A profile of glenohumeral internal and external rotation motion in the uninjured high school baseball pitcher, part I: Motion

Context: The magnitude of motion that is normal for the throwing shoulder in uninjured baseball pitchers has not been established. Chronologic factors contributing to adaptations in motion present in the thrower's shoulder also have not been established. Objectives: To develop a normative profile of glenohumeral rotation motion in uninjured high school baseball pitchers and to evaluate the effect of chronologic characteristics on the development of adaptations in shoulder rotation motion. Design: Cohort study. Setting: Baseball playing field. Patients or Other Participants: A total of 210 uninjured male high school baseball pitchers (age = 16 ± 1.1 years, height = 1.8 ± 0.1 m, mass = 77.5 ± 11.2 kg, pitching experience = 6 ± 2.3 years). Intervention(s): Using standard goniometric techniques, we measured passive rotational glenohumeral range of motion bilaterally with participants in the supine position. Main Outcome Measure(s): Paired t tests were performed to identify differences in motion between limbs for the group. Analysis of variance and post hoc Tukey tests were conducted to identify differences in motion by age. Linear regressions were performed to determine the influence of chronologic factors on limb motion. Results: Rotation motion characteristics for the population were established. We found no difference between sides for external rotation (ER) at 0° of abduction (t₂₀₉ = 0.658, P = .51), but we found side-to-side differences in ER (t₂₀₉ = -13.012, P < .001) and internal rotation (t₂₀₉ = 15.304, P < .001) at 90° of abduction. Age at the time of testing was a significant negative predictor of ER motion for the dominant shoulder (R2 = 0.019, P = .049) because less ER motion occurred at the dominant shoulder with advancing age. We found no differences in rotation motion in the dominant shoulder across ages (F_4.205 range, 0.451-1.730, P > .05). Conclusions: This range-of-motion profile might be used to assist with the interpretation of normal and atypical shoulder rotation motion in this population. Chronologic characteristics of athletes had no influence on range-of-motion adaptations in the thrower's shoulder.