Electromyography of the coracobrachialis—Construct validity and implications for rehabilitation of anterior shoulder dislocation

Background: The coracobrachialis (CB) is an important anterior shoulder stabilizer, yet no study has previously reported its electromyography (EMG). The purpose of this study was to validate a novel technique for surface EMG (sEMG) of the CB. Methods: Thirty-two (21 females) healthy individuals participated in this cross-sectional study. A surface landmark for recording the CB was identified within the medial aspect of the proximal arm using real-time ultrasound imaging and cadaver dissection. The EMG from this landmark as well as from the biceps brachii (BB) were simultaneously recorded during shoulder horizontal adduction (SHAd) (a CB-dominant test), and during elbow flexion (EFlx) and forearm supination (FSup) (BB-dominant tests). Differences between CB and BB activation (% maximal voluntary isometric contraction) within each test were assessed. Results: CB activation was significantly greater than BB during SHAd (36.51% versus 4.09%, P < 0.001). BB activation was significantly greater than CB during FSup (34.85% versus 27.70%, P = 0.045). No difference between CB and BB activation was noted during EFlx (41.82% versus 28.64%, P = 0.061). Conclusions: The moderate activation of the CB with simultaneous minimal activation of the BB during SHAd supports this novel sEMG technique. This technique may assist the design of exercises to train the CB. Level of evidence: III.