FORCES AND ENERGY CHANGES IN THE LEG DURING WALKING

The study of locomotion yields information not only concerning the mechanics of progression but also concerning the part that muscles play in this intricate activity. Early attempts at a quantitative analysis of human locomotion were made by the Webers, Marey and Otto Fischer, followed in recent years by Bernstein (1927, 1935) and by Fenn (1929, 1930). The present paper is concerned with a detailed analysis of the dynamics of the human leg in walking, providing data concerning muscle function. In his fundamental investigations of the kinematics of walking, Fischer (1901) was hindered by the fact that he could not determine the point of application of the force exerted by the ground on the foot. The path of this point during the time the foot is on the ground was determined by Elftman and Manter (1934) from cinematic records of pressure distribution in the foot, obtained by a method described by Elftman (1934). For the purposes of the present research, however, a new apparatus has been devised (Elftman, 1938), which gives not only the point of application of this force, but also the magnitude of the force in three components. In addition to solving Fischer's difficulty, this obviates the necessity of dealing with the entire body when only one portion, such as the leg, is of immediate interest. The point of application of this force, as it passes forward during the course of the step, is shown in figure 1. The force itself is plotted in two components, one in the plane of progression, the other lateral, in the horizontal plane. Only the component in the plane of progression will be considered in the present discussion. It is apparent from the diagram that it has two maxima and that it is at first directed upward and backward against the foot, later upward and forward. This reaction of the platform is plotted in figure 6 in two components, one vertical and the other horizontal, in the plane of progression. In addition to this knowledge concerning the external force exerted by the platform, it is necessary to know the disposition of the leg in space. This is shown in figure 2 for the left leg during the double step under con-339 340 HERBERT ELFTMAN sideration. The original information was obtained from cinematic records taken at the rate of 92 exposures per second as the subject walked behind a rectangular grid. The timing was …