Postural sway and EMG analysis of hip and ankle muscles during balance tasks.

Aims: This study examined how vision, base of support (BOS) and surface compliance affected postural sway and electromyography (EMG) activity of hip and ankle muscles during eight balance training tasks in young adults, Methods: Postural sway and EMG activity of gluteus maximus (GMAX), gluteus medius (GMED), tibialis anterior (TA), and medial gastrocnemius (GAST) were measured during eight balance tasks with eyes open or closed, feet in tandem or apart, and on foam or a firm surface. Results: Postural sway and EMG activity of hip and ankle muscles were significantly affected by the alteration of vision, surface compliance or BOS during eight balance tasks (P<0.05). There was more postural sway when the number of sensory factors altered in the balance tasks increased. GMED and TA EMG activity increased significantly in tasks with tandem standing; GMAX was recruited significantly only when vision was excluded in tasks with tandem standing; and GAST EMG activity was significantly higher in tasks on the foam and in tandem standing. Conclusions: Balance exercises may be progressed according to the rank of the task's difficulty by increasing the number of sensory factors altered in a balance task. There was significant recruitment of hip and ankle muscles in the balance tasks indicating the importance of these muscles in postural control. [ABSTRACT FROM AUTHOR]