Critical Power / W′ (2 efforts)

Two maximal efforts of distinct durations reveal CP (sustainable threshold) and W′ (anaerobic reserve) through a mathematical model.

Protocol

Perform two maximal efforts of clearly distinct durations (e.g., 3–5 min and 12–20 min), with full recovery between them. Record the average power (P1, P2) and duration (t1, t2) of each. Durations that are too close together reduce the model’s confidence — keep a clear gap between them.

Formula

W′ = (P1 − P2) / (1/t1 − 1/t2)

CP = P1 − W′/t1

CP (Critical Power) is the reported threshold value (equivalent to FTP); W′ is the anaerobic work reserve (in Joules), shown as an extra.

Physiological basis

The Critical Power model, formalized by Monod & Scherrer (1965), is considered the most robust physiological basis among the methods offered here — widely validated and peer-reviewed for describing the hyperbolic relationship between intensity and time to exhaustion.