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 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-P(A)). t = W', where P = power output, t = time to exhaustion, and theta-P(A) and W' are constants. theta-P(A) (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-P(A) at 60 rpm (235 +/- 8 W) was significantly (15.9 +/- 4.5%, P < 0.05) greater than theta-P(A) 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 > 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-P(A)) during cycle ergometry in untrained males is greater at 60 rpm than at 100 rpm.