Internal rotation and scapular position differences: a comparison of collegiate and high school baseball players.
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.
Thomas
Stephen J
SJ
University of Delaware, Newark, DE, USA. sjthomasatc@gmail.com
Swanik
Kathleen A
KA
Swanik
Charles B
CB
Kelly
John D
JD
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