Trajectory of the body COG and COP during initiation and termination of gait

Five initiation and five termination plus three steady-state walking trials were collected for each of four subjects using three videos cameras and three force platforms. Data were analysed using a 13-segment three-dimensional biomechanical model. During initiation 90% of steady-state velo-city was achieved during the first step and 100% by the second step. During termination, 10% of the velocity was reduced in the first step and 90% in the last step. The interaction between the centre of mass (COM) and centre of pressure (COP) is tightly regulated to control the trajectory of the COM and thereby control total body balance. Coarse control of this balance is achieved by foot placement, with fine control during weight bearing by the ankle musculature.