The 4-week comeback after a sick week.

You missed a week to a chest cold. The plan was supposed to peak in seven. There is a real four-week protocol for this, the same one elite coaches hand their athletes when illness lands in the middle of a build. Sourced from Friel and the illness research.

You felt it coming on Sunday night. Tuesday you tried a Z2 spin and your HR ran 20 bpm high. Wednesday the cough settled in. Thursday and Friday were the couch. Saturday felt almost normal but not quite. Now it is Monday again, six days into a build cycle that was supposed to peak in seven weeks.

The wrong move is to try to make up the week. The other wrong move is to write off the cycle. There is a real protocol for this exact thing, and it is the same protocol elite coaches hand their athletes when they catch a chest cold three weeks out from a goal race.

This article is what we hand to every solo athlete on TriPaced after a sick week. Four weeks. Not back to normal in three days. Not skip the rest of the build. A real plan that gets you back to where you were, without breaking what you have.

Why most plans punish you for getting sick

Most amateur 70.3 and Ironman plans treat illness as a gap. The week becomes a hole in the chart. Then the plan resumes at exactly the volume and intensity it would have prescribed if the gap was not there. You feel weak. You push the long ride. The Wednesday tempo lands degraded. Two weeks later, something else gives.

The math is unforgiving here. In the Banister fitness/fatigue model (Banister, 1991), a missed week drops your fitness (the 42-day exponential moving average) very little. But your fatigue (the 7-day one) drops almost completely. When you come back, your TSB (training stress balance) is artificially high. You feel rested. The plan still prescribes the volume that matched the old you. You inhale that volume and ride straight into a fatigue crash three or four days later. Coaches call this the comeback bonk. It is preventable.

The real cost of a sick week is not the week. It is the wrong response to the week.

The first decision: how long were you really out?

Before you reach for a protocol, count honestly. There is a difference between I was sleeping more than usual but trained light and I lay on the couch for five days.

The neck check (Watson, 2017). Symptoms above the neck (runny nose, sore throat, mild headache) generally tolerate easy aerobic work at 60 percent of normal intensity. Symptoms below the neck (chest cough, fever, body aches, GI distress) are a hard stop. You do not train through them. The research is clear: training with a febrile illness raises the risk of viral myocarditis, an injury we never recover the same year from.

Count the actual zero days. If you trained at 50 percent load three days that week and skipped two, you missed two equivalent days. If you skipped five fully, you missed five. Five zero days is a different animal than two.

Track resting HR. Elevated resting HR for more than two days post-symptoms is the immune system still cleaning up. Friel covers this in The Triathlete's Training Bible (5th ed., 2024): when morning HR runs more than 8 bpm above your baseline, the body has not finished the job. Pushing on top of that is what extends the cold into bronchitis.

Honest count first. Protocol second.

Week 1 — return to easy work

For a five-day-out illness, week 1 is not training. It is re-introducing motion. The goal is to circulate, restore neuromuscular feel, and signal to your nervous system that the streak survives. The goal is not adaptation.

Volume: 50 to 60 percent of pre-illness volume. If you were riding 6 hours, you ride 3 hours and change. If you were running 4 hours, you run 2 and a quarter. Spread across more sessions of shorter duration, not fewer long ones.

Intensity: Zone 1 to easy Zone 2. No tempo. No threshold. No race-pace efforts. Friel's three-hour rule still holds: a sub-three-hour aerobic session moves nothing on your fitness curve in either direction, so it is the safest carrier for show-up work that costs almost nothing.

Discipline mix: Reintroduce swim and bike first. Running comes back last. Running carries the highest neuromuscular and orthopedic risk after a layoff, and the post-illness body has lost specific running readiness faster than it lost aerobic capacity.

The morning warnings check (Friel's term, our translation): every morning of week 1, score your recovery 1 to 10 before you decide on the day. Below a 6, you halve the prescribed session and replace structure with easy aerobic. Above a 7, you proceed as planned.

End of week 1: you should feel almost normal. If you do not, week 2 is a repeat of week 1, and we extend the protocol to five weeks total. Honesty over ambition.

