Influence of fingertip contact with a wall on postural sway and electromyographyic activity of the soleus muscle.

Standing and walking balance decreases in many kinds of neuromuscular, musculoskeletal and sensory disorders, and in elderly people because of age-related physiologic diminution. Recent studies have shown that contact cues from a cane or a fingertip provide information that leads to reduced postural sway in subjects. The first purpose of this study was to investigate the influence of light and forceful fingertip contacts with a wall on the postural sway while standing upright. The second purpose was to investigate the influence of fingertip contact on the EMG activity of the soleus muscle. Twelve healthy male volunteers (20.8 +/- 0.7 years old) participated in this study. Standing balance or postural sway was measured by sway of the center of pressure (COP) under three conditions: (1) standing without touching a wall, (2) standing with the right index fingertip lightly touching (< 1N) to a wall (3), and standing with the right index fingertip forcefully touching (5 approximately 10N) to a wall. Bipolar surface electrodes were placed over the right soleus muscle to measure EMG activity associated with anterior-posterior sway. More significant length, and rectangular and environmental areas of the COP were observed while standing without touching a wall than while standing while lightly or forcefully touching a wall, but there was no significant difference between the two touching conditions. No significant difference in the EMG activity of the soleus muscle was observed among the three conditions. The results of this study suggested that the fingertip touch contact with a wall decreased sway during static standing but did not influence the EMG activity of the soleus muscle.