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 approximately 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) > or = 0.995). 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.