Effects of real-time visual biofeedback of pelvic movement on electromyographic activity of hip muscles and lateral pelvic tilt during unilateral weight-bearing and side-lying hip abduction exercises.

Although neutral pelvic alignment is important for hip abduction exercises, studies exploring objectively monitored pelvic alignment on the gluteus medius (Gmed) muscle activity during hip abduction exercises, especially under weight-bearing (WB) conditions, are limited. Therefore, we examined the effects of real-time visual biofeedback (RVBF) of pelvic movement on electromyographic (EMG) activity of hip muscles and lateral pelvic tilt during unilateral WB and side-lying hip abductions. Fifteen male participants performed unilateral WB and side-lying hip abduction exercises with and without RVBF. Under the RVBF condition, participants monitored pelvic movements in real time during hip abduction exercises. EMG activity of Gmed and quadratus lumborum (QL) as well as lateral pelvic tilt angle were recorded during each hip abduction exercise. Gmed EMG activity increased, while lateral pelvic tilt decreased during both hip abduction exercises with RVBF (p < 0.05). Additionally, the changes in Gmed activity, the Gmed/QL activity ratio, and the lateral pelvic tilt angle under RVBF were greater during unilateral WB hip abduction than during side-lying hip abduction (p < 0.05). These results suggest that RVBF of pelvic movement could be useful to strengthen Gmed and prevent compensatory lateral pelvic movement during hip abduction exercises, especially in the unilateral WB position.

The effects of pressure biofeedback training on infraspinatus muscle activity and muscle thickness.

The aim of this study was to investigate muscle activity in the infraspinatus and posterior deltoid and infraspinatus muscle thickness during a prone external rotation (PER) exercise using pressure biofeedback. Fifteen healthy men participated in this study, performing PER exercise with pressure biofeedback under four conditions (comfortable, 2 mm Hg, 4 mm Hg, and 8 mm Hg). Surface electromyography (EMG) was used to monitor infraspinatus and posterior deltoid muscle activity, and ultrasonography was used to collect infraspinatus muscle thickness data. Infraspinatus activity and muscle thickness were greatest at 2 mm Hg pressure feedback, and both measures were significantly different from those under other pressure feedback conditions (p < 0.05). In contrast, posterior deltoid activity was lower at 2 mm Hg. However, there was no significant difference between any of the four pressure feedback conditions. These findings suggest that PER exercise with pressure biofeedback, particularly at 2 mm Hg, is effective in selectively activating the infraspinatus muscle.