The effect of bicycle crank-length variation upon power performance.

Abstract

The purpose of the present study was to define the optimal bicycle crank length (CL) for eliciting maximal leg power output during a 30 s power test (Wingate Anaerobic Test). Thirteen male students 22-27 years old served as subjects for this study. In each of the five sessions the test was administered on a mechanically braked cycle-ergometer modified by a crank slider-assembly which permitted continuous crank-length adjustment. Five evenly spaced CLs, centred around the conventional 17.5 cm crank, ranging from 12.5 to 22.5 cm, were used. The measured variables were mean (MP) and peak (PP) power output. A parabola-fitting technique was employed to define the optimal CL from the MP and PP data. The resulting optimal CL was 16.4 and 16.6 cm for MP and PP, respectively. Optimal CL was shown to depend on leg length. However, within a two crank length span (± 5 cm) about the optimal crank length MP and PP did not vary by more than 0.77 and 1.24% respectively. It is suggested that for a homogenous population, such as used in this study, the conventional 17.5 cm crank is close to the calculated optimum for power production. However, a failure to adjust this factor to the anthropometric dimensions of populations, heterogenous in size, may result in a much greater fall-off in cycle short-term power performance.