The Effect of Balance Task Difficulty and Visual Feedback on EMG Activity of Selected Muscles in Elderly Women

The purpose of present study was to determine the effect of different levels of balance task difficulty and visual feedback on EMG activity of selected muscles in elderly women.

Fourteen healthy elderly women )mean age 57/65 yr( were voluntarily selected. The task consisted of performing balance task on Biodex Balance System. Participants were asked to stand still on a stability platform under two conditions (with and without visual feedback) in three levels of difficulty (6, 8 &10). Megawin EMG system was used for recording electromyography of rectus femoris, gastrocnemius, preroneus longus and biceps femoris muscles and RMS of EMG signals was obtained. Duration of each test was 20 seconds and rest times were 20 seconds.

Results showed that with increasing task difficulty, preroneus longus (p= 0/01), biceps femoris (p= 0/028), rectus femoris (p< 0/001) and gastrocnemius (p= 0/01) EMG activity increased significantly. In addition, there was a significant increase in preroneus longus (p= 0/01), biceps femoris (p< 0/001) and rectus femoris (p< 0/001) EMG activity in visual feedback condition compared with without feedback condition.

As task difficulty increased and with visual feedback, the elderly did not choose between two postural strategies but tend to combine movements in continuous behavior and they use the body stiffness strategy to improve balance.