title: Change in glenohumeral rotation and scapular position after a Division I collegiate baseball season.
abstract: BACKGROUND
  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.
  
  
  METHODS
  Pretest to posttest study.
  
  
  METHODS
  Controlled laboratory setting.
  
  
  METHODS
  Thirty-one collegiate baseball players with no current shoulder or elbow injury completed this study.
  
  
  METHODS
  Participants were measured for all dependent variables at preseason and postseason.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Dept of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Stephen John
authors.initials: SJ
authors.lastname: Thomas
authors.forename: Charles B
authors.initials: CB
authors.lastname: Swanik
authors.forename: Kathleen
authors.initials: K
authors.lastname: Swanik
authors.forename: John D
authors.initials: JD
authors.lastname: Kelly
mesh_terms: D000328:Adult; D001484:Baseball / Q000502:physiology*; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D016059:Range of Motion, Articular / Q000502:physiology*; D012399:Rotation; D012540:Scapula / Q000503:physiopathology*; D012785:Shoulder Joint / Q000503:physiopathology*