Comparison of the electromyographic recruitment of the posterior oblique sling muscles during prone hip extension among three different shoulder positions

Objective: We examined the effects of three different shoulder positions on the electromyography (EMG) activity of the posterior oblique sling and pelvic rotational angle during right prone hip extension (PHE). Methods: Fifteen healthy males (mean age, 25.4???1.2?years) participated in this study. Three different left shoulder positions (0?, 90?, 125? of abduction) were assessed during right PHE. Surface EMG signals were recorded for the left latissimus dorsi, left middle trapezius, left lower trapezius, lumbar multifidus, right gluteus maximus, and right biceps femoris. An electromagnetic tracking motion analysis device was used to monitor compensatory pelvic rotation during right PHE. Significant differences in muscle activity and pelvic rotation angle among the three different shoulder abductions were assessed using one-way repeated measures analysis of variance and the Bonferroni post hoc test. Results: The bilateral multifidus and right gluteus maximus EMG amplitudes increased with increasing shoulder abduction angle during PHE (p(adj) < 0.01). The degree of pelvic rotation during PHE decreased with increasing shoulder abduction angle (p(adj) < 0.01). Conclusions: We found that PHE with 125? of left shoulder abduction increased the selective activation of lumbopelvic stabilizing muscles such as the multifidus and gluteus maximus.