The effect of limb support on muscle activation during shoulder exercises.

The purpose of this study was to determine the difference in demands on glenohumeral musculature during unsupported and supported active range-of-motion (AROM) shoulder exercises. Twenty healthy subjects volunteered for this study. Surface or fine-wire bipolar electrodes were applied to the infraspinatus, posterior deltoid, anterior deltoid, pectoralis major, and supraspinatus muscles. Subjects performed vertical wall slides and diagonal wall slides (45 degrees angle) with their hand in contact with the wall (supported) and not in contact with the wall (unsupported). Significantly greater supraspinatus activity was found in the unsupported exercises versus the supported exercises (F(4,76) = 4.38, P = .003). Exercises performed in the 45 degrees diagonal position were more demanding on shoulder musculature than vertical exercises (F(1,19) = 19.3, P < .001). Although our results were obtained in healthy subjects and the implications in a pathological population are not clear, we suggest that when designing a progression of exercises for increasing shoulder muscular activity, supported short lever arm AROM exercises should precede unsupported long lever arm AROM exercises.