Simple models of walking and jumping

Abstract Many biomechanical models of human movement are complex by the standards of physical mechanics, but this paper presents two that are exceedingly simple. The first helps to explain the transition from walking to running by showing that a straightlegged style of walking would become impossible above a certain speed. The second uses the force-velocity properties of muscle to explain why high jumpers run up much more slowly than long jumpers. Simple models are particularly useful in identifying basic principles because the simpler the model, the easier it is to discover which of its features gives rise to the observed effect.