Change in glenohumeral rotation and scapular position after a Division I collegiate baseball season.

CONTEXT Pathologies such as anterior instability and impingement are common in baseball and have been linked to decreases in internal-rotation (IR) motion and concurrent increases in external-rotation (ER) motion. In addition, alterations to scapular upward rotation have been identified in this population. OBJECTIVE To measure glenohumeral (GH) IR and ER rotation, total range of motion (ROM), and scapular upward rotation throughout the course of a Division I collegiate baseball season. DESIGN Pretest to posttest study. SETTING Controlled laboratory setting. PARTICIPANTS Thirty-one collegiate baseball players with no current shoulder or elbow injury completed this study. INTERVENTION Participants were measured for all dependent variables at preseason and postseason. MAIN OUTCOME MEASURES GH IR and ER were measured supine with the scapula stabilized. Total GH ROM was calculated as the sum of IR and ER measures. Scapular upward rotation was tested at rest, 60°, 90°, and 120° of GH abduction in the scapular plane. RESULTS Overall, the dominant arm had significantly less GH IR and significantly more ER than the nondominant arm. The total motion on the dominant arm was significantly less than on the nondominant arm. No significant differences were observed from preseason to postseason for IR, ER, or total motion. Dominant-arm scapular upward rotation significantly decreased at 60°, 90°, and 120° of abduction from preseason to postseason. CONCLUSION Collegiate baseball players presented with significant GH-motion differences (decreases in IR and increases in ER) in their dominant arm compared with their nondominant arm. There was also significantly less total motion on the dominant arm. After 12 wk of competitive Division I collegiate baseball, there were significant decreases in upward rotation over the season.