Physiological efficiency of constant power output at varying pedal rates

Abstract

The study investigated the absolute and relative (% maximal) physiological demands of constant power output at three pedal rates chosen to incorporate the range used by racing cyclists. Following the assessment of maximal exercise capabilities utilizing a recently developed racing cycle ergometry system, ten highly trained racing cyclists undertook a randomized sequence of work bouts at low (70.0 ± 1.1), medium (94.8 ± 0.8) and high (126.5 ± 1.1) pedal rates per minute at constant power output under an unloaded (free wheel) condition and under a loaded (196.2 ± 8.0 W) condition which demanded approximately 75% VO₂ max. In both the unloaded and loaded conditions absolute cardiorespiratory demands of work at the highest pedal rate were significantly higher than those at the low and medium pedal rates (P<0.05). Similarly, the relative (% max) cardiorespiratory demands of unloaded work at the highest pedalling rate were significantly greater that at low and medium pedal rates (P < 0.05). There were clear, but nonsignificant trends of elevated relative cardiorespiratory demands during loaded work at the highest pedal rate, compared with low and medium pedal rates. Furthermore, net muscular efficiency demonstrated a significant decline (P<0.01) at the highest pedalling rate (21.2%) compared with the medium (24.0%) and low (25.6%) pedalling rates, confirming that metabolic economy of constant power output declined with increased pedalling rate under simulated racing cycling conditions.

Key Words:

• Cycling efficiency
• pedal rate
• racing cyclists