Investigation of the effect of oscillation exercises applied in different shoulder positions on shoulder muscle activation in individuals with and without rotator cuff tendinosis

This study was performed to investigate the effect of the activation of the upper trapezius (UT), lower trapezius (LT), infraspinatus (IS), middle deltoid (MD) and serratus anterior (SA) muscles during oscillation exercises in different shoulder positions and different grip patterns between individuals with rotator cuff tendinosis and healthy individuals. Eighteen (9 female, 9 male) healthy individuals and 18 (9 female, 9 male) individuals with rotator cuff tendinosis between the ages of 18-45 were included in the study according to the results of ultrasonography and clinical test performed by the physician. Surface electromyography (EMG) was used to evaluate muscle activation. Oscillation exercises were performed in 0˚ abduction, scapular elevation, 90˚ flexion and 90˚ abduction positions. Different grip patterns were used in the 90˚ abduction position. The upper trapezius/lower trapezius (UT/LT), upper trapezius/serratus anterior (UT/SA) and middle deltoid/infraspinatus (MD/IS) force couple ratios were investigated in different shoulder positions and different grip styles. Muscle activations and force couple ratios were similar between the groups (p>0.05). Differences were found between muscle activations and force couple ratios in different shoulder positions and different grip styles (p<0.05). Activation of all muscles was lower in the 0˚ abduction position compared to the other positions. UT, LT and MD muscle activations were the highest in the 90˚ abduction position, whereas IS and SA muscle activations were the highest in the 90˚ flexion position. In this regard, we think that the oscillation exercises in our study can be adapted to both individuals with rotator cuff tendinosis and healthy individuals. This study may guide the exercise progression of individuals with rotator cuff tendinosis with high physical activity level. Key words: Rotator cuff, tendinosis, oscillation, electromyography.