Athlete summary
Measuring how much power you keep after prior work is not the same as training that quality. Profiling lives in Fatigued Critical Power and W′ after prior work and durability v2. This article is the session you ride when late-race power is the limiter.
Koyaro’s opt-in durability / resilience day:
- Accumulates controlled work below LT2 / at race-easy (time under fatigue).
- Finishes with late quality — e.g. Spragg’s practical 5×8 min @ ~105% CP, or a progressive late intensity rise.
- Pairs with planned CHO / fatigued-CP fueling intent.
Language stays best available / emerging. There are no dedicated RCTs proving a % durability gain from this structure — Jones & Kirby (2025) say so explicitly.
Measure vs train
| Profiling (measure) | This article (train) | |
|---|---|---|
| Question | How much CP / MMP do I keep after work? | When do I prescribe the session that trains that? |
| Engine | metrics/durability.py, fatigued CP | planning/durability_sessions.py |
| Output | cp_fatigued_w, retention %, progression charts | Pre-fatigue + late quality workout |
| kJ/kg dual-axis | Measure path shipped (metrics/durability.py); this role still uses time-below-LT2 |
What the engine locks
| Constraint | Engine behavior | Citation |
|---|---|---|
| Role | Calendar role durability (high band) | |
| Prior work | Steady ~68% FTP (below LT2 / race-easy) | Jones & Kirby 2025 |
| Late quality A | 5×8 min @ ~105% CP — catalog illustration, not a locked law | Spragg 2023 |
| Late quality B | Progressive tempo → threshold → short VO2 (equal alternative) | Jones & Kirby |
| Fresh VO2 | Unchanged default 4×4-style template | Anti-regression |
| Fueling | fatigued_cp_goal=True for this role | |
| Spacing / TSB | Quality-day spacing + hard-role guards | |
| Claims | “Best available / emerging” only | Science CLEAR |
What this is not
- Not a proprietary durability-score progression target.
- Not a replacement for long-ride volume policy.
- Not off-bike heavy strength — that concurrent lever is Strength for cyclists — heavy ≥80% 1RM; efficiency and anaerobic power.
- Not CHO×fatigued-CP dose-response math (owns that).
- Not the kJ/kg measure path — that lives on the durability profile.
- Not a claim of RCT-proven % durability gains.
Literature
- Jones AM, Kirby BS. Physiological resilience: what is it and how might it be trained? Scand J Med Sci Sports. 2025;35:e70032. doi:10.1111/sms.70032
- Jones AM. The fourth dimension: physiological resilience as an independent determinant of endurance performance. J Physiol. 2024. doi:10.1113/JP284205
- Spragg J, Leo P, Swart J. The relationship between physiological characteristics and durability in male professional cyclists — fatiguing protocol 5×8 min @ 105–110% CP (catalog late-quality recipe uses ~105% CP). Med Sci Sports Exerc. 2023;55:133–140. doi:10.1249/mss.0000000000003024
- Sánchez-Jiménez et al. Is intensity the most important factor… cyclists’ acute durability? Eur J Appl Physiol. 2026;126:163–179. doi:10.1007/s00421-025-05885-0