Abstract
In this study, we measured the power spectra of body sway and of its velocity, when subjects standing upright, inclined themselves forward, and their centers of gravity shifted forward. At the same time, we calculated the variances of body sway, and examined the relation to the power spectra.
When subjects inclined themselves most forward from natural standing, the forward-backward components of the power spectra of body sway and of its velocity increased 1.98 times and 1.63 times, respectively. This occurred in the frequency ranged from 1.75 Hz to 2.50 Hz, which showed the greatest increase. The frequency ranged from 1.75 Hz to 2.50 Hz is corresponding to that of foot step. At the start of walking, the body inclines forward and its center of gravity shifts forward. With forward body inclination, the forward-backward components of the power spectra of body sway and of its velocity showed great increase. This occurred in the frequency range corresponding to that of foot step.
