Effects of pressure biofeedback application location for subjects with lumbar instability on pelvic rotation and hip joint abductor muscle activity during the Clam exercise.

Objective: The purpose of this study was to find out how the back instability during clam exercise (CE) causes changes in pelvicrotation and hip joint abductor muscle activity, and to find out the effects with different methods of application of pressurebiofeedback. Design: Comparative study using repeated measures. Methods: Each subjects performed the clam exercise (CE) without pressure biofeedback, the clam exercise with pressurebiofeedback applied to the back (CE-PBU to back), and the clam exercise with pressure biofeedback applied to the side (CE-PBUto side). The amount of pelvic rotation was measured using myomotion. And the muscle activity of the muscle gluteus medius andthe tensor fasciae latae was measured using EMG device. One-way repeated measures ANOVA followed by the Bonferroni posttest were used to compare the EMG activity in each muscle and pelvic rotation angle during the CE, CE-PBU to back, CE-PBU toside. Results: The amounts of pelvic rotation was the lowest in CE-PBU to back (p< 0.05) and the ratio of muscle activity of the musclegluteus / tensor fasciae latae was the highest in CE-PBU to back (p< 0.05). Conclusions: It is thought that, in order to stabilize the waist-pelvis and increase hip joint muscle strength in subjects with backinstability, applying clam exercise with pressure biofeedback applied to the lower back is effective in improving waist-pelvicmovements and selectively strengthening the muscle gluteus medius.