Abstract
The incessant sway of the point of application of the floor reaction even in the most comfortable standing posture is well recognized and has been studied by various methods. Research results are expressed in static terms rather than in dynamics: an average and standard deviation of the sway trajectory for a certain time period are often studied, but as to the dynamics only the frequency analysis is carried out to give some idea of its unsteadiness. In this paper we applied the autoregressive modeling technique to the experimental data obtained by force plate for various conditions; standing normally or on one leg with eyes open/closed. The characteristics estimated by the model were compared with corresponding measured values with respect to the distribution of swaying speed and power spectrum to show the validity of the model. An affirmative result was obtained for each of three standing conditions. The result, also, showed that the variance of the random noise introduced in the modeling process corresponded well to the violence of the sway. The subjects included not only cerebral palsy children but also normal adults standing normally or standing on a single leg with eyes closed to study various standing conditions.
