large quantities of plain water without compensating with sodium, diluting the plasma.

Initial symptoms are similar (nausea, fatigue, confusion), but treatments are opposite: salt for hyponatraemia, water for dehydration. During a race, a diagnostic error can be fatal. Prevention through an adequate sodium-water strategy is the only real solution.

Calculating sodium needs during exercise

Sweat contains between 400 and 1800 mg of sodium per litre depending on the individual. 'Salty sweaters' (very salty sweat, white stains on jerseys) have significantly higher needs. A sweat test in a laboratory or via a wearable gives a precise estimate, but a practical approach is to note whether you have frequent cramps or intense salt cravings during a race.

General target in hot conditions: 700 to 1000 mg of sodium per hour of effort. Gels provide approximately 50 to 150 mg per unit. Supplement with electrolyte tablets (check labels: prefer those based on sodium chloride, not potassium alone). Commercial isotonic drinks generally provide 400 to 600 mg/litre.

Practical protocol for a race in high heat

Before the race: moderate hyperhydration (500 ml of water with electrolytes 90 minutes before the start, no more to avoid diluting sodium). On the bike: 500 to 750 ml of liquid per hour, adjusted for conditions. Do not exceed 1 litre/hour unless your tested sweat rate justifies it.

On the run: use aid stations methodically. Water on the head and neck to cool, isotonic drink for hydration. If you have nausea and have drunk a lot of water, take salt first before continuing to drink. Report any symptoms of confusion, severe headaches or visible oedema to medical staff.

Why glycogen is the limiting factor in long-distance

Glycogen is the storage form of carbohydrates in muscles and liver. At moderate to high intensity (zone 2 to zone 4), muscles primarily consume glycogen. Total stores in a trained athlete amount to approximately 400 to 600 g of glycogen, representing 1600 to 2400 kcal - or 2 to 4 hours of effort depending on intensity.

Over an Ironman lasting 9 to 14 hours, you cannot empty your stores without replenishing them by eating during the race. But a maximal starting reserve slows this depletion and reduces the risk of bonking - the moment when liver glycogen is exhausted and performance drops sharply. Carbohydrate loading can increase initial stores by 20 to 30 percent.

The J-3 to J-1 protocol: how and how much

J-3 (three days before): begin increasing the proportion of carbohydrates in your diet. Aim for 7 to 10 g of carbohydrates per kilogram of body weight per day. For a 70 kg athlete, this means 490 to 700 g of carbohydrates per day - approximately 2000 to 2800 kcal in carbohydrates alone.

Recommended sources: white rice (easy to digest), white pasta, white bread, potatoes, bananas, oat flakes, rice pudding. Avoid excess fibre (legumes, large amounts of raw vegetables, wholemeal bread) which can cause digestive discomfort on race day. Reduce fats and proteins proportionally to make room for carbohydrates in total calorie intake - no need to eat more total calories than usual.

J-1 evening and race morning

The evening before: a simple, familiar carbohydrate meal, finished 3 to 4 hours before your bedtime. Avoid new foods, large amounts of tomato sauce (acidity), raw vegetables and excess protein. A good option: white rice plus grilled chicken plus a little olive oil plus a banana. This is not the time to experiment.

Race morning: eat 3 to 4 hours before the start. A breakfast rich in easy-to-digest carbohydrates (white bread plus jam, oat flakes, salted white rice, sliced bread plus honey) with 500 ml of water. No fibre, no fat, no large amounts of milk. You had 3 days to fill up - race morning is mainly to replenish liver glycogen consumed overnight, not for a final major load.

The 60 to 90 g carbohydrates per hour rule

The intestine can absorb a maximum of 60 g of glucose per hour via its SGLT1 transporters. Exceeding this limit without specific training causes gastrointestinal issues (nausea, diarrhoea, abdominal cramps) - the number one cause of DNF on Ironman. By combining glucose and fructose (2:1 ratio), you can reach up to 90 g/h because fructose uses different transporters (GLUT5). This is the principle of maltodextrin + fructose gels.

Beginner (first 70.3 or Ironman): target 60 g/h on the bike, 45 g/h on the run. Elite: up to 90 g/h if the gut has been trained. Golden rules: start consuming after 30 minutes of cycling, not before (effort alone does not yet deplete reserves). NEVER change products on race day - use exactly what you have used in training.

Concrete timing on a 70.3 (bike 2h30 + run 1h40)

Bike (target 60 g/h): first intake at 25-30 min, then every 20 to 25 min. One standard gel (22-25 g) + one sip of energy drink (20-25 g) per intake. Extra water at each aid station to help gel digestion. Optional solid bar at mid-course if gut tolerates it well.

Run (target 45 g/h): gel at 15 min, gel at 45 min, gel at 75 min if your run exceeds 1h30. At each aid station: water or drink depending on heat. Avoid overly concentrated drinks if hot (slow gastric emptying). On a full Ironman, add sodium (500 to 700 mg/h in heat) to prevent hyponatraemia - a common cause of late-race collapse on Ironman.

The fundamentals of hydration

The standard recommendation is to drink 500 to 750 ml per hour during moderate to high intensity effort in warm weather. These figures vary greatly depending on individual sweating rates (from 0.5 to 2 L/h depending on athletes and conditions). The only way to know your rate is to weigh yourself before and after a 1-hour effort without drinking, in race-similar conditions.

Losing 2% of body weight in water causes a measurable performance drop. At 3%, the risk of cramps and heat stroke increases. The goal is not to compensate exactly (possible overhydration) but to stay within a reasonable window.

