Scapular dyskinesis and overhead athletes: A systematic review of electromyography studies.

OBJECTIVE: Understanding how the main scapular muscles behave in overhead athletes with scapular dyskinesis (SD). DESIGN: Systematic Review. SETTING: Electronic searches were performed in Pubmed (MedLine), Embase, CINAHL, and SPORTDiscus databases. PARTICIPANTS: Overhead athletes with SD. MAIN OUTCOME MEASURES: Electromyographic activity of the upper (UT), middle (MT), and lower (LT) trapezius, and serratus anterior (SA). RESULTS: Eight studies were included in this review. The UT activity showed a tended to increase its activity mainly during tasks over 90° compared to 45°. SA activity had similar behavior, mainly during isometric tasks. The MT also increased its activity mainly in tasks with overhead angulations when compared to lower angulations. The LT activation tended to decrease its EMG activity at angulations below 60° in overhead athletes with SD. CONCLUSIONS: The EMG behaviour of UT and SA for non-athletes appears to differ from what has already been described in the literature. The MT seems to be the most neglected muscle for scapular stabilization in overhead athletes with SD. The decrease in LT activity suggests that this may have implications for the performance of these athletes.