Scapular muscle recruitment patterns and isokinetic strength ratios of the shoulder rotator muscles in individuals with and without impingement syndrome

The aim of this study was to compare the recruitment patterns and latencies of the scapular muscles, as well as the isokinetic performance of the shoulder rotators in 10 subjects with unilateral impingement syndrome who comprised the impingement group (IG) with a control group (CG) of 10 asymptomatic subjects. The recruitment patterns and latencies were evaluated by electromyographic activity during arm elevation in the scapular plane. Isokinetic work ratios of the shoulder rotator muscles were used to analyze muscular performance. A 2 x 2 ANOVA detected that muscular performance and recruitment patterns were similar for both groups and sides. However, the ANOVA revealed a significant side and group interaction, indicating that the scapular muscle latencies of the affected shoulder was greater than that of the nonaffected side only for the IG (p < .001). These findings indicated that subjects with light to moderate impingement syndrome showed late recruitment of the scapular muscles during arm elevation. However, muscular performance of the shoulder rotator muscles was not affected.