Effectiveness of the EMG activity of the gluteus maximus and multifidus muscles during prone hip extension according to shoulder muscle co-activation

This study examined the effects of the activation of shoulder muscles on the electromyography (EMG) activity of the posterior oblique sling (POS) muscles during prone hip extension (PHE). Ten healthy males were recruited. PHE with activation of different shoulder muscles were performed in randomized order: the latissimus dorsi (LD) and middle trapezius (midT). Surface EMG signals were recorded for the LD and midT (contralateral) and for the lumbar multifidus (MF) (bilateral), gluteus maximus (GM), and biceps femoris (BF) (ipsilateral). The bilateral MF and ipsilateral GM EMG amplitudes were greatest during PHE with activation of the midT, followed by PHE with activation of the LD (p < 0.05). The BF amplitude during PHE with activation of the LD was greater than that during PHE with activation of midT (p < 0.05). PHE with activation of the midT, which is aligned with the POS, increased the activation of lumbopelvic muscles such as the MF and GM.