Radiographic analysis of commonly prescribed scapular exercises

HypothesisThe performance of scapular exercises in the context of a clinical model of fatigue will result in superior migration of the humeral head and alterations in shoulder kinematics on radiographic analysis.Materials and methodsSix healthy male volunteers underwent a series of radiographs before and immediately following two scapular exercises. To reproduce a practice setting a clinical model of muscle fatigue was utilized. Radiographs were taken at various degrees of elevation. Glenohumeral angle (GA), scapulothoracic angle (SA), and the position of the humeral head on the glenoid (excursion) were measured on each radiograph. Two-tailed paired sample t-test were used to compare pre-fatigue to post fatigue measures.ResultsFollowing fatigue there was a significant increase in excursion at 45, 90, and 135 degrees of elevation indicating superior migration of the humeral head. There was an increase in SA from 0 to 45 degrees and a decrease in GA from 45 to 90 degrees of elevation. From 90 to 135 degrees an increase in GA was observed.DiscussionThe amount of superior migration of the humeral head observed following exercise was consistent with previously reported amounts of superior migration in patients with subacromial impingement. The alterations that occurred in shoulder kinematics following exercise may have resulted from parascapular muscle fatigue as well as rotator cuff muscle insufficiency.ConclusionIn the context of a clinical model of fatigue, these scapular exercises resulted in superior migration of the humeral head and alterations in shoulder kinematics on radiographic analysis in healthy subjects.Level of evidenceBasic science study.