Bike segment: when and how much

Cycling is the main hydration window in triathlon for two reasons: you are in a stable position with easy access to bottles, and you have more gastric capacity than when running.

Simple protocol: 1 bottle of 750 ml every 60 minutes in normal conditions (under 25 degrees), 1 bottle every 45 minutes in strong heat (over 30 degrees). Prepare bottle 1 with water and electrolytes, bottle 2 with plain water. Alternate between the two on long distances. Drinking small and regularly (every 15-20 min) is more effective than drinking a lot at once.

Run segment and warning signals

In the run, the ability to absorb liquids is reduced (stomach engaged, more intense effort). Goal: maintain the level achieved on the bike, not catch up a deficit.

At aid stations: never skip a station when it is hot. Pour 1 cup of water over your head (cooling), drink 1 cup of water or isotonic drink.

Warning signals: very dark urine = serious dehydration. No urge to urinate after 2 hours of effort = strong signal. Severe headaches and nausea = potential heat stroke: slow down and seek help.

State of reserves at the start of the run

After 4 to 6 hours of cycling on an Ironman, glycogen stores are significantly depleted even with perfect bike nutrition. You need to continue providing carbohydrates on the run to maintain performance, but your gastric capacity and tolerance are reduced.

Nausea on the run is the most common signal of overfeeding on the bike (too many gels, too high concentrations). If you feel nausea in T2: water only, no gel until improvement.

Target carbohydrates on Ironman run: 40 to 60g per hour (versus 60 to 90g/h possible on the bike). The hotter it is, the more priority goes to hydration.

What to consume on the run

Isotonic gels: standard format in Ironman racing. Take every 30 to 40 minutes with 150 to 200 ml water. No more than 2 different brands in the same race (risk of incompatible blends for your gut).

Isotonic drinks at aid stations: absorbable instead of gels if your gut tolerates gels poorly when running. Less concentrated, better tolerated. Check composition in advance.

Vegetable or chicken broth: available in the second half of the run on many Ironman courses. Sodium and salty flavour that helps nauseated athletes who can no longer tolerate sugar. Very effective in the last km if the stomach rejects everything sweet.

Cola (Coca-Cola): available on almost all Ironman courses after km 20 to 25. Sugar and caffeine that help some rebellious stomachs. Use in small quantities (half a cup) with water.

Warning signals and real-time management

Persistent nausea: return to water only for 1 to 2 km, then try a quarter gel with water if the urge returns. Do not force intake if your body actively refuses. Moderate hypoglycaemia for 15 min is better than vomiting followed by zero absorption for 45 min.

Energy wall (glycogen crash): sudden drop in strength and clarity, lead-weight legs, concentration trouble. If you feel it coming: walk immediately and take rapid sugar (sweet gel, cola). Running through it worsens the phenomenon. Recovery takes 15 to 25 minutes after carbohydrate intake.

Overheating: if you start feeling cold in heat, trembling, or no longer knowing where you are: possible heat stroke. Stop, call for help, wet the whole body. This is not ordinary fatigue.

Sodium: the central electrolyte

Sodium is the electrolyte lost in greatest quantity in sweat (500 to 1500 mg/h depending on sweat profile). It is critical for maintaining water balance, muscle contraction and nerve function.

Race requirements: 500 to 1000 mg of sodium per hour is a common target for an Ironman in hot weather. 'Heavy sweaters' (abundant sweat, white marks on clothing) can go up to 1500 mg/h.

Race sources: salted gels (100-200 mg per gel), isotonic drinks (300-500 mg/500ml), salt capsules (200-500 mg per capsule). Do not rely solely on carbohydrates for sodium intake: classic gels contain very little.

Deficiency sign: muscle cramps, weakness sensation without obvious cardiac cause, nausea. To distinguish from hyponatraemia (too much water without enough salt) whose symptoms are similar but whose cause is opposite.

Potassium and magnesium: roles and sources

Potassium: plays a key role in muscle contraction and cardiac rhythm regulation. Lost in sweat but in smaller quantities than sodium (150 to 500 mg/h). Most sports drinks contain an adequate dose (100-200 mg/500ml). Natural sources: bananas (422 mg), dates (668 mg per 100g), orange (237 mg).

Magnesium: involved in over 300 enzymatic reactions, including ATP synthesis and muscle relaxation. Deficiency often responsible for nocturnal cramps and muscle cramps at end of race. Race sources: some gels and drinks contain it. Preventive supplementation: 300-400 mg/day of magnesium bisglycinate in pre-competition weeks can reduce cramp susceptibility.

Emergency supplement during race: a gel or 'electrolyte complex' capsule containing all 3 minerals (sodium + potassium + magnesium) is practical to carry in the bike kit or running belt.

Practical electrolyte management strategy

Before race: do not overload on plain water (risk of dilutional hyponatraemia). Drink salty water or an isotonic drink in the 2 hours before the start. Consume a sodium-rich meal the evening before (pasta with salt, not a bland diet).

Bike: salt capsules every 45 to 60 minutes in addition to gels and drinks. Drink according to thirst, not on a fixed schedule. In heat, increase the sodium dose.

Run: if stomach tolerates, continue salt capsules at aid stations, alternate water and isotonic drinks. If sudden cramps occur, stop for 30 seconds, stretch, take a salt capsule and drink a few sips of water.

Training test: never try a new electrolyte protocol in a race. Test in real conditions (4h cycling session in hot weather) to calibrate your personal needs.

The evening meal before a morning long session

Principle: maximise muscular and hepatic glycogen storage so it is available the following morning. Glycogen stores of a trained athlete are approximately 400 to 600g (1600 to 2400 kcal), but they deplete in 60 to 90 minutes of intense effort if not compensated.

