Background: Although overhead throwing athletes may develop unique glenohumeral range of motion characteristics, to our knowledge these characteristics have not been studied longitudinally in major league pitchers.
Hypothesis: Major league pitchers (starters and relievers) experience an increase in glenohumeral external rotation and a decrease in internal rotation and total range of motion. Glenohumeral internal rotation deficit worsens over a regular playing season.
Study design: Retrospective cohort study.
Methods: In 21 major league baseball pitchers (29 individual playing seasons), glenohumeral range of motion was measured in external and internal rotation for the throwing and nonthrowing shoulders before and at the conclusion of the regular season. The total range of motion (the sum of external rotation and internal rotation) and the glenohumeral internal rotation deficit were calculated (the difference between internal rotation of the nonthrowing shoulder minus that of the throwing shoulder), and data were compared between starting and relief pitchers.
Results: The overall mean changes in external rotation (+1.5°), internal rotation (+2.7°), and total range of motion (+3.3°) were not statistically significant. However, starting pitchers showed statistically significant increases in internal rotation (+6.5°, P = 0.01) and total range of motion (+7.9°, P = 0.04), whereas relief pitchers had significant worsening of glenohumeral internal rotation deficit (+5.3°, P = 0.04).
Conclusions: The characteristics of glenohumeral range of motion in major league pitchers did not differ significantly from the beginning to the end of a season, but significant changes did occur between starting and relief pitchers.
Clinical relevance: Adaptations to the daily routines of starter and reliever pitchers may be warranted on the basis of these findings.
Keywords: baseball; glenohumeral range of motion; pitching; shoulder.