Scapular muscles' activity in female volleyball players with scapular asymmetry in the resting position

Background/Aim: Resting scapular asymmetry with a more protracted and depressed position of the scapula in the dominant throwing side relative to the scapula of the contralateral side is commonly detected in overhead athletes with both healthy and disabled shoulders. It has been proposed that possible alterations in the EMG activity of periscapular muscles due to asymmetric position of the scapula may alter its kinematics leading to shoulder pathology. The aim of the current study was to identify possible alterations in the activation of periscapular muscles of healthy female volleyball players with scapular asymmetry in the resting position. Methods: Resting position of the scapula was determined in 37 healthy professional female volleyball players. Twenty-two players, with the scapula of the dominant side in a more protracted and depressed position compared to the non-dominant side, were classified as the asymmetry group. Fifteen players with almost symmetrical position of both scapulae comprised the control group. All participants performed an upper extremity closed chain exercise (knee push-ups) on a stable (floor) and an unstable surface (BOSU platform), while the EMG activity of serratus anterior (SA), upper trapezius (UT) and middle trapezius (MT) was recorded bilaterally. Results: No significant group (asymmetry vs. control) by side (dominant vs. non-dominant) by surface condition (floor vs. BOSU platform) interaction was detected with regard to the EMG activity of SA, UT and MT. Although not statistically significant the asymmetry group demonstrated a tendency for reduced EMG activity of the SA on the dominant compared to the contra-lateral side and compared to the dominant side of the control group. Conclusions: The EMG activity of periscapular muscles (SA, UT and MT) was not affected during execution of a close chain exercise in healthy female volleyball players with the scapula of the dominant side in a more protracted and depressed resting position. (C) 2017 Elsevier Ltd. All rights reserved.