Ideal composition for J-1 dinner: 60-70% medium to low glycaemic index carbohydrates (brown rice, al dente pasta, quinoa, boiled potatoes), 20-25% protein (chicken, fish, egg), 10-15% fat. Avoid excess saturated fat (fatty beef, full-fat cheeses), large amounts of fibre (legumes, large portions of raw vegetables), and alcohol (inhibits glycogen resynthesis).

Quantity: long session the next day (3h or more) = increase carbohydrate volume by 15-20% vs your typical dinner. Moderate session (1h30-2h): usual meal is sufficient.

Breakfast on the morning of the session

Ideal timing: 2 to 3 hours before the start of the session. The stomach has had time to digest and blood glucose is stable. If you can only eat 60 minutes before (very early wake-ups), opt for a very light and easily digestible meal.

Composition 2-3h before: 60-80g carbohydrates (1 bowl of oats + 1 banana + 1 tablespoon of honey, or 2 slices of white bread + jam + 1 banana). 15-20g protein (eggs, Greek yoghurt). Very little fat (avoid large amounts of avocado, oil, cheese): fats slow gastric emptying and can cause gastrointestinal discomfort during exercise.

If less than 60 minutes before: 1 banana + 1 energy gel or 1 bar of 40-50g easily digestible carbohydrates. Never try anything new on the day of a race simulation session.

Morning hydration: 400 to 600ml of water in the 2 hours before the session, including 250ml with the meal and 250ml 30 minutes before.

Adapting to sessions and lifestyle

Fasted or semi-fasted session (advanced technique): some athletes do zone 1-2 sessions of 60 to 90 minutes fasted to train metabolic adaptations (lipid utilisation). Acceptable only for LIGHT sessions. For a long or intensive session, training fasted beyond 90 minutes almost systematically leads to bonking and muscle catabolism.

Very early morning session (5h30-6h) without the possibility of eating 2h before: option A = wake up 30 minutes earlier and eat 1 banana + 1 gel 30 minutes before. Option B = the first 30 minutes of the session in very low zone 1, then progressively increase intensity once digestion is complete.

Adapting to session duration: less than 1h30 = usual dinner, 1 banana in the morning is enough. 1h30 to 2h30 = carbohydrate-rich dinner + complete breakfast. More than 2h30 = all protocol above + start in-session nutrition at 45 min (minimum 60g carbohydrates per hour).

Mechanism and effective dosage

Caffeine acts primarily by blocking adenosine receptors (adenosine is the molecule that signals fatigue to the brain). The result: reduced perceived effort, maintained alertness, and for some athletes, improved muscle contraction.

Proven effective dosage: 3 to 6 mg per kg of body weight. For a 70kg athlete: 210 to 420mg. One espresso cup = 60 to 80mg. A standard caffeine gel = 50 to 75mg. An energy drink can = 80 to 160mg. Beyond 6mg/kg, benefits do not amplify but gastrointestinal risks increase strongly.

Timing of intake: caffeine reaches its maximum plasma concentration 45 to 60 minutes after ingestion and remains effective for 3 to 5 hours. For a race starting at 7h00, optimal intake between 6h00 and 6h15.

Practical protocol in competition and training

Half Ironman strategy (4h to 5h30): initial intake H-1 (coffee or caffeine gel, 100 to 200mg), then 1 caffeine gel every 45 to 60 min on the bike, stop caffeine gels at run km 5-10 to avoid the crash.

Full Ironman strategy (9h to 14h): initial intake H-1 (100 to 150mg only, not full dose), mid-intake at bike km 60-90 (75mg caffeine gel), final intake at run km 25-30 (75mg caffeine gel or cola at aid stations). This 'low dose repeated' strategy maintains the effect without crash and without accumulation that disrupts the following night's sleep.

Mandatory training test: before using caffeine in competition, test your dose and timing on 2 to 3 long sessions. Some athletes have gastrointestinal reactions (nausea, cramps) or palpitations at high doses. There is no universally safe protocol. What works for your training partner may not work for you.

Minimum washout period: if you are a daily caffeine consumer (coffee, tea, soda), reduce or stop 5 to 7 days before competition to amplify the race effect. Even if uncomfortable (headaches days 2-4), the competition effect will be significantly more pronounced.

Calculating water needs over 180 km of cycling

Average sweat rate: between 500 mL and 2 L per hour depending on temperature, humidity, and the individual. The majority of athletes lose between 800 mL and 1.2 L per hour in race conditions (20-25 degrees). Over 5h of Ironman cycling: 4 to 6 L of potential water loss.

The goal is not to replace 100% of perspiration (impossible) but to limit loss to less than 2% of body weight. For a 70 kg athlete: do not exceed 1.4 kg loss over 5h of cycling. In practice: drink between 500 and 750 mL per hour (2.5 to 3.75 L over 5h).

Personal calibration: the only way to know your sweat rate is to weigh yourself before and after a 1h session without drinking. Every 1 kg of loss = 1 L of perspiration. This varies with heat (double the measurement in summer compared to winter).

Sodium and electrolytes: why water alone is not enough

Perspiration contains sodium (salt). Drinking pure water for several hours dilutes blood sodium (hyponatraemia). Below 135 mmol/L of blood sodium, first symptoms appear: nausea, headaches, confusion. Severe cases can progress to coma. Hyponatraemia is more common in slower athletes (more time on course) who drink a lot of pure water at aid stations.

