Scapular kinematics during supraspinatus rehabilitation exercise - A comparison of full-can versus empty-can techniques

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 degrees, 60 degrees, and 90 degrees 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 degrees 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.