Effects of lumbar stabilization using a pressure biofeedback unit on muscle activity and lateral pelvic tilt during hip abduction in sidelying.

OBJECTIVE

To assess the effects of lumbar spine stabilization using a pressure biofeedback unit on the electromyographic activity and angle of lateral pelvic tilt during hip abduction in a sidelying position.

DESIGN

Comparative, repeated-measures study.

SETTING

University research laboratory.

PARTICIPANTS

Eighteen able-bodied volunteers (9 men, 9 women) with no history of pathology.

INTERVENTION

Subjects were instructed to perform hip abduction in a sidelying position in both the preferred hip abduction (PHA) and hip abduction with lumbar stabilization (HALS). A pressure biofeedback unit was used for lumbar stabilization.

MAIN OUTCOME MEASURES

Surface electromyography was recorded from the quadratus lumborum, gluteus medius, internal oblique, external oblique, rectus abdominis, and multifidus muscles. Kinematic data for lateral pelvic tilt angle were measured using a motion analysis system. Dependent variables were examined with 2 (PHA vs HALS) x 2 (men vs women) analysis of variance.

RESULTS

Significantly decreased electromyographic activity in the quadratus lumborum (PHA, 60.39% +/- 15.62% of maximum voluntary isometric contraction [MVIC]; HALS, 27.90% +/- 13.03% of MVIC) and significantly increased electromyographic activity in the gluteus medius (PHA, 25.03% +/- 10.25% of MVIC; HALS, 46.06% +/- 21.20% of MVIC) and internal oblique (PHA, 24.25% +/- 18.10% of MVIC; HALS, 44.22% +/- 20.89% of MVIC) were found when the lumbar spine was stabilized. Lateral pelvic tilt angle (PHA, 13.86 degrees +/- 4.66 degrees; HALS, 5.55 degrees +/- 4.16 degrees) was decreased significantly when the lumbar spine was stabilized. In women the electromyographic activity (percentage of MVIC) in gluteus medius, external oblique, and rectus abdominis was significantly higher than that observed in men.

CONCLUSIONS

With lumbar stabilization, the gluteus medius and internal oblique activity was increased significantly, and the quadratus lumborum activity was decreased significantly, causing reduced lateral pelvic tilt in a sidelying position. These results suggest that hip abduction with lumbar stabilization is useful in excluding substitution by the quadratus lumborum.