Abstract: A four-seginent model of human body is proposed in this paper for thediscussion of vertical jumping motion. Assuming the rotating angle of legs as the gelleralizedcoordinate, and the variation of the position of the ground reaction force on feet as the controlfunction, the dynanucal equations are deduced to be an autonomous nonlinear equation oflst order. Analysing the phase trajectories in phase planes of angular vefocity and angularacceleration of the leg’s rotation and the curves of control functions in ...