Normal human locomotion.

A study of normal locomotion requires an understanding of both the movements and the force actions involved. This is equally true in appreciating the problems of pathological gait. The gait cycle is described in terms of the significant events which occur during both the stance and swing phases. The basic principles underlying the analysis of force actions in walking are briefly described. A simple example of force actions in the elbow joint is considered and the analysis extrapolated to provide a general statement regarding locomotion. This relates to the muscle actions required to resist turning actions at joints due to the force effects in walking and the corresponding forces in the joints themselves. The conventional display of information relating to joing actions is considered and compared with the actual situation, "Stick diagrams" of motion in the sagittal plane are used to identify and discuss the actions at the joints of the leg in walking. Comparisons are made between this and pathological gait--in particular that of the above-knee amputee.