Effect of Shoulder Abduction Angles on EMG Activity of the Abdominal Muscles during Single Leg Holding on the Foam Roller

Abstract

Purpose: This study examined the electromyography (EMG) activity of the abdominal muscles and the ratio of the oblique abdominal muscle activity to the rectus abdominis muscle during a single-leg holding position with isometric shoulder abduction (SLHISA) in the supine position on a foam roller. Methods: Nineteen healthy males were recruited to the study. Each subject was asked to lay on a round foam roller and perform single-leg (nondominant) holding with contralateral shoulder abduction to one of three angles (45°, 90°, or 135°) in random order. The surface EMG signals of the bilateral rectus abdominis (RA), external oblique abdominis (EO), and combined internal oblique abdominis (IO) and transverse abdominis (TrA) muscle were collected during the tasks. The EO/RA and (IO & TrA)/RA ratios were determined using surface EMG. One way repeated measure ANOVA with three SLHISAs was used to assess the significant abdominal muscle EMG activity and the ratio of the oblique abdominal muscles activity to the RA muscle. The statistical significance level was p<0.05. Results: The results were as follows. The SLHISA 135° showed significantly higher EMG activity of both RAs, left EO, and right IO & TrA muscles (p<0.05). The right EO and left IO and TrA muscles/RA were significantly different among the SLHISA angles. The SLHISA 45° showed a significantly greater ratio of right EO/RA and left IO & TrA/RA (p<0.05). Conclusion: SLHISA on a foam roller is useful for lumbopelvic stabilization exercise by increasing the activity and recruiting a specific pattern of the oblique abdominal muscle.