Solution: pair salted drink or sodium-containing gels with each intake. Recommended sodium concentration: 500 to 1000 mg of sodium per litre of drink. Commercial isotonic drinks fall within this range.

Timing: drink every 15 to 20 minutes on the bike, not when you feel thirsty. Thirst is a late indicator. Set an alert on your bike computer if necessary. The first bottle (first 45 minutes) should contain your highest sodium intake as this is the phase where you sweat the hardest.

Why 60 to 90 g of carbohydrates per hour and not more, not less

The human intestine can oxidise a maximum of 60 g/h of glucose alone. If you consume only glucose or maltodextrin, cap at 60 g/h: the excess is not absorbed and causes gastrointestinal problems (diarrhoea, nausea).

The combination of glucose + fructose (2:1 ratio) allows reaching 90 g/h because the two sugars use different intestinal transporters (SGLT1 for glucose, GLUT5 for fructose). Most modern gels use this ratio. Read the ingredients: if you see 'glucose' + 'fructose' or 'maltodextrin' + 'fructose', you are in the right ratio.

PRACTICAL CONSEQUENCE: for a 5h30 Ironman bike leg, this means between 330 g (60 g/h) and 495 g (90 g/h) of carbohydrates in total. A standard gel provides 22-25 g, a bar 30-40 g, 500 ml of isotonic drink 30-40 g. Plan your intake before the race, not by improvising.

Training the gut: the often-forgotten part

The gut trains like muscles. Triathletes unused to eating on the bike often experience nausea from the 2nd hour when attempting to consume 70-80 g/h in a race. The solution: progressively train the gut to absorb these quantities during training sessions.

GUT TRAINING PROTOCOL: during all your long bike rides of more than 90 minutes, consume exactly the same amount of carbohydrates per hour as planned in the race. Do not skip a dose because 'you are not hungry'. The objective is intestinal adaptation, not fuelling the session.

WARNING SIGNALS TO ADDRESS BEFORE THE RACE: nausea during the session, urge to vomit beyond the 3rd hour, bloated stomach after gel intake. These symptoms indicate either an inappropriate glucose/fructose ratio, or too high a concentration (drink too concentrated relative to water consumed), or an allergy to a specific ingredient. Test several gel brands during your preparation, not only those that will be distributed in the race.

The digestive context of the Ironman marathon

After 7-9 hours of cycling and fuelling, your digestive system is tired. Intestinal transit slows under the effect of heat and prolonged effort. The carbohydrate absorption window narrows. What you eat in the last 2 hours of cycling arrives at maturity at the start of the marathon: plan accordingly.

Dehydration can rapidly deteriorate the digestive situation: 3% of body weight lost in water = risk of nausea, abdominal cramps and inability to ingest carbohydrates. Monitor your urine colour at aid stations (pale yellow = well hydrated, dark yellow = deficit).

What goes down and what doesn't

GOES DOWN WELL: cola (caffeine + simple carbs + anti-nausea effervescence), vegetable broth (sodium + potassium + water), fruit (orange, banana, melon if available), liquid gels in small doses (20-25 g of carbs every 20-30 min).

GENERALLY NO LONGER WORKS: solid energy bars (too slow to digest), dairy products, dried fruit, chewing gum. Gels with high BCAA or caffeine concentration can cause nausea in sensitive people.

IRONMAN AID STATIONS: at a major Ironman, aid stations are spaced 1-2 km apart. Walk systematically at every aid station even if you're still running well: this allows you to ingest properly and bring your heart rate down 10-15 bpm.

Why you still dehydrate in cold weather

BREATHING CONSUMES WATER: in cold air, each exhalation expels air saturated with water vapour. Over 2 hours of cycling or running at 5 degrees, respiratory water loss can reach 500-800 ml - without visible sweating.

THIRST SENSATION IS BLOCKED: cold inhibits anti-diuretic hormone (ADH) and increases urine production (cold diuresis). You urinate more, but don't feel thirsty. This mechanism can cause moderate dehydration (1-2%) without any bodily alert.

PERFORMANCE AND INJURIES: 2% dehydration reduces performance by 5-8% and increases tendon rigidity (tendinopathy risk). In winter, tendon injuries increase precisely because athletes hydrate less.

Practical hydration rules in cold weather

BASIC RULE: hydrate on a scheduled basis, not by thirst. Below 10 degrees: minimum 400-500 ml per hour (vs 600-800 ml in hot weather). Since the thirst signal is inhibited, waiting to feel it before drinking = guaranteed dehydration.

CONTENT: in winter, warm or lukewarm water is sometimes better tolerated than cold water (faster digestion, better gastric tolerance). A warm isotonic drink with electrolytes also compensates for sodium loss through breathing and cold diuresis.

WARNING SIGNALS: dark urine on returning from a session = moderate dehydration. Headaches in early evening after a cold session = dehydration. Nocturnal cramps after a winter effort = electrolyte deficit. In all these cases, 500 ml of water with a pinch of salt corrects the situation in 30 minutes.

Overall target: 60-90 g carbohydrate per hour

The gut can absorb 60 g/h (glucose only) or up to 90 g/h (glucose + fructose 2:1 blend). Beyond that, the surplus ferments and causes GI issues.

For a 70 kg athlete targeting 11h: estimated energy need is 650-800 kcal/h on average. Fat provides 30-40% of that need. So carbs must provide 400-500 kcal/h, theoretically 100-125 g/h - BUT the gut can't keep up. Realistic target: 75-90 g/h with mixed products (maltodextrin + fructose).

