Shoulder Coordination During Full-Can and Empty-Can Rehabilitation Exercises.

CONTEXT: Supraspinatus tear is a common rotator cuff injury. During rehabilitation, debate persists regarding the most appropriate exercises. Whereas shoulder coordination is part of normal arm function, it has been infrequently considered in the context of exercise selection.

OBJECTIVE

To assess shoulder-motion coordination during 2 common supraspinatus rehabilitation exercises and to characterize load and motion-direction influences on shoulder coordination.

DESIGN

Descriptive laboratory study.

SETTING

Motion-analysis laboratory. Patient or Other

Participants

Fifteen asymptomatic right-hand-dominant men (age = 26 ± 4 years, height = 1.77 ± 0.06 m, mass = 74.3 ± 7.7 kg).

INTERVENTION(S): Full-can and empty-can exercises with and without a 2.27-kg load.

MAIN OUTCOME MEASURE(S): We recorded motion with an optoelectronic system. Scapulohumeral rhythm and complete shoulder joint kinematics were calculated to quantify shoulder coordination. The effects of exercise type, load, motion direction, and humerothoracic-elevation angle on the scapulohumeral rhythm and shoulder-joint angles were assessed.

RESULTS

We observed multivariate interactions between exercise type and humerothoracic elevation and between load and humerothoracic elevation. Scapulohumeral rhythm increased by a mean ratio of 0.44 ± 0.22 during the full-can exercise, whereas the addition of load increased mean glenohumeral elevation by 4° ± 1°.

CONCLUSIONS

The full-can exercise increased the glenohumeral contribution, as hypothesized, and showed normal shoulder coordination. During the empty-can exercise, the increased scapulothoracic contribution was associated with a compensatory pattern that limits the glenohumeral contribution. Using loads during shoulder rehabilitation seems justified because the scapulohumeral rhythm is similar to that of unloaded arm elevation. Finally, motion direction showed a limited effect during the exercises in healthy individuals.