The trapezius and serratus anterior are very important muscles of the shoulder girdle in that they perform upward rotation and stabilized of the scapula. Any weakness of these muscles is believed to affect the scapulohumeral rhythm that may cause secondary problems at the glenohumeral joint. There is very little information in the literature regarding electromyography analysis of muscle testing or exercises for the trapezius and serratus anterior muscles. The purposes of this study were to: 1) perform an electromyographic analysis of manual muscle testing positions for the trapezius and serratus anterior muscles to help identify which tests are optimal for clinical muscle testing and for normalization procedures during EMG studies, 2) perform an electromyographic study during strengthening exercises for the trapezius and serratus anterior muscles to determine which exercises produce maximum electromyographic activity, and 3) compare the torque measurements obtained during hand-held dynamometry muscle testing of the trapezius and serratus anterior muscles of the dominant and non-dominant shoulders and identify which muscle tests can be reliably performed with a hand-held dynamometer.
