The effects of crank power and cadence on muscle fascicle shortening velocities, muscle activations and joint-powers during cycling.

Abstract

Whilst people typically chose to locomote in most economical fashion, during cycling on a bicycle they will, unusually, chose cadences that are higher than metabolically optimal. Empirical measurements of the intrinsic contractile properties of the vastus lateralis (VL) muscle during submaximal cycling suggest that the cadences that people prefer (i.e., self-selected cadences: SSC) allow for optimal muscle fascicle shortening velocity for the production of knee extensor muscle power. It remains unclear, however, whether this is consistent across different power outputs where SSC is known to might be affected. We examined the effect of cadence and external power requirements on muscle neuromechanics and joint powers during cycling. VL fascicle shortening velocities, muscle activations and joint-specific powers were measured during cycling between 60 and 120rpm (and the SSC), while participants produced 10%, 30%, and 50% of peak maximal power. VL shortening velocity increased as cadence increased but was similar across the different power outputs. Although no differences were found in the distribution of joint powers across cadence conditions, the absolute knee joint power increased with increasing crank power output. Muscle fascicle shortening velocities increase in VL at the SSC as pedal power demands increase from submaximal to maximal cycling. It therefore seems highly unlikely that preferred cadence is primarily driven by the desire to maintain "optimal" muscle fascicle shortening velocities. A secondary analysis of muscle activation patterns revealed that minimizing muscle activation is likely more important when choosing a cadence for given pedal power demand.