Context: Changes to the shoulder complex, such as postural impairment, muscle length and scapular dyskinesis, have been associated with shoulder injuries in overhead athletes. It is unknown if some amount of change in shoulder kinematics is normal as a result of participating in an overhead sport regardless of the presence of shoulder injury. Objective: To compare bilateral scapular upward rotation, anterior scapular position, glenohumeral internal rotation and glenohumeral external rotation in healthy elite volleyball players prior to pre-season. Design: Within subject. Setting: Controlled laboratory environment. Patients or Other Participants: Fifteen female collegiate volleyball athletes (19.0± 1.2 y, 175.4±5.5 cm, 71.5±9.2 kg) with no history of shoulder injury participated in this study. Interventions: Static scapular upward rotation was measured at rest, 60°, 90° and 120° of humeral elevation in the scapular plane with an electrical inclinometer. Anterior scapular position was measured using the pectoralis minor length test. While the subject laid in a supine position, the distance in centimeters from the table to the posterior aspect of the acromion process was measured with a modified triangle. For glenohumeral internal rotation and external rotation, subjects laid in a supine position with the shoulder abducted to 90 and the elbow flexed to 90°. Maximum passive glenohumeral internal rotation and glenohumeral external rotation were measured with a digital protractor placed in-line with the olecranon process and ulnar styloid process. Three trials were performed on the dominant and non-dominant arms for all measurements. The average of the three trials for each measurement was calculated. The side and order of measurements were randomized. The independent variable was side (dominant and non-dominant). Main Outcome Measures: The dependant variables were the bilateral mean measurements for scapular upward rotation at rest, 60°, 90° and 120°, anterior scapular position, glenohumeral internal rotation and glenohumeral external rotation. The influence of side for each dependent variable was compared using paired samples t-tests with an adjusted alpha level (p<0.007). Results: Statistical analysis revealed anterior scapular position (t14=3.646; p=0.003) was significantly greater on the dominant side (5.9±1.1cm) compared to the non-dominant side (5.0±1.2cm). Gleno-humeral internal rotation (t14= -3.689; p=0.002) was significantly greater on the non-dominant side (74.6±7.2°) compared to the dominant side (66.2± 8.2°). There were no significant differences for glenohumeral external rotation (t14= 1.212; p=0.245) or scapular upward rotation at rest (t14=1.417; p=0.178), 60 (t14=0.075; p=0.942), 90 (t14=-0.205; p=0.840) and 120 (t14=0.590; p= 0.564). Conclusions: Bilateral differences in anterior scapular position and glenohumeral internal rotation were evident. Measurements were taken on healthy participants prior to pre-season. It is possible these kinematic differences are normal adaptations associated with participation in an overhead sport or precursors to shoulder injury. A longitudinal study where shoulder kinematics of overhead athletes are tracked over the ourse of a season is warranted.
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