The relationship between power and time to fatigue in cycle ergometer exercise

The purpose of this study was to evaluate three critical power (P-critical) models. Ten university students performed tests that elicited fatigue in > 2 min to similar to 10 min. Power and time data were fit to a 2-parameter hyperbolic model, a 3-parameter hyperbolic model, and a 3-parameter exponential model. Models described the power-time relationship well (R-2 greater than or equal to0.995). However, P-critical (209 +/- 51 W; SEE: 20 +/- 47 W) and the time constant (198 +/- 87 s; SEE: 103 +/- 246 W) from the exponential model have no obvious meaning. The 2-parameter model produced P-critical (187 +/- 38 W) and anaerobic work capacity (20.4 +/- 9.0 kJ) that have known physiological meaning, with excellent confidence (SEE: 2 +/- 2 W and 1.0 +/- 1.0 kJ, respectively). Addition of a maximal power parameter to the 2-parameter model did not improve description of the relationship, and the third parameter was superfluous. The 2-parameter model was preferred because, for the range of exercise durations used in this study, it describes the power-relationship adequately and in a most parsimonious fashion.