Work done above critical power costs disproportionately more fatigue than equivalent work below it
Interpretation
The W′ reconstitution model (Skiba 2014, extended by Caen 2019) and variable-vs-constant-power fatigue research (Theurel & Lepers 2008) converge on the same point: spending capacity above critical power is categorically more costly than equivalent work below it, and recovery of that capacity is slower and more partial than intuition suggests. The on-device W′-balance number is a useful directional model, not a precise instrument — it's built from fresh-state lab data and carries real estimation error.
Practical implication
A pacing-rule engine should weight time-above-critical-power much more heavily than average power when estimating fatigue cost, and should treat on-device W′-balance readouts as approximate, especially late in long events.
Sources
4 sources, independently verified.
Volume 46(7):1433-40. The foundational W′-balance reconstitution model underlying every on-bike-computer W′ estimate — tested how varying work/recovery durations affects how much of the anaerobic work capacity (W′) refills during intermittent exercise. Could not independently confirm an exact DOI for this specific title/author/year combination after two search passes (a related 2012 Skiba/Chidnok/Vanhatalo/Jones MSSE paper, DOI 10.1249/mss.0b013e3182517a80, covers closely related ground) — verify manually before treating the DOI as settled.
Extends the Skiba W′ reconstitution model — found reconstitution depends on characteristics of both the preceding work and the recovery interval, not recovery duration alone. Could not independently confirm a DOI or exact venue after two search passes — verify manually.
Two 33-min trials at identical average power — one constant (70% max aerobic power), one variable (alternating high/moderate). Neuromuscular fatigue was greater after the variable-power trial despite identical average power, directly supporting the 'surges cost more than steady riding at the same average' principle.
Found high-intensity efforts (above critical power) produced greater power-output reductions with less accumulated work than low-to-moderate intensity efforts — 10-20% power declines seen after just 2.5-15 kJ/kg of prior high-intensity work. Concludes kJ alone is an insufficient fatigue metric; intensity distribution matters.