Height, surface firmness, and visual reference effects on balance control.

OBJECTIVES To investigate the effects of height, surface firmness, and visual reference on standing balance in construction workers. DESIGN Controlled laboratory study with balanced repeated measures. PARTICIPANTS Twenty four construction workers. SETTING Test subjects performed standing tasks at ground level as well as at 3 m and 9 m high balconies on firm or deformable surfaces with close visual references included or excluded from their visual field. METHODS Standing balance was determined from center of pressure as measured by a force platform. Dependent variables were root mean square of sway in medial-lateral and anterior-posterior directions, area of sway, and velocity of sway. RESULTS Heights without close visual references significantly increased all sway parameters. The effect of height in conditions without close visual references increased dramatically on deformable surfaces. CONCLUSIONS Elevated work environments and deformable work surfaces negatively affect balance and may be associated with increased risk of fall incidents. Appropriate close visual references increase the ability to maintain balance.