The Relationship between Scapular Protraction and Posterior Shoulder Tightness among Baseball Players

Abstract

Excessive and untimely scapular protraction during the throwing motion has been associated with several shoulder injuries. Since the scapula provides attachment of a number of posterior soft tissue structures in the shoulder, many have hypothesized that posterior shoulder tightness may alter proper scapular kinematics. PURPOSE: To examine the correlation between scapular protraction and posterior shoulder tightness and rotational range of motion (ROM), as well as to investigate whether or not any differences exist in scapular protraction between baseball pitchers and position players. METHODS: Twenty professional baseball pitchers (age=22.6±3.6 years, height=188.4±4.6 cm, mass=93.3±7.9 kg) and 20 position players (age=22.3±2.3 years, height=181.7±5.2 cm, mass=88.0±8.5 kg) with no recent history of upper extremity injury participated in this study. We tested bilateral scapular protraction using the double square method. We measured glenohumeral (GH) horizontal adduction ROM, and internal rotation and external rotation ROM with a digital inclinometer, while the subjects were in a supine position with their scapula stabilized. RESULTS: A multiple regression analysis showed a moderate-to-good negative relationship between GH horizontal adduction ROM and scapular protraction (r2=.50, P=.001). T-tests demonstrated that the dominant shoulders of both pitchers (170.7±9.1 mm) and position players (165.4±8.3 mm) had significantly more scapular protraction compared to their non-dominant shoulders (pitchers: 163.1±10.5 mm, position players: 157.7±11.0 mm) (P<.004). Furthermore, the dominant shoulders of the pitchers had significantly more scapular protraction compared to the position players (P=.03). There were no other significant relationships or differences found for any other variables (r2<.04, P>.15). CONCLUSIONS: There was a moderate-to-good relationship between posterior shoulder tightness and scapular protraction. Furthermore, baseball players had significantly more scapular protraction of the dominant arm compared to their non-dominant arm, while pitchers had more scapular protraction of their dominant arm compared to position players. This study was funded by a grant from the Illinois Association for Health, Physical Education, Recreation and Dance.