Lower Trapezius Activity During Supported and Unsupported Scapular Retraction Exercise

Abstract

Introduction: Rehabilitation protocols often recommend avoiding concentric strengthening of the repaired rotator cuff muscle(s), and many of the scapulothoracic muscles such as the trapezius, until the sixth week after surgery (Ciullo 1996). Avoidance of exercising the repaired rotator cuff muscle(s) during this time period may be logical, however, avoidance of exercising the non-injured scapulothoracic musculature is not. Although exercises to strengthen scapulothoracic muscles have been examined (Moseley et al., 1992), few studies have explored an effective technique for strengthening the lower trapezius in a range of motion available to post-operative rotator cuff repair patients. Therefore, the purpose of this investigation was to determine if the lower trapezius muscle responds to scapular retraction exercise in ranges of motion available to rotator cuff repair patients during the early stages of rehabilitation. Methods: Twelve women and eight men free of rotator cuff pathology volunteered as subjects (Mage = 26.9 ± 5.9 yrs). Participants engaged in three separate scapular retraction exercises performed in the scapular plane with the arms supported in 90°, 120° and with the arms unsupported in 130° (Figure 1). Surface electrodes were placed on the skin over the middle deltoid, lower trapezius, upper trapezius, and infraspinatus muscles. For each condition three trials of EMG data were sampled at 1000 Hz, full wave rectified, and integrated over a 4 s time period. The calculated mean EMG value was compared between conditions using a repeated-measures analysis of variance with an alpha set at the .01 level.Figure 1: Arm positions for scapular retractionResults: The results indicated that mean EMG values for lower trapezius, infraspinatus, deltoid, and upper trapezius muscles were greater for the 130° versus both the 90° and 120° conditions. Additionally, the deltoid muscle exhibited a greater value for the 120° versus 90° condition (Table 1).Table 1: Mean (± SD) EMG values (mV s) during scapular retraction exerciseDiscussion: The results of this study are in agreement with Moseley et al. (1992) who found the lower trapezius muscle to be most active in the 120° - 150° range during various rehabilitation exercises that involve scapular retraction. Our results add to this knowledge base by showing the lower trapezius muscle to be active during scapular retraction exercises in ranges of motion attainable by acute rotator cuff repair patients (i.e., 90°). Our results further indicate that the 90° scapular retraction exercise as compared to the 120° and 130° conditions may put less tension on select rotator cuff muscles because the infraspinatus muscle was less active during the 90° condition. In conclusion, these findings suggest that supported scapular retraction at 90° may be an effective exercise to perform with post-operative rotator cuff repair patients during the early stages of recovery. This exercise may enhance early scapular upward rotation leading to early restoration of shoulder flexion and abduction ranges of motion.