A THEORY OF METABOLIC COSTS FOR BIPEDAL GAITS

A simple model predicts the energy cost of bipedal locomotion for give n speed, stride length, duty factor and shape factor. (The duty factor is the fraction of stride duration, for which a foot is on the ground , and the shape factor describes the pattern of force exerted on the g round). The parameters are varied to find the gait that minimizes meta bolic energy cost, for each speed. A previous model by Alexander calcu lated the work that the muscles have to do, but the metabolic cost (ca lculated in this paper) is more likely to be the principal criterion f or gait selection. The model gives good predictions of human stride le ngths, and of the speed at which we break into a run. It predicts lowe r duty factors and higher shape factors than are normally used, but th e relationships between these gait parameters and speed parallel the e mpirical relationships. (C) 1997 Academic Press Limited.