Original article
Valgus torque in youth baseball pitchers: a biomechanical study

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Abstract

The purpose of this study was to determine the biomechanical and anthropometric factors contributing to elbow