The Effect of Glenohumeral Rotation on Scapular Upward Rotation in Different Positions of Scapular-Plane Elevation

Context: Glenohumeral and scapular upward rotation are important factors in functional upper extremity motion. Objectives: To determine how different amounts of glenohumeral rotation (internal, external, and neutral) affect scapular upward rotation. Design: Controlled laboratory study. Independent variables were the amounts of internal, external, and neutral glenohumeral rotation. The dependent variable was the amount of scapular upward rotation. Setting: Research laboratory. Participants: 40 subjects who were right-hand dominant, sedentary, and age 16 to 35 years. Main Outcome Measures: An inclinometer assessed scapular upward rotation with the 3 different positions of glenohumeral rotation in each 0°, 30°, 60°, and 90° of humeral elevation in the scapular plane. Results: Scapular upward rotation tended to increase with glenohumeral internal and external rotation, compared with neutral rotation in each degree of humeral elevation. This trend was seen on both right and left sides. Conclusions: Scapular upward rotation at different levels of humeral elevation in the scapular plane was affected by the positions of glenohumeral rotation.