Effects of Changes of Foot Position on Romberg's Quotient of Postural Sway and Leg Muscles Electromyographic Activities in Standing.

Changing of standing position and visual blocking methods have been used as a convenient evaluation of standing balance by physical therapists. The purpose of this study was to investigate the effects of changes of foot positions on Romberg's quotient of postural sway and the tibialis anterior and gastrocnemius muscles activities in standing for normal men. Subjects were 45 college students. For the measurement of muscles activities, 15 subjects were selected at random from among the 45 students. The standing positions were standing with legs 10 cm apart, standing with legs together, tandem standing, standing on tiptoes, and standing on one leg with the eyes open and closed. Measurements were made using a center of foot pressure recorder and surface electromyography for 30 seconds. Romberg's quotient and the relative muscle activities of the leg were both found to be in the order standing with legs apart, standing with legs together, tandem standing, standing on tiptoes, standing on one leg. It has conventionally been considered that the instability of postural sway is increased when vision is blocked. The present results suggested that postural regulation by the physiological subsystem is indirectly affected by vision and somatosensory input.