Control of standing posture with change in the center of foot pressure by following a moving target at low velocity / 体力科学

ABSTRACT

The purpose of this study was to evaluate the relationship between the position of the center of foot pressure (CFP) and control of standing posture in ten healthy men by tracking the CFP to the moving target.<BR>Subjects were required to track a continuously moving target displayed on a screen while standing on a force plate. The velocity of the target movement was 0.05, 0.10, and 0.15 hertz (Hz) with a triangular waveform. The target was moved 30-70% within the range of the heel regarding the foot length as 100%, and the range was divided by 10%. Each subrange was named (A), (B), (C), (D) for backward movement from 70% to 30%, and (E), (F), (G), (H) for forward movement from 30% to 70%.<BR>The standing posture control was analyzed by mean error and absolute error at turning point between target- and CFP-movement.<BR>The mean error of backward movement was significantly greater than that of forward movement in the two forward subranges at 0.15 Hz. As for the other frequencies, there was no significant difference between directions of CFP movement. Mean error of A was significantly greater than that of B and C in higher frequencies, but there was no significant difference at 0.05 Hz. Regarding absolute error, there was no significant difference between the forward and backward turning point with a decrease in frequency. Mean error of D or E was greatest among the section in all frequencies. The ratio of the greater D or E and A or H was greatest at 0.05 Hz.<BR>These results suggested that CFP tracking at 0.05 Hz is hardly influenced by direction and velocity of the target movement. Terefore, we conclude that controllability of the stand-ing posture differs markedly in various CFP positions. In addition, control of the standing posture in a backward direction is inferior to that in a forward one.