Swim (3.8 km, 55 min to 1h30)

No nutrition during the swim. Eat a solid meal 2h30-3h before start (rice or oats + moderate protein + little fat). Avoid fibre. Drink 500 mL water or electrolyte drink in the hour before start.

Bike (180 km, 4h30 to 6h)

This is where 80% of your nutrition plays out. Target: 75-90 g carbs/h via isotonic drink + gels + bars. First hour: limit to 60 g/h (gut is just coming out of the swim). Gradually increase.

Electrolytes: 600-1000 mg sodium per hour depending on heat and sweat rate. A salt deficit is the number-one cause of cramps at the end of the bike and on the marathon.

Solids: possible up to km 120. After that, switch to liquids and gels only (the stomach struggles with solids late on the bike if intensity rises).

Run (42 km, 3h30 to 6h)

Reduce intake to 40-60 g carbs/h (digestive system is tired). Prefer liquid gels, cola at aid stations (double effect: carbs + caffeine), fruit. Drink at EVERY aid station, alternate water and isotonic.

Caffeine: 1-2 mg/kg from marathon km 20-25. For 70 kg, that's 70-140 mg (1-2 caffeinated gels or 1 cola). Don't start caffeine before that: risk of crash late in the run.

Why 60-80 g/h and not less

Hepatic and muscular glycogen storage is limited: ~500 g total for a 70 kg athlete = ~2000 kcal, or 3-4 h of Z2 cycling. Beyond that, the body seeks energy elsewhere: gluconeogenesis (liver), fatty acid oxidation, and if empty, muscle catabolism.

Providing 60-80 g of carbohydrates per hour via drink + gel + solid preserves glycogen and prevents bonk. Below 40 g/h: bonk around 3 h. Above 100 g/h: probable gut intolerance (cramps, nausea). Optimal window = 60-80 g/h, trainable up to 90 g/h with regular gut training.

How to split: liquid + solid

For 60 g/h: 30 g in the drink (500 ml at 6% carbs), 15 g in a gel, 15 g in a solid (banana, bar, rice cake). Solid food matters > 2 h: mixing textures reduces palatability fatigue and gut intolerance.

Avoid pure fructose (hepatic bonk): favour maltodextrin blends (2:1 glucose:fructose) which push intestinal absorption up to 90 g/h. Tested and digestible brands: Maurten, Precision Fuel & Hydration, SIS Beta Fuel. Home-made: maple syrup + salt + water = 60 g/h at low cost.

Nutrition training = training

Your 4 h Z2 long ride is also your nutrition training session. Repeating the same strategy 8-12 times before the race trains the digestive system to absorb 60-80 g/h without intolerance. This is training in itself, measurable: on first attempts, you will feel cramps or nausea. Over 8 rides, it improves.

Classic mistake: trying a new drink or gel on race day. Absolute rule: nothing new on race day. Your race strategy = the one you successfully replicated 8 times in a row in training, with no gut issue.

Swim: 5 essentials

1. Wetsuit: €150-300 second-hand (5 mm for water <20 °C). Neoprene gives 5-8% time gain + buoyancy = less panic. Non-negotiable in open water.
2. Clear + tinted goggles: early start = clear, sun = tinted. Brands like Aquasphere or Roka, €20-40 each.
3. Silicone cap: provided by organiser (wave colour).
4. Tri-suit: 1-piece back-zip with bib pocket. €80-200 entry level is fine.
5. Anti-fog + Vaseline (neck): €5 total but saves the race.

Bike: what ACTUALLY matters

A TT/triathlon bike is NOT mandatory. A road bike + clip-on aerobars (€40-80) gives 80% of the aero gain for 1/20th of the price. Priorities:

• Quality tubeless tyres (GP5000 S TR, €70-90 a pair): -5 to -10 W rolling resistance vs cheap. Real time gain.
• HR strap + power meter: a crank-based meter (4iiii, Stages) at €250-400 = step-change for pacing.
• Aero bottles + gear holder: €30-50, aero gain and autonomy.
• Tools + tube + CO2 cartridge: a puncture at km 80 without them = DNF.

Avoid: brand-new deep-section carbon wheels (€1500+) for your first IM. Aero-wise, the engine (you) is the bottleneck, not the gear.

Run: the single most important thing

One rule only: your race-day shoes must have 100-300 km on them, never brand-new. A pair of Saucony Endorphin Pro, Nike Vaporfly or Hoka Mach (€200-280) for race day, and a different "training" pair (Asics Nimbus, New Balance 880, €130-180) for long runs.

Useful accessories: visor (€10-15), gel belt (€20), anti-blister socks (€15 a pair). Total run gear < €400 is plenty.

Honest total budget

Sensible second-hand build: €1500-2500 all-in (bike + wetsuit + shoes + accessories). Brand-new entry level: €3000-4500. Beyond that, you're paying for marketing.

The real IM investment is TIME. Buying expensive gear won't shorten your 12-20 h/week training load.

Why a fit is non-negotiable in long distance

On a 70.3 or an Ironman, you spend 2.5 to 6 hours on the bike, in aero position, barely moving. A saddle 1 cm too high or too low, badly placed hoods, a stem too long → 4 h later you step off with tingling hands, locked-up neck, or a screaming knee. The marathon afterwards becomes purgatory.

Biomechanics can't be overridden by willpower. A poorly-fitted athlete loses 5-15 W at the same perceived effort, then gets injured.

