Shoulder EMG during depression raise in men with spinal cord injury: the influence of lesion level.

BACKGROUND & OBJECTIVE: The depression-style raise maneuver is commonly performed by persons with spinal cord injury (SCI) to relieve skin pressures and avoid skin ulceration. The demands of this critical activity, however, are not fully documented for individuals with higher spinal cord lesions. The purpose of this investigation was to determine the influence of SCI lesion level on shoulder muscle activity during a depression raise maneuver.

EXPERIMENTAL DESIGN

Sample of convenience, group comparison.

METHODS

Fine-wire intramuscular electrodes recorded electromyographic (EMG) activity from 12 shoulder muscles in 57 men with SCI while they performed depression raises (C6 tetraplegia, n = 10; C7 tetraplegia, n = 18; high paraplegia, n = 16; low paraplegia, n = 13). EMG intensity was normalized to a manual muscle test (MMT) effort.

RESULTS

For persons with paraplegia and C7 tetraplegia, dominant EMG activity was recorded from latissimus dorsi, sternal pectoralis major, and triceps muscles (31%-69% MMT). Tetraplegic groups had significantly greater anterior deltoid activity (C6 = 53%, C7 = 22% MMT) than that recorded in paraplegic groups (high paraplegia = 10%, low paraplegia = 3% MMT). Participants with tetraplegia also had increased infraspinatus activity (C6 = 50%, C7 = 32% MMT) compared with participants with low paraplegia (7% MMT). All other muscles had low or very low EMG activity during the depression raise.

CONCLUSIONS

Persons with tetraplegia lack normal strength of the primary muscles used by participants with paraplegia for the depression raise (ie, latissimus dorsi, sternal pectoralis major, and triceps muscles). Although increased anterior deltoid activation assisted with elbow extension, it potentially contributes to glenohumeral joint impingement. Alternate methods of pressure relief should be considered for persons with tetraplegia.