Athlete summary
After a long hard ride, your power–duration curve shifts down: the highest sustainable power (Critical Power) and the anaerobic reserve (W′) both fall. Coaches call this durability or physiological resilience — a fourth dimension beyond VO2max, efficiency, and fresh CP (Jones, J Physiol 2023).
Koyaro therefore tracks fatigued CP and fatigued W′ as first-class numbers (watts and joules), not only “% of fresh 5-min power after 1500 kJ.”
When fatigued CP is known and enough prior work has accumulated, late-ride W′bal, race demands, and debrief use that fatigued CP as the heavy↔severe boundary — fresh CP would be optimistic.
If no fatigued test exists, Koyaro keeps fresh CP and surfaces “fatigued CP unknown.” It does not silently apply a population decay (e.g. “always −9%”).
Train vs measure: this article is the measure path. Prescribing sessions that accumulate prior work then finish with late quality is Resilience / durability training — race-pace under fatigue.
Carbohydrate during the ride matters for fatigued CP, not for W′. Norte 2026 shows graded CHO (60–120 g/h) attenuates the CP drop after prolonged work; W′ still falls. Race fueling can therefore explain 100–120 g/h as CP-preservation under fatigue when a fatigued-CP goal is set — still gated by Wilson 2025 for one-day defaults.
How Koyaro obtains fatigued CP / W′
| Method | When | Notes |
|---|---|---|
| 3-min all-out (preferred) | Fresh bout + fatigued bout after controlled prior work | End-test power (last 30 s mean) ≈ CP; W′ = work above that CP over 180 s (Vanhatalo/Jones). Control intensity, nutrition, and environment (Hunter Exp Physiol 2025). |
| Opportunistic MMP split | Ride with maximal efforts before and after a kJ split | Fit 2-param CP on MMP windows; apply only when both fits are accepted. |
| Unknown | No protocol / rejected fits | Keep fresh CP; label unknown. |
Literature anchors (golden tests)
| Source | Constraint |
|---|---|
| Clark et al., J Appl Physiol 2019 | CP ≈ −9% after ~2 h heavy work; W′ falls earlier |
| Norte et al., Scand J Med Sci Sports 2026 | Fresh CP 277 W → water 236 / 60 g·h⁻¹ 257 / 120 g·h⁻¹ 266 after 3 h @ 95% GET |
| Dudley-Rode et al., Eur J Appl Physiol 2025 | VT1 power ≈ −6% without CHO vs −3% with CHO after 150 min moderate |
CHO × fatigued CP
norte_2026_cp_retention_fraction(cho) piecewise-linear interpolates the Norte anchors. apply_cho_fatigued_cp_modifier remaps a water/low-CHO baseline fatigued CP toward a planned CHO rate (baseline_cho_g_per_hour=0); default baseline equals the target rate so opportunistic fits from a fueled ride are not double-counted. W′ is never modified. Unknown fatigued CP stays unknown even when CHO is passed.
VT1 / moderate→heavy transition power uses the same fueling×durability family via dudley_rode_vt1_retention_fraction / cho_vt1_fatigued_power_w (binary CHO vs control). Observational Pw:Hr moderate_heavy_drift_pct remains cardiac drift. Predicted late-ride VT1 from HR/FR decoupling is a complementary field signal (Fatigued VT1 from HR (FR) decoupling (Rothschild 2025)) — not a replacement for fatigued CP or kJ/kg MMP.
Literature
- Jones, J Physiol 2023 — physiological resilience as a fourth dimension
- Clark et al., J Appl Physiol 2019 — dynamics of the power–duration relationship
- Hunter, Maunder, Jones, Gallo, Muniz-Pumares, Exp Physiol 2025 (doi 10.1113/EP092120)
- Norte et al., Scand J Med Sci Sports 2026 (doi 10.1111/sms.70326)
- Dudley-Rode, Zinn, Plews, Charoensap, Maunder, Eur J Appl Physiol 2025;125:1349–1359 (doi 10.1007/s00421-024-05687-w)
- Vanhatalo / Jones — 3-min all-out CP/W′ protocol