What a REAL bike fit does (vs. a fake one)

A pro bike fit takes 2-3 h. The fitter measures your hip/ankle/shoulder mobility, has you pedal under sensors (Retül, Guru, or similar), and adjusts in this order:

1. Saddle height: knee extension ~30-35° at the bottom, or KOPS (knee over pedal spindle) at 0 ± 1 cm.
2. Saddle setback: aligned with the crank, tweaked for mobility.
3. Bars/hoods: height + reach based on torso and hamstring flexibility.
4. Cleats: axis + float depending on Q-factor.

The €30 "fits" at the shop that just adjust saddle height in 15 min ARE NOT a fit. They're an aesthetic adjustment.

When to go, when to return

First fit: as soon as you buy a road or TT bike, or at the latest 8-10 weeks BEFORE your first IM (so you have time to adapt to the position and ride 500-1000 km on it).

Re-fit: every 18-24 months, or after any major change (saddle, bars, hoods, aero bars, gaining/losing 5+ kg, recurring back/knee/shoulder injury).

Realistic budget: €150-€300 in France for a 2-3 h pro fit. Pricey? Compare with one post-IM physio session, or 20 W lost over 5 h. It's the best-ROI investment in the sport.

Drop: what it is, what it changes

Drop is the height difference between heel and forefoot, in millimeters. A "10-drop" shoe has 10 mm more under the heel than the toes; a "0-drop" is flat.

Mechanically, the lower the drop, the more your foot lands midfoot/forefoot → calf and Achilles tendon work more. The higher the drop, the more heel-strike happens → load travels up to the knee and hip.

Common drops: 0-4 mm (minimalist), 6-8 mm (modern standard), 10-12 mm (classic running).

Which to pick based on your history

You have a fragile Achilles or calves (past tendinopathy, recurrent calf pain) → drop ≥ 8 mm. The higher heel offloads the posterior chain.

You have fragile knees or hips (chondromalacia, IT band syndrome, hip pain) → low/medium drop 0-6 mm. You offload the front and ease quad/knee.

No history → 6-8 mm drop is the safest compromise. Avoid extremes (0 or 12) without a specific reason.

In a rotation, keep at least 2 shoes with SIMILAR drop (±2 mm). Alternating drop 4 and drop 10 every run = double load on everything.

How to switch drops WITHOUT injury

Drop switching is the #1 cause of Achilles tendinitis in amateur runners. Rule: don't change by more than 4 mm at once. To go from drop 10 to drop 4:

1. For 3-4 weeks, alternate drop 10 (long run + tempo) and drop 6-8 (short easy runs) → adaptation.
2. Then 3-4 weeks drop 6-8 on the majority of sessions.
3. Finally you can go down to drop 4.

Total: 6-8 weeks transition. Skip steps → calf/Achilles will punish you for 3 months.

When you get a new pair, do 2-3 easy 30-40 min runs BEFORE doing a long run or intervals in them.

Fit > everything else: 80% of the gain is here

A €200 wetsuit perfectly fitted easily beats a €700 one that chafes the neck or pinches the shoulders.

Shop test (or pool fitting):

1. Neck seam flat against the neck : not pinched, not gaping. If 2 fingers slip between neoprene and neck while standing, it's too wide (water ingress).
2. Arms overhead without resistance : must lift both arms fully without feeling the neoprene pull your back. Otherwise you'll be exhausted by 500 m.
3. Open armpits : no fold, no air pocket. Fold under the arm = chafing after 30 min.
4. No fold behind knees or in lower back : these create drag and chafing.

Fail even one of these 4 = wrong size. No brand, no price compensates.

Thickness and zones: what actually matters

Neoprene comes 1.5 mm to 5 mm. Manufacturers segment by zone:

• Chest / back / thighs: 4-5 mm. This is where you need buoyancy and warmth.
• Armpits / arms / shoulders: 1.5-2 mm. This is where you need MAXIMUM mobility. Too thick = scapular exhaustion.

Entry €200 wetsuits generally respect this zoning. €400-€600 ones add SCS neoprene (super composite skin) that glides better (gain ~1-3 sec / 100 m). Beyond that, pure marketing.

Special case: cold water < 16 °C → go for a 5/3 "full" wetsuit (5 mm body / 3 mm arms). Water > 22 °C → sleeveless or shorty to avoid overheating.

Legality, care, lifespan

Race legality:

• Water < 16 °C: wetsuit MANDATORY.
• 16-22 °C: wetsuit allowed (= 95% of amateur IMs).
• 22-24.5 °C: amateurs allowed, pros not.
• > 24.5 °C: BANNED for all (IM rule). Rule tightened after Kona 2014 deaths.

Care: freshwater rinse after EVERY session. Dry in shade (UV degrades neoprene). No prolonged chlorine (occasional pool OK, but cap at 10 sessions/yr unrinsed). Store flat, no coathanger (neoprene deforms).

Realistic lifespan: 3-5 years at 30-50 sessions/yr. Beyond, neoprene hardens, loses 20-30% buoyancy. You feel "heavy" without understanding → time to replace.

Criterion 1: continuous GPS battery life

An Ironman runs 9-16 h. Your watch runs GPS continuously (HR + external ANT+/Bluetooth sensors + barometric). Target a minimum of 18 h GPS battery life in standard GPS mode (not the battery-saver mode that degrades accuracy).

Verify: the manufacturer's quoted figure is for highest-accuracy GPS WITHOUT external sensors or music. With sensors (HRM, power meter, cadence), divide by 1.3-1.5. A watch advertised at 30 h gives ~22 h in real IM config.

Minimum threshold: 18 h continuous GPS, sensors on. As of 2026, almost every mid/high-end triathlon watch beats this.

Criterion 2: clean multisport mode

Multisport mode lets you switch swim → bike → run → bike → run with ONE button press, recording every transition in the same activity file.

