Effect of pelvic stabilization and hip position on trunk extensor activity during back extension exercises on a Roman chair.

OBJECTIVE To assess the effect of pelvic stabilization and hip position on the electromyographic activity of trunk extensors during Roman chair exercise. A secondary objective was to compare genders. DESIGN Repeated measures. SUBJECTS Eleven men and 11 women volunteers. METHODS Five trunk flexion-extension cycles for 3 Roman chair conditions: (i) pelvis unrestrained; (ii) pelvis restrained; and (iii) hip at 40 degrees flexion. Electromyographic signals were recorded on the back muscles, as well as on the gluteus maximus and biceps femoris. The percentage of electromyographic amplitude relative to the maximal activity was used to assess the level of muscular activation of each muscle group across the exercises. RESULTS For both genders, the Roman chair conditions did not influence the activity of the back and gluteus muscles. The hip-at-40 degrees-flexion condition significantly reduced the activity of the biceps femoris (average of 4-18%) relative to the other 2 conditions. Gender differences were observed on the activity of the biceps femoris in all Roman chair conditions. CONCLUSION The hip-at-40 degrees-flexion condition would allow the Roman chair exercise to train the targeted back muscles more specifically by overloading them over a longer duration in order to induce physiological changes.