The Effect of External Stimulus Produced by Vibration Stimulus Instrument on Body Sway

This study aimed to examine the effect of right-left or front-back vibration stimulus during standing on body sway. Subjects were 10 healthy young male adults. They had no evidence or known history of a gait, posture or skeletal disorder. After a weak vibratory stimulus (20 Hz) for 1 min, subjects stood under the strong stimulus (70 Hz) of front-back or right-left vibratory for 1 min. The subjects were measured body sway for 1 min before and after the above vibratory stimulus. Four body-sway factors (unit time sway, front-back sway, left-right sway, and the high frequency band power) were used as evaluation parameters. A significant decrease was found only in a unit time sway factor after vibratory stimulus. A significant difference between front-back and right-left vibratory stimuli was found only in a left-right sway factor and the latter stimulus produced a large change. In conclusion, even in the vibratory stimulus with the same intensity, body sway decreases after front-back stimulus, but increases after right-left stimulus. In short, the effect of vibratory stimulus on posture control system may differ by the vibratory direction.