Glenohumeral Rotational Motion and Strength and Baseball Pitching Biomechanics

Context: Addressing loss of shoulder range of motion and rotator cuff weakness in injury-prevention programs might be an effective strategy for preventing throwing arm injuries in baseball pitchers. However, the influence of these clinical measures on pitching biomechanics is unclear. Objective: To evaluate the relationships among clinical measures of shoulder rotational motion and strength and 3-dimensional pitching biomechanics and to evaluate the presence of coupling between the shoulder and the elbow during pitching to provide insight into the influence of clinical shoulder characteristics on elbow biomechanics. Design: Cross-sectional study. Setting: Biomechanics laboratory. Patients or Other Participants: A total of 27 uninjured male high school baseball pitchers (age = 16 +/- 1.1 years, height = 183 +/- 7 cm, mass = 83 +/- 12 kg). Main Outcome Measure(s): Clinical measures included shoulder internal- and external-rotation range of motion and peak isometric internal- and external-rotator strength. Three-dimensional upper extremity biomechanics were assessed as participants threw from an indoor pitching mound to a target at regulation distance. Linear regressions were used to assess the influence of clinical measures on the peak shoulder internal and external rotation moments and the peak elbow-adduction moment. Results: We found a positive relationship between clinically measured internal-rotator strength and shoulder external-rotation moment (R-2 = 0.181, P = .04) during pitching. We also noted an inverse relationship between clinically measured external-rotation motion and the elbow-adduction moment (R-2 = 0.160, P = .04) and shoulder internal-rotation moment (R-2 = 0.250, P = .008) during pitching. We found a positive relationship between peak shoulder internal-rotation moment and the peak elbow-adduction moment (R-2 = 0.815, P < .001) during pitching. Conclusions: This study provides insight into the effects of shoulder strength and motion on pitching biomechanics and how these clinical measures might contribute to throwing arm injuries in the baseball pitcher. A relationship also was identified between peak shoulder and elbow moments in the throwing arm during pitching, providing biomechanical support for addressing clinical shoulder characteristics as a potential strategy for preventing elbow injury.