Activity of the quadratus lumborum and trunk muscles relates to pelvic tilt angle during pelvic tilt exercises.

OBJECTIVES Pelvic tilt exercises are used clinically to correct lumbo-pelvic alignment. The anterior (QL-a) and posterior (QL-p) layers of the quadratus lumborum are important for pelvic motor control in the coronal plane. This study aimed to evaluate whether the QL-a and QL-p activity is related to the pelvic tilt angle during pelvic tilt exercises. DESIGN The study design was single-occasion repeated measures in a randomized manner. Twelve healthy men performed the four directions of the pelvic tilt exercises (anterior or posterior pelvic tilt and lateral pelvic elevation on the ipsilateral or contralateral measurement side). The electromyographies of the QL-a and QL-p were recorded using intramuscular fine-wire electrodes and normalized to isometric peak electromyography. RESULTS The activity of the QL-a and QL-p during lateral pelvic elevation on the ipsilateral measurement side (19.0±16.0 %MVIC) was significantly higher than that during other directions of the pelvic tilt exercises (P<0.01). There was a significant positive correlation between the QL-a activity and the maximum change angles of pelvic tilt during lateral pelvic elevation on the ipsilateral measurement side (r=0.674, P=0.016). CONCLUSIONS The QL-a activity was related to a large lateral pelvic elevation angle on the ipsilateral side during pelvic tilt exercises.