Test in-store: start the triathlon activity, chain 5 discipline changes. If the watch lags, asks for confirmation, or loses HR at every transition → walk away. T1 on an IM lasts 3-5 min: no time to wrestle with the UI.

Useful bonus: a "long triathlon" mode that pre-configures disciplines (Swim → T1 → Bike → T2 → Run) and split times, with no setup.

Criterion 3: reliable open-water support

On 3.8 km open water, your watch needs to give a credible distance (± 5-10%), trace your line correctly on Strava/Garmin Connect post-race, and survive salt water + impacts.

3 common problems to test:

• Underwater GPS drop: the watch loses signal every arm stroke. All modern watches correct via interpolation. Test on a real 1500 m open-water session before committing to an IM.
• Optical HR in swim: 90% of optical sensors are unreliable under cold water + wetsuit. For reliable swim HR, use a chest strap (Polar H10 or equivalent) with internal memory that transfers after the swim.
• IPX8 + 50 m waterproofing: bare minimum. €200 watches are often labelled "waterproof" but die after 6 months in salt water.

Criteria 4 and 5: navigation and external sensors

Criterion 4 : GPX/route navigation: useful on an unfamiliar IM course for following the bike route (vibrate at next turn). Not critical in an official race (course is marked), critical for long training on new roads.

Criterion 5 : External sensor compatibility: ANT+ AND Bluetooth (both, not either-or). You must be able to connect: bike power meter, cadence sensor, chest strap, optional foot-pod. Verify the watch supports sport profiles "road cycling + triathlon + open-water swim" (not just "free activity").

Remember: a bike power meter (~€250 second-hand) plus an honest triathlon watch (~€400) is the highest-ROI gear investment for your first IM. The rest (wetsuit, bike, helmet) matters far less.

Why a triathlon saddle differs from a road saddle

On a road bike, you tilt slightly forward. Your pelvis sits on the saddle via the ischial tuberosities (those 2 bones you feel when sitting on a hard chair).

On a triathlon bike in aero, your pelvis ROTATES 15-30° forward. The pressure point moves from the ischia to the PUBIS (pubic bone) and perineal area. A standard road saddle applies intense PRESSURE on this area = pain, numbness, even long-term urological issues.

That's why triathlon/TT saddles have 3 distinctive features:

• Short nose (240-250 mm vs 280 mm road). Frees the pubis.
• Pronounced central cut-out or channel: offloads pressure on soft tissue.
• Wide rear platform: you naturally slide forward in aero, the wide front gives you a few cm of position tolerance.

The 3 major triathlon saddle families

1. "Split-nose" saddles : e.g. ISM, Cobb, BiSaddle: The nose is SPLIT into 2 parallel prongs with a central gap. Zero perineal pressure. Very popular with long-distance pro triathletes. Downside: visually "weird", requires adaptation for newcomers (the first 2-3 rides may surprise). Price: €130-200 new.

2. Classic "short-nose" with cutout : e.g. Specialized Power, Fizik Argo, Selle Italia SLR Boost: More traditional shape, but truncated nose and wide central cutout. More versatile (usable in road position when sitting up), great comfort for most amateurs. Cross-brand best-seller. Price: €100-250 by rail type (steel / titanium / carbon).

3. Wide flat front-platform saddles : e.g. Profile Design Tritri, Adamo Time Trial: Very short nose and very wide "table-like" front platform. Ideal for very extreme aero positions (elite TT, Olympic TT). Possible discomfort with moderate aero positions (you slide on the platform without reference). Price: €100-180.

Remember: 80% of amateur IM-ers find their fit in family 1 (split-nose) or 2 (classic short-nose). Family 3 is more specialised.

How to choose YOURS

Step 1 : Know your sit-bone width: most Specialized / Trek / Bontrager shops have a measurement pad. Typical width: 110-140 mm. The saddle should be 20-30 mm wider than that measurement (to comfortably support the ischia).

Step 2 : Mandatory trial period: most good high-end saddles can be rented or tested (Specialized Body Geometry program, manufacturer programs, or triathlon clubs with a saddle "library"). DO NOT buy blind. 30-60 day trials sometimes offered.

Step 3 : Dynamic bike fit: if you can afford 1 thing all season, it's a bike fit (€90-150). The pro measures your aero position with sensors (knees, hips, back) and tunes saddle height/setback/tilt to the mm. A perfect saddle badly positioned hurts as much as an average saddle well positioned.

Step 4 : Real-condition test: 2 rides of 3-4 h before judging. The first 30-60 min, any new saddle is uncomfortable (different pressure zones). The verdict comes after 2-3 h on a long ride.

Signs a saddle suits you:

• You can stay 3 h in aero without exiting the bars.
• No perineal numbness ("tingling" below).
• You don't need to stand up 2× per 10 km.
• The next day, ischia ache a bit but zero central pain.

The TT aero gain: real but conditional

Over an Ironman 180 km at an average speed of 34-38 km/h, air resistance accounts for 70-80% of the total power required. A well-positioned TT bike can reduce CdA (drag coefficient × frontal area) by 15-25% compared to a road bike in a standard position. In time terms: 8-15 minutes saved on an IM bike, per studies by Fintelman et al. (2015) and wind tunnel data from brands like Cervélo, Trek and Canyon.

