Muscle Synergies of The Butterfly Stroke: Comparison Between A History of Shoulder Pain During Swimming

This study aimed to investigate whether muscle coordination differs between swimmers with and without a history of swimmer's shoulder (SS). Muscle synergies, which can assess muscle coordination, in young elite male swimmers were analyzed using surface electromyography (EMG). Twenty elite swimmers who swam the butterfly stroke were included in this study (SS n=8; control n=12). Four muscle synergies in both groups were identified. Synergy #1, which is involved in the early pull, and Synergy #3, which is involved in the early recovery, were shown to be different synergies in both groups. In the SS group, the contribution of the internal oblique, external oblique, and rectus abdominis, which are involved in stabilizing the trunk, was low during the early pull. In the early recovery, the SS group had lower contributions of the serratus anterior, upper trapezius, and lower trapezius involved in stabilizing the shoulder girdle, and a lower contribution of the erector spinae presenting in the control group. In the rehabilitation is desirable to introduce exercises to obtain coordination of the upper limb and abdominal muscles in the early pull phase, and coordination of the periscapular muscles and erector spinae in the early recovery phase.