Comparisons of electromyographic activity of scapular muscles between elevation and lowering of the arms

Abstract

The aim of this study was to compare the electromyographic (EMG) activity levels of the serratus anterior, upper, middle, and lower trapezius muscles between elevation and lowering of the arms with 10 healthy subjects. The EMGs of each muscle was quantified and normalized for the complete movement, as well as for the six different phases of each movement. Repeated measure ANOVAs were used to investigate main and interaction effects between movements/sides and sides/phases (α<0.05). Significant differences were found between the elevation and the lowering of the arms for all muscles (p≤0.001). However, there were no significant differences between sides (0.24<p<0.97), nor interactions between movements and sides (0.28<p<0.81) and between sides and phases (0.22<p<0.94) for all muscles. In addition, significant differences were found between phases for all muscles during elevation (p≤0.001) and lowering of the arms (0.001<p<0.01). Despite the different patterns of activity of all muscles, there were some similarities: For both movements, dominance of the upper extremities did not appear to be an important variable to be considered; the serratus anterior was the only muscle that showed significant differences in EMGs between all phases; and the middle trapezius was the muscle that showed the longest plateau phase.