Effect of pedal rate, brake load and power on metabolic responses to bicycle ergometer work

In earlier investigations of the energy cost of bicycle ergometer work, pedal rate and brake load have been varied simultaneously while maintaining a constant power, thus confounding the effects of these factors. A two-way factorial design was used to isolate the effects of rate and load upon metabolic responses during ergometer work while also determining any interaction of effects (a power effect). Nine men performed bicycle ergometer tests at five pedal rates (20-100 r.p.m.) with five brake loads at each rate (0-4 kp). Steady-state V˙O2 was found to be a quadratic function of pedal rate when brake load was held constant, and to be a quadratic function of brake load when pedal rate was held constant. There was a significant interaction between the effects of rate and load which resulted in a shifting of the most efficient rate-load combination as the power changed. Significant differences (10-29%) were found between rate-load combinations at a constant power. It was concluded that the energy cost of bicycle ergometer work is not linearly related to the work output, but rather depends on the rate and force with which the work is accomplished.