Change of Postural Control in Cooling of the Each Planter Surface of the Feet / 体力科学

ABSTRACT

This study focused on the effect of pressure sensation from the each plantar surface of the feet on postural control. The plantar surfaces of the feet were made less sensitive by cooling, using a specially designed apparatus set on a force plate. Three areas were cooled the plantar surface of the heel, the forefoot, and the entire plantar surface of the foot. And the non-cooling condition was the control. The subjects, seven healthy men, were asked to track a continuously moving target spot displayed on a visual monitor while standing on the force plate. This tracking was done by controlling the center of foot pressure (CFP) by leaning forward and backward at the ankles. The target was moving at 0.025 Hertz (once per 40 seconds) with a triangular waveform. The moving range of the target was from 30 to 70 percent (%) of the total foot length from the heel, and this range was divided into 10 percent (%) subranges. Postural controllability was evaluated by the difference between movements of the CFP and target for each subrange. When the entire surface of the foot was cooled, postural controllability of moving the CFP anteriorly was significantly worse than the control. Postural controllability of moving the CFP anteriorly for the anterior and the posterior moving subranges was significantly worse than the control when the heel was cooled. When the forefoot was cooled, postural controllability of moving the CFP anteriorly for the anteriorly moving subrange was significantly worse than that of the control. These results suggest that pressure sensation from the plantar surface definitely participates in moving the CFP anteriorly for postural control. When the CFP is situated on the heel, pressure sensation from the heel alone may play a necessary role for postural control. When the CFP is situated on the forefoot, however pressure sensation from the forefoot may need to be the supplemented by sensation from the heel for adequate postural control.