title: Internal rotation and scapular position differences: a comparison of collegiate and high school baseball players.
abstract: BACKGROUND
  Conditions such as labral and rotator cuff injuries have been linked with decreases in glenohumeral internal-rotation and increases in external-rotation motion. Also, decreased glenohumeral internal rotation is strongly associated with scapular dyskinesis.
  
  
  OBJECTIVE
  To compare healthy collegiate and high school baseball players' glenohumeral joint range of motion and scapular position.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  Institutional research laboratory.
  
  
  METHODS
  Thirty-one male National Collegiate Athletic Association Division I collegiate (age = 20.23 +/- 1.17 years, height = 186.24 +/- 5.73 cm, mass = 92.01 +/- 7.68 kg) and 21 male high school baseball players (age = 16.57 +/- 0.76 years, height = 180.58 +/- 6.01 cm, mass = 79.09 +/- 11.51 kg).
  
  
  METHODS
  Glenohumeral internal and external rotation and scapular upward rotation were measured with a digital inclinometer. Scapular protraction was measured with a vernier caliper. All variables except scapular upward rotation were calculated as the difference between the dominant and nondominant sides.
  
  
  RESULTS
  Collegiate baseball players had more glenohumeral internal-rotation deficit (4.80 degrees, P = .028) and total motion deficit (5.73 degrees, P = .009) and less glenohumeral external-rotation gain (3.00 degrees, P = .028) than high school players. Collegiate baseball players had less scapular upward rotation than high school players at the 90 degrees (4.12 degrees, P = .015, versus 3.00 degrees, P = .025) and 120 degrees (4.00 degrees, P = .007, versus 3.40 degrees, P = .005) positions. The scapular protraction difference was greater in collegiate baseball players than in high school players in the hands-on-hips and 90 degrees positions (0.77 cm, P = .021, and 1.4 cm, P = .001).
  
  
  CONCLUSIONS
  When comparing high school with collegiate baseball players, these data suggest that glenohumeral internal-rotation deficit and scapular position change as the level of competition increases.
authors.affiliation: University of Delaware, Newark, DE, USA. sjthomasatc@gmail.com
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Thomas
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: Swanik
authors.forename: Charles B
authors.initials: CB
authors.lastname: Swanik
authors.forename: John D
authors.initials: JD
authors.lastname: Kelly
mesh_terms: D000704:Analysis of Variance; D001265:Athletic Injuries / Q000209:etiology; D001484:Baseball / Q000293:injuries / Q000502:physiology*; D003430:Cross-Sectional Studies; D006801:Humans; D008297:Male; D015999:Multivariate Analysis; D011187:Posture; D016059:Range of Motion, Articular; D017006:Rotator Cuff / Q000502:physiology; D000070636:Rotator Cuff Injuries; D012540:Scapula / Q000293:injuries / Q000502:physiology; D012574:Schools; D000070599:Shoulder Injuries; D012785:Shoulder Joint / Q000502:physiology*; D013334:Students; D014495:Universities; D055815:Young Adult