The purpose of this study was to evaluate the changes in the electromyographic (EMG) activity of the trunk and the lower limb muscles during quiet standing on an unstable surface while wearing low-heeled shoes (3 ㎝), high-heeled shoes (7 ㎝) and without footwear (0 ㎝) in 20 young healthy women. The subjects stood on an unstable surface for 30 seconds. We examined the differences in the EMG data of the erector spinae, rectus abdominis, biceps femoris, rectus femoris, tibialis anterior, and the gastrocnemius medialis muscle. A one-way repeated analysis of variance was used to compare the effects of shoe heel height on the EMG activity with the level of significance set at α=.05. The EMG activity of the erector spinae and the rectus femoris were significantly increased (p<.05) in the subjects who wore elevated heel height, while the tibialis anterior and the gastrocnemius medialis were significantly decreased (p<.05). However, the rectus abdominis and the biceps femoris exhibited no significant difference among the three conditions. The above results indicate that wearing high-heeled shoes may change the postural strategy. The findings of this study suggest that excessive heel height could contribute to an increased fall risk during quiet standing.

The purpose of this study was to compare the muscle activity during a push-up on a suspension sling and a fixed support at the same level. Tests were performed on 15 male subjects. Electromyography using a surface EMG recorded the activity of the triceps, pectoralis major, and internal and external oblique muscles during each push-up. EMG activity was recorded at 0, 45, and 90 degrees of elbow flexion in the push-up position on a suspension sling or a fixed support at the same height above the floor (30 cm). The testing order was selected randomly. The subjects were asked to maintain the push-up position with straight knees, hips, and trunk for 5 seconds at each elbow angle. The mean root mean square (RMS) of EMG activity was calculated. EMG activity was normalized using the maximum voluntary isometric contractιn elicited using a manual muscle testing technique. Two-factor repeated measures analysis of variance (ANOVA) was used to compare the average RMS value of EMG activity for each condition. The EMG activity for the pectoralis major, and internal and external oblique muscles during a push-up on a sling was significantly higher than on a fixed support at all angles of elbow flexion (p<.01). There were significant differences in the EMG activity of the pectoralis major and triceps brachii muscles at difference angles of elbow flexion (p<.05). The pectoralis major muscle had the highest EMG activity at 90 degrees of elbow flexion on both the sling and fixed support. The triceps brachii muscle had the highest EMG activity at 45 degrees of elbow flexion on both the sling and fixed support. The internal and external oblique muscles had the highest EMG activity at 0 degrees of elbow flexion, although the difference with angle of flexion was not significant. These results suggest that to improve proximal and trunk stability and muscle strength, push-ups are more useful when performed on a suspension sling than On a fixed support.