But : and this is the crucial point : these gains are conditional on correctly holding the aero position throughout the entire race. A poorly fitted TT position or one the athlete "gives up" mid-race (too painful, lower back giving out) can cost more than it saves:

• Abandoned aero position = CdA identical to a road bike → zero gain
• Position that compromises run stride (lack of hip flexor mobility on TT) → can cost 2-3 min on the IM marathon

The road bike: underrated for early triathlon

A modern road bike with an aggressive position (short stem, low bars) and profiled wheels provides 60-70% of the aero gains of a dedicated TT bike for 30-40% of the cost. For a beginner triathlete or in a base-building phase, the road bike advantages are concrete:

Long-duration comfort: over 5-6h of IM biking, position comfort directly impacts your ability to run afterwards. A well-fitted road bike lets you stretch, change position, relieve your lower back : impossible on a strict TT.

Training versatility: group rides, peloton racing, cycling in bad weather, long mountain rides : all better on a road bike. A TT used 80% of the time solo on flat courses is optimal; in varied conditions, you lose the benefits.

Maintenance and adjustment: the TT often has a more complex drivetrain, less tolerant geometry to minor adjustments, and tri extensions (aero bars) require specialist fitting. A bad TT fitting on an IM can cause neck pain or hand numbness.

Practical rule: if you have fewer than 2 triathlon seasons and do 70.3 (where the bike only lasts 2h-2h30), stay on the road bike. The TT is clearly justified for Full IM after a season of practice and if you have access to a qualified fitter.

The middle option: aero bars on a road bike

If you want aero benefits without investing in a dedicated TT, adding clip-on aero bars to a road bike is the solution favoured by many amateur triathletes. Cost: €50-150 for quality clip-ons (Profile Design, Vision). Gains: 5-10 min on an IM depending on position adopted, i.e. 50-70% of a real TT's gains.

Regulatory note: in races, aero bars are allowed in non-drafting events (most mass-participation IM and 70.3). They are banned in draft zones (some Olympic triathlon, junior events, specific races). Check the rules before fitting extensions.

Physical restriction: aero bars on a road bike create a low back and closed hip position that loads the lower back differently from a TT. If you're not used to it, start with short sessions (30-45 min) in aero position before spending several hours there.

Decision criteria: road, aero bars, or dedicated TT?

What matters more than the bike: your FTP, ability to hold target intensity for 5-6h, and your training bricks. A well-trained athlete on a road bike will outpace an underprepared athlete on a €10,000 TT. The bike is the last lever to optimise, not the first.

Rim depth: which profile for which use

Rim height (in mm) determines aerodynamics and crosswind stability. It's not a brand decision : it's primarily a terrain and skill decision.

Common profiles and recommended use:

• 25-35 mm (low profile): all-terrain, climbs, strong winds, beginners. Little aero effect but very stable. Ideal for triathlons with significant elevation (Vichy, Embrunman).
• 45-50 mm (medium profile): best compromise for most LD triathlons on semi-flat terrain. Measurable aero gain without becoming unmanageable in gusts.
• 60-80 mm (deep profile, 'deep clincher' or 'race wheel'): flat terrain, moderate crosswind, experienced athletes. Every 1 km/h of crosswind demands more steering effort. In a 70.3 with 20 km/h side wind, an inexperienced athlete can lose more time to trajectory corrections than the aero watts gained.
• Disc wheel (rear): reserved for professionals and athletes on flat, wind-free courses. Banned at some races in high wind conditions.

The amateur rule of thumb: if you can make your bike tip sideways by rocking on it at a standstill with a wheel > 60 mm, it's too deep for you on a windy day.

Carbon vs aluminium wheels: the real trade-off

Carbon isn't mandatory to be fast : it's a question of budget and context.

Aluminium:

• Price: €100-400 per pair for decent quality.
• Lateral stiffness often better than entry-level carbon.
• Consistent braking in both dry and wet conditions (alu rim = stable braking surface).
• More accessible repair in case of crack or impact.
• Weight: 1,700-2,000 g per pair.

Carbon:

• Price: €500-4,000+ depending on brand and depth.
• Weight saving: 300-600 g vs good alu : felt most on climbs.
• Better aero at equivalent depth thanks to toroidal profile (teardrop rim cross-section).
• Requires specific carbon brake pads (NEVER alu pads on carbon rims: guaranteed destruction). In rain, carbon braking degrades : anticipate on descents.
• Heat warning: long descents with repeated braking = rim temperature rise → deformation of tubular/tubeless tyre. Cool the rim with water before re-entering hairpins.

Verdict for an amateur doing their first IM: start with good profiled alu wheels (35-45 mm). Carbon gains are real but secondary if position, power and nutrition are still being optimised.

Fitting and maintaining your wheels: mistakes to avoid

Before each ride or race:

• Check pressure according to tyre type and your weight. Tubeless 700x25: 5-6 bar for 75 kg, 4.5-5.5 bar for 60 kg. Tubular: 7-8 bar. Use a floor pump with a gauge, not a frame pump without one.
• Check for cuts or embedded debris in the tyre. Often invisible but puncture-inducing under pressure.
• Inspect spokes: a broken spoke = buckled wheel = asymmetric braking = danger.

Fitting a tubeless tyre:

1. Mount the tyre dry first, no sealant : check it seats properly on the hooks.
2. Inject sealant (30-60 ml depending on brand) through the valve.
3. Inflate progressively (floor pump with tank or CO2 inflator) until you hear the beads click into place.
4. Spin the wheel in all directions to distribute the sealant.
5. Check for leaks 24 h later before riding.

Winter maintenance:

• Wipe rims with a dry cloth after every wet ride. No direct water jet on hubs or bearings.
• Check rear tread wear (disappearing centre groove = change the tyre before your race).
• Renew tubeless sealant every 3-6 months (it solidifies).