Athlete summary
Efficiency Factor (EF) is how much power you produce per heartbeat (Normalized Power ÷ heart rate). Over weeks, a rising EF on similar endurance rides usually means aerobic fitness is improving.
Aerobic decoupling (Pw:Hr drift) compares EF in the first half of a ride to the second half. A large drop means heart rate climbed relative to power — often heat, fueling, or aerobic strain.
Formulas (engine)
- EF:
rolling_30s_NP / HR(summary and/streams). - Decoupling:
(EF_first − EF_second) / EF_first × 100. - The catalog cue: decoupling > 5% suggests aerobic strain on a steady endurance ride. The engine does not invent a different cutoff.
Both need a usable power stream and heart rate. Missing HR → no EF, no decoupling.
What this is not
- Not a readiness score (see Multi-signal morning gate for quality days (HRV + RHR + wellbeing)).
- Not fatigued CP / durability (see Fatigued Critical Power and W′ after prior work).
- Not HR-only load (hrTSS / TRIMP) — see HR-only load, Karvonen zones, and Banister TRIMP.
Citations
- Friel / TrainingPeaks Pw:Hr and Efficiency Factor practice (endurance-ride coupling). Thresholds above are the catalog’s documented cue, not a new model.