Multi-discipline load: why we don't average TSS across sports.
80 TSS on the run breaks your legs. 80 TSS on the bike doesn't. Most triathlon AI coaches sum them into one number. TriPaced keeps them apart — and balances the week using the real physiological cost of each sport.
The TSS lie
Training Stress Score was defined for cycling power data, where it does its job well. Run TSS uses pace as a proxy. Swim TSS uses pace too. Strength TSS is barely defined at all. They share a name and a scale, and that shared scale quietly invites a mistake: treating them as the same currency.
They are not. A 100-TSS run hits your joints, does eccentric muscle damage, and taxes the neuromuscular system. A 100-TSS ride is mostly aerobic with no impact and no eccentric loading. The recovery half-life differs by roughly a factor of two. Add them together and your run sessions can silently overload while your combined load still looks healthy.
Per-discipline CTL
TriPaced tracks four chronic loads — swim, bike, run and strength — each on its own exponentially-weighted window (run around 35 days, bike around 42, swim around 35, strength around 28). The athlete-state panel shows all four, ranked by your race-week priority.
Keeping them separate is what lets the engine say something useful: "you are under-doing the bike for an Ironman" — the classic age-group mistake — or "your run CTL is climbing too fast, drop a session". A single blended CTL can never tell you that, because the imbalance is precisely the thing the average erases.
Weekly distribution math
Each week is solved against several constraints at once: total available hours, bike load relative to your FTP, run load relative to your threshold pace, swim load relative to your CSS, the number of strength sessions, and the race-specificity ramp as the event approaches.
The long-ride / long-run spacing guard-rail — at least 36 hours between your two biggest sessions — lives here, applied to your actual week rather than as an abstract rule. And brick sessions (bike straight into run) carry a multiplier on the run portion, because legs that are already pre-fatigued from the ride pay a higher price for the same run minutes.
How this shows up in your dashboard
Each session is tagged with its discipline and surfaced with its own icon, so a glance tells you what today actually loads. Stretching and mobility are tracked as their own discipline rather than buried in "other". And if mid-block you decide the bike has become your bottleneck for the race, you can change the priority discipline and watch the weekly distribution rebalance around the new choice — without throwing away the load history you have already built.
Frequently asked
Why does run TSS recover slower than bike TSS?
Eccentric muscle damage from running has a longer half-life than aerobic cycling load. The acute-load window is about 7 days for both, but the soreness window for hard running is 4 to 7 days — TriPaced accounts for both through the run guard-rail set.
My bike CTL is high but my run CTL is low. Is that bad?
For a 70.3, bike-heavy can be fine. For an Ironman, both matter roughly equally past a chronic load of about 60, because the marathon is where a thin run base shows.
Should I worry about swim TSS?
Less so — swim aerobic load is a small fraction of the total. Swimming matters for race-day pacing and form; tracking volume and CSS progression beats obsessing over swim TSS.
Where does strength fit?
As its own discipline: roughly two sessions a week in build, tapering to zero in race week.
Why don't you just sum everything?
Because that is how athletes break themselves. A blended number hides the over-biked, under-run profile until it becomes an injury.
Keep reading
→ Physio guard-rails: the limits TriPaced refuses to cross
→ Ask Claude "is my run CTL too low for my Ironman?" — the TriPaced MCP server
TriPaced balances swim, bike, run and strength as four separate loads — so your build doesn't quietly over-bike and under-run you into the marathon. The beta is open and reviewed by hand.
Apply for TriPaced beta →Not ready to apply? The beta is free and open — see your real CTL, ATL and TSB, with the reasoning shown behind every change.
See the glass box for yourself →Sources. Coggan, A. & Allen, H. (2019). Training and Racing with a Power Meter, 3rd ed., VeloPress. · Daniels, J. (2014). Daniels' Running Formula, 3rd ed., Human Kinetics. · Olbrecht, J. (2000). The Science of Winning: planning, periodizing and optimizing swim training. · Schoenfeld, B. (2016). Science and Development of Muscle Hypertrophy, Human Kinetics. · Friel, J. (2024). The Triathlete's Training Bible, 5th ed., VeloPress.