Throwing Arm Dominance in Collegiate Baseball Pitching

Abstract

Background: Left-handed individuals make up about 10% of the general population, yet left-handers comprise approximately 30% of the pitching staffs in Major League and Division I college baseball. Despite speculation regarding differences between right- and left-handed pitchers, distinction between right- and left-handed pitching mechanics has not been documented in the literature at any level of play. Hypothesis: Left-hand–dominant pitchers display similar pitching mechanics and upper extremity joint loads when compared to their right-hand–dominant counterparts. Study Design: Controlled laboratory study. Methods: Three-dimensional, high-speed (240-Hz) video data were collected on fastballs from 84 collegiate baseball pitchers. Kinematic parameters related to pitching mechanics and resultant kinetics on the throwing shoulder and elbow were calculated. The 28 left-handed pitchers in the database were matched with 28 right-handed pitchers for age, height, mass, and ball velocity, and paired t tests were used to compare the kinematic and kinetic parameters. Results: Six parameters were found to have statistically significant differences between left- and right-handed pitchers. Passive nonthrowing shoulder external rotation (right, 113° ± 9°; left, 124° ± 8°), elbow flexion at stride-foot contact (right, 79° ± 16°; left, 94° ± 20°), and shoulder abduction during acceleration (right, 72° ± 11°; left, 105° ± 8°) were greater in left-handed pitchers than right-handed pitchers. Shoulder abduction at stride-foot contact (right, 115° ± 13°; left, 73° ± 10°), shoulder horizontal abduction at stride-foot contact (right, 25° ± 12°; left, 15° ± 12°), and peak horizontal adduction angular velocity (right, 707 ± 185 deg/s; left, 551 ± 160 deg/s) were less for the left-handed pitchers. Conclusion: Biomechanical differences between left- and right-handed pitchers have been demonstrated in a collegiate population. Clinical Relevance: The results of the current study indicate that left-handed pitchers may be at increased risk for certain shoulder injuries compared with their right-handed counterparts. Information has been provided for athletes, coaches, and sports medicine providers to further improve preventive and rehabilitative protocols for college pitchers. The results of the study also suggest that different normative data sets may need to be developed for left- and right-handed pitchers, independently of one another.