Mechanical energy generation, absorption and transfer amongst segments during walking.

The purpose of this paper was twofold: firstly to measure and partially validate the rates of work done (powers) by the joint reaction forces and moments on the leg segments and secondly to explain the changes in mechanical energy of the segments by the transfer, generation or absorption of energy by the muscles and/or the transfer of energy through the joints. Measurement of the powers required the calculation of segmental kinematic information and joint reaction forces and moments. Force plate and cinefilm data were collected on two subjects walking at several walking speeds using a sagittal plane, linked, rigid body model of the human form. The total powers delivered to or taken from the segments (t%‘t) were compared with the corresponding segmental rates of change ofmechanical energy (I?). The work-energy theorem holds that these two measures are equal, however, modelling assumptions and approximations made to simplify the structure of the human body may cause considerable discrepancy. Thus, a comparison of these two measures can assess whether the human model is valid and hence whether the two measures are accurate. Results indicate that the model and therefore the power measures were valid excepting the ankle powers during weight acceptance and late push-off. The rates of transfer of energy through the joints and muscles were found to be comparable in magnitude to the rates of energy generation and absorption by the muscles. Thus, the joint energy transfers perform a significant role in the mechanical energy variations of the segments during walking.