Effects of differing pedalling speeds on the power-duration relationship of high intensity cycle ergometry

Abstract

The aim of this experiment was to investigate the effects of differing pedalling speeds on the power-duration relationship during high intensity cycle ergometry with pedal cadences of 50 (low), 90 (intermediate) and 110 (high) r.min-1. This hyperbolic power-duration relationship can be described as: (P - phiPA).t = W', where P = power output, t = time to exhaustion, and phiPA and W' are constants. Eight volunteer male subjects, aged 24 +/- 2.6 yr, with no competitive cycling training took part in this study and each undertook thirteen tests on a Lode BV Excalibur Sport V1.52 cycle ergometer over an eight week period. The first exercise bout was a 30 W.min-1 incremental cycle at 50 r.min-1 to volitional fatigue. This allowed the identification of a range of power outputs that would be used to construct and examine the power-duration relationships for each subject at 50, 90 and 110 r.min-1. At both 50 and 90 r.min-1, power outputs of 30 W above and below and 60 W above the highest work rate, as well as the maximum work rate achieved during the incremental exercise test were chosen, while at 110 r.min-1, the power outputs chosen were 25 W above and below as well as 50 W above the highest work rate achieved during the incremental exercise test and also the maximum work rate achieved during the incremental exercise test were chosen. These four work rates for each pedalling frequency were chosen because they would have exercise times to exhaustion in the range of 1-10 minutes. Each exercise bout was preceded by four minutes of unloaded cycling and then the work rate was adjusted quickly to the desired load setting by the previously programmed computerised ergometer. The results of this work indicate that for the group of subjects studied, pedalling a cycle ergometer at 50 r.min-1 allows subjects to pedal for a significantly greater time than when pedalling at either 90 or 110 r.min-1. phiPA at 50 r.min-1 was significantly greater than when pedalling at either 90 (F(1,21) = 7.47, p < 0.01) or 110 r.min-1 (F(1,21) = 10.83, p < 0.0005). There was no significant (p > 0.22) difference between phiPA at 90 and 110 r.min-1, F(1,21) = 1.36. W' however, was not significantly different when the data for 50 r.min-1, 90 r.min-1 and 110 r.min-1 were compared (F50 r.min-1 (1,21) = 0.95; p > 0.41; F90 r.min-1(1,21) = 0.79, p > 0.53; F110 r.min-1 (1,21) = 0.78, p > 0.53). Our hypothesis, that endurance performance was reduced when recreational cyclists pedal at a high cadence when compared to a low cadence was correct. Maximum sustainable power output during cycle ergometry was higher at 50 r.min-1 than at either 90 or 110 r.min-1. At the intermediate cadence endurance was better than at the high but worse than at the low cadence. In conclusion, during endurance cycling, recreaional cyclists should pedal at lower rather than higher cadences.