Fig. 1.

Hyperbolic power-duration curve that defines the sustainable duration of exercise in the severe-intensity domain. This hyperbolic relationship is defined by two parameters: the power asymptote, known as the critical power (CP), and the curvature constant W′ (denoted by the rectangular dashed blue lines above CP and expressed in kilojoules). Critical power defines the boundary between the heavy- and severe-intensity exercise domains and represents the highest power output for which a metabolic steady state may be attained. The W' comprises a fixed and finite volume of work that is expendable above CP. During severe-intensity exercise, task failure occurs when W′ = 0. GET gas exchange threshold