Activation of upper limb muscles in subjects with scapular dyskinesis during bench-press and dumbbell fly on stable and unstable surfaces

Abstract

Scapular dyskinesis has been associated with shoulder dysfunctions, and changes in electromyographic (EMG) activity have been reported during the execution of some exercises. To compare upper limb muscles EMG of asymptomatic subjects with and without scapular dyskinesis during bench-press and dumbbell fly exercise performed on different surface stability conditions. Twenty-eight physically active men were allocated into two groups: Control group (n= 14) and Dyskinesis group (n= 14). The participants performed six repetitions lasting three seconds of the bench press and dumbbell fly exercises with 50% of one-repetition maximum (1RM) on a bench and a Swiss ball. The EMG activity of the pectoralis major, serratus anterior, upper and lower trapezius, anterior deltoid, biceps and triceps muscles were recorded. No differences were found between groups, regardless of exercise or surface type. Inserting the unstable surface in the supine exercise promoted a slight increase in upper trapezius EMG activity for the control [4.32 (95% CI: 1.04 to 7.60)] and dyskinesis [3.30 (95% CI: 0.34 to 6.27)] groups. There is no difference in upper limb muscle EMG activity between subjects with and without scapular dyskinesis. In addition, inserting unstable surfaces did not modify EMG activity.