Athlete summary
The TSS and Intensity Factor on a ride are still the usual power-meter numbers (one hour at FTP = 100 TSS). Heat and altitude can make the same watts cost more, because sustainable aerobic power drops.
When the file (a caller) has ambient temperature and/or altitude, Koyaro may show an extra environmental TSS / IF — clearly labeled, never written over the stored ride TSS or the fitness chart (PMC).
Heat today still scales fluid on its own path. This page is the load annotation only.
How the number is built
- Mechanical IF / TSS — unchanged Allen & Coggan (
IF = NP / FTP,TSS = hours × IF² × 100). - Capacity retention — how much of sea-level / temperate threshold the literature says remains:
- Heat < 32°C: 1.00 (no locked cycling time-trial decrement).
- Heat ≥ 32°C and < 35°C: 0.935 (Tatterson 2000: 30-min TT, 32°C vs 23°C, stated 6.5% power drop; chamber means 323 vs 345 W).
- Heat ≥ 35°C: 242.1 / 279.4 (Périard 2011: 40-km TT, 35°C vs 20°C).
- Altitude ≤ 300 m: 1.00.
- Altitude 300–2800 m: V̇O2max retention
1 − 0.063 × (altitude − 300) / 1000(Wehrlin & Hallén 2006). Above 2800 m the slope is clamped (not extrapolated).
- Combined retention is the product of the two independent cited factors. No heat×altitude synergy term is invented.
IF_env = IF / retention,TSS_env = TSS / retention².
A 6.5% capacity drop therefore raises IF by ~7% and TSS by ~14% — that quadratic step is Coggan math, not a made-up heat-TSS coefficient.
hrTSS / TRIMP are not inflated here. Heart rate already rises in the heat and at altitude; stacking a capacity multiplier would double-count.
Literature anchors (golden tests)
| Source | Locked value | Role |
|---|---|---|
| Tatterson et al., J Sci Med Sport 2000 | 6.5% (323 vs 345 W) at 32°C | Heat step |
| Périard et al., Exp Physiol 2011 | 242.1 vs 279.4 W at 35°C | Heat step |
| Wehrlin & Hallén, EJAP 2006 | −6.3% V̇O2max per 1000 m (300–2800 m); means 66 → 55 ml·kg⁻¹·min⁻¹ | Altitude capacity |
| Wehrlin TTE −14.5% / 1000 m | Cite-lock only | Not the TSS coefficient |
Heat bands are steps at the study conditions. There is no invented linear slope from 23°C to 32°C.
What this is not
- Not a rewrite of stored TSS, IF, or PMC
training_load. - Not heat fluid / sodium (
heat_fluid_multiplier/ ACSM–Sawka). - Not a heat-acclimation block.
- Not an altitude-camp Hbmass / FTP boost.
- Not an altitude-fitness score.
- Not applied to acclimated athletes as a reduced multiplier (that would invent an HA×load interaction).
Literature
- Tatterson AJ, Hahn AG, Martin DT, Febbraio MA. Effects of heat stress on physiological responses and exercise performance in elite cyclists. J Sci Med Sport. 2000;3(2):186–193. doi 10.1016/S1440-2440(00)80080-8
- Périard JD, Cramer MN, Chapman PG, Caillaud C, Thompson MW. Cardiovascular strain impairs prolonged self-paced exercise in the heat. Exp Physiol. 2011;96(2):134–144. doi 10.1113/expphysiol.2010.054213
- Wehrlin JP, Hallén J. Linear decrease in V̇O2max and performance with increasing altitude in endurance athletes. Eur J Appl Physiol. 2006;96:404–412. doi 10.1007/s00421-005-0081-9
- Allen H, Coggan AR. Training and Racing with a Power Meter — NP, IF, TSS.