Effects of pedaling speed on the power-duration relationship for high-intensity exercise

Seven males (age = 20.4 +/- 0.3 yr) each performed a total of eight exhaustive exercise bouts (four at 60 rpm and four at 100 rpm) in order to determine the influence of pedaling frequency on the parameters of the power-duration relationship for high-intensity cycle ergometry. The power-endurance time data for each subject at each rpm were fit by nonlinear regression to extract parameters of the hyperbolic: (P - theta PA). t = W', where P = power output, t = time to exhaustion, and theta PA and W' are constants. theta PA (the power asymptote, in watts (W] reflects an inherent characteristic of aerobic energy production during exercise, above which only a finite amount of work (W', in joules) can be performed, regardless of the rate at which the work is performed. theta PA at 60 rpm (235 +/- 8 W) was significantly (15.9 +/- 4.5%, P less than 0.05) greater than theta PA at 100 rpm (204 +/- 11 W), thus confirming our hypothesis that endurance would be compromised while cycling at the higher pedaling frequency. In contrast, W' was not significantly (P greater than 0.05) affected by cadence (16.8 +/- 1.7 kJ at 60 rpm vs 18.9 +/- 2.2 kJ at 100 rpm). Our data are consistent with the implications of previous investigations which demonstrated a greater cardiorespiratory and blood/muscle lactate response during constant-power exercise while cycling at high vs low rpm and indicate that the theoretical maximum sustainable power (i.e., theta PA) during cycle ergometry in untrained males is greater at 60 rpm than at 100 rpm.