Electromyographic analysis of the shoulder muscles during depression transfers in subjects with low-level paraplegia

Objective: To document and compare the intensity of selected shoulder muscle activity during depressionn transfers. Design: Intramuscular electrodes were used to record the activity of 12 shoulder muscles while transferring to and from a wheelchair. Participants: Twelve adult men with spinal cord injuries resulting in low paraplegia. Outcome Measures: Three phases of the transfer were analyzed: preparation, lift, and descent. Median intensities were compared between muscles, transfer phase, and direction of transfer using Freidman's test. Results: Trunk elevation was accomplished mainly by sternal pectoralis major and latissimus dorsi activity. Lateral body displacement required other muscles to control the elevated body. Rotator cuff muscles contributed to shift mechanics and, together with anterior deltoid, provided anterior glenohumeral wall protection. Lower serratus anterior stabilized the scapulothoracic articulation and contributed to the lateral movement. Conclusions: Assessment of depression transfer skill should not be based solely on the ability to lift body weight. Movement of the trunk required vigorous activity of key shoulder musclature. Differences in leading and trailing arm EMG intensities will assist in modifying transfer style in individuals with weakness, strength imbalances, and shoulder pathologies.