Week 2 — re-introducing intensity, carefully

This is the week most amateur plans break. The athlete feels good. The watch says HR is back to baseline. The plan prescribes a full threshold set. The athlete buries it. By Saturday they are wrecked.

The correct move is signal without dose.

Volume: 75 to 80 percent of pre-illness. You add back duration, not intensity.

Intensity: One quality session per discipline. Just one. And it is half volume at correct intensity. A four-by-five-minute threshold becomes two-by-five. A long run with race-pace surges becomes a long run with two surges. The adaptation we want is the body re-learning to recruit and clear lactate, not a maximum dose of either.

The rationale is dose-dependence, a principle Coggan and Allen lean on in Training and Racing with a Power Meter: the adaptive signal is highest in the first half of any quality session. After that you are mostly stacking fatigue. After a layoff you do not need more fatigue. You need the signal.

Long sessions: the long swim and long ride return at full duration, but at the easy end of their normal intensity. The long run stays 25 percent below pre-illness duration.

Anchor check: if any session leaves you wrecked for more than 24 hours, you scaled wrong. Drop back to week 1 protocol for two days and re-enter.

Week 3 — full volume, conservative intensity

By week 3 you should feel like yourself with a thin layer of rust still on the high end.

Volume: 100 percent of pre-illness. Long sessions back at their full duration.

Intensity: Quality sessions return to full volume but at the lower end of their normal intensity. A VO2 max session that would have been at 110 percent threshold becomes 105 percent. The seven-by-three-minute lactate work becomes six-by-three. You are still trying to not blow it up.

The pattern matters more than the peaks. A consistent week of correct-zone training without one heroic session is far more useful than three good sessions and a wreck. After illness, the under-trained part of you is high-end durability, not maximum power output. Durability comes back through repetition, not maximum efforts.

Self-check at end of week 3: can you do a long brick (90 minutes ride + 30 minutes run) at endurance pace and finish able to talk in full sentences? If yes, you are ready for week 4. If no, week 3 repeats.

Week 4 — anchor sessions back at quality

Week 4 is the test. The anchor sessions return at their original prescription. The long run at race-prep duration. The long ride with the prescribed intervals. The brick with its target run-off-the-bike intensity.

One condition: you start each anchor session with a slightly longer warm-up than usual. Twenty minutes instead of ten. Build into the prescribed effort across two ramps instead of one. The body that just came back from illness needs a longer on-ramp than the body it remembers.

End of week 4 readiness markers: morning HR within 2 bpm of pre-illness baseline; recovery score 7 or above on most mornings; long ride power within 3 percent of pre-illness average for the same RPE; a quality session in each discipline executed at the prescribed intensity without crashing the day after.

If all four are true, you are back. The plan resumes at full prescription and you treat the four-week interruption as banked recovery for the next build block.

What changes inside an adaptive plan

This is what we build TriPaced around. When you log a sick week, the plan does not pretend nothing happened. It does not also dump the cycle. It applies a real four-week protocol, sized to how many days you actually missed and how your morning warnings score in week 1. Your race date stays where it is. The volume curve gets re-shaped to land you fit on race day, even if the build cost an extra week.

Your streak counts every day you spun easy or moved at all. Your weekly TSS targets shift down for weeks 1 and 2, back to baseline for week 3, and full for week 4. The Banister fitness curve absorbs the gap and tells the engine when you are actually recovered, not when you feel recovered.

You did not skip the build. You did not push through a wrecked one. You did the four-week protocol the body needed, which is what a real coach would do for you on the morning of day one back.

Show up. Adjust. Never skip a streak.

A sick week is not a write-off. A sick week is data. The body told you something. The honest response is to listen, build back over four weeks with the right protocol, and arrive at the race with the same fitness and a slightly wiser nervous system.

This is what adaptive means. Not softer. Not easier. Same destination, real protocol, less injury risk, no comeback bonk.

The four-week comeback is the difference between an athlete who treats illness as a setback and an athlete who treats it as a planned interruption with a known response. We pick the second one every time.