Trajectory planning for a leg swing during human walking

Although locomotor patterns of many legged animals have been widely studied from a viewpoint of energetic optimality, the optimality of the leg swing trajectory has not been well studied. In this paper, we examine whether the leg swing trajectory in human walking is determined based on the criterion of the minimization of the energetic cost or not. The computed optimal leg swing trajectory shows following characteristics. (1) The foot draws an arc in the first half duration of swing phase and in the second half duration it falls down with a forward swing along a slightly curved line and then is drew back for landing. (2) The maximum height of the foot increases with walking speed. (3) The speed of the foot takes its peak value in the second half duration of swing. These characteristics were well coincident with those of experimental data of human locomotion, which indicates that the leg swing trajectory would be planned so as to minimize the energetic cost