Scapular Kinematics during Supraspinatus Rehabilitation Exercise

Abstract

Background Supraspinatus strengthening is an important component of shoulder rehabilitation. Previous work has determined that the full-can and empty-can exercises elicit the greatest amount of supraspinatus activity. However, scapular kinematics has not been considered when prescribing supraspinatus exercises. Hypothesis Scapular downward rotation, internal rotation, and anterior tipping during the empty-can exercise are increased when compared with the full-can exercise. Study Design Descriptive laboratory study. Methods Twenty participants performed full-can and empty-can exercises while an electromagnetic tracking system was used to collect three-dimensional scapular kinematic data. Scapular angles at 30 °, 60 °, and 90 ° of the ascending and descending phases of humeral elevation were compared using 2-way repeated measures analysis of variance. Results There was more scapular anterior tipping and internal rotation during the empty-can exercise at all sampled humeral elevation angles except at 30 ° of the descending phase for anterior/posterior tipping (P< .05). Conclusion Scapular anterior tipping and internal rotation are increased during the empty-can exercise, whereas scapular upward rotation was not different between exercises. Clinical Relevance Increased scapular internal rotation and anterior tipping decrease the volume of the supraspinatus outlet during the empty-can exercise. When maintenance of the subacromial space is important, use of the full-can exercise seems most appropriate for selective strengthening of the supraspinatus muscle.