Cycling efficiency and pedalling frequency in road cyclists

The purpose of this study was to determine the influence of pedalling rate on cycling efficiency in road cyclists. Seven competitive road cyclists par ticipated in the study. Four separate experimental sessions were used to de termine oxygen uptake ((V) over dot O-2) and carbon dioxide output ((V) ove r dot CO2) at six exercise intensities that elicited a (V) over dot O-2 equ ivalent to 54, 63, 73, 80, 87 and 93% of maximum (V) over dot O-2 ((V) over dot O-2max). Exercise intensities were administered in random order, separ ated by rest periods of 3-5 min; four pedalling frequencies (60, 80, 100 an d 120 rpm) were randomly tested per intensity. The oxygen cost of cycling w as always lower when the exercise was performed at 60 rpm. At each exercise intensity, (V) over dot O-2 showed a parabolic dependence on pedalling rat e (r =0.99-1, all P < 0.01) with a curvature that flattened as intensity in creased. Likewise, the relationship between power output and gross efficien cy (GE) was also best fitted to a parabola (r = 0.94-1, all P < 0.05). Rega rdless of pedalling rate, CE improved with increasing exercise intensity (P < 0.001). Conversely, GE worsened with pedalling rate (P < 0.001). Interes tingly, the effect of pedalling cadence on GE decreased as a linear functio n of power output (r = 0.98, n = 6, P < 0.001). Similar delta efficiency (D E) values were obtained regardless of pedalling rate [21.5 (0.8), 22.3 (1.2 ), 22.6 (0.6) and 23.9 (1.0)%, for the 60, 80, 100 and 120 rpm, mean (SEM) respectively]. However, in contrast to GE, DE increased as a linear functio n of pedalling rate (r = 0.98, P < 0.05). The rate at which pulmonary venti lation increased was accentuated for the highest pedalling rate (P < 0.05), even after accounting for differences in exercise intensity and (V) over d ot O-2 (P < 0.05). Pedalling rate per se did not have any influence on hear t rate which, in turn, increased linearly with (V) over dot O-2. These resu lts may help us to understand why competitive cyclists often pedal at caden ces of 90-105 rpm to sustain a high power output during prolonged exercise.