Energy estimates from force plate data

Abstract

In this paper, we discuss a possibility of evaluating a part of the energy cost for maintaining a vertical posture by a person. We use the stabilometric data (center of pressure (CoP) postural sway measurements) only. The application of an inverted pendulum model for calculating the components of the mechanical work of particular groups of leg muscles is described. We use integral of the modulus of the power of total torques developed by the antagonists. For the sagittal direction, the mechanical work of muscles of the ankle is make an estimate mainly, and for the frontal direction – of the pelvic muscles. The possibility of using approximate estimates of energy indicators for the slow components of human movement is discussed. To analyze the correlations of various indicators, the results of postural stability tests were used. During these tests the subjects stood with their eyes open in an upright posture. Moreover, in several tests, they were presented with various visual illusions. It was causing a change in postural characteristics and, accordingly, stabilometric parameters. The correlations between the introduced energetical indicators and indicators traditionally used in stabilometry are analyzed. The next indicators: CoP trajectory range of oscillations along the frontal and sagittal, the average CoP velocity and its projection on the frontal and sagittal axes, as well as an indicator called the "total energy density of statokinesiogram" and its components for the frontal and sagittal directions were considered. A correlation between the used indicator of mechanical work and the stabilogram range was developed. It is shown that the change in a part of the energy corresponding to an indicator called the “total energy density of statokinesiogram” is small and, apparently, does not adequately characterize the change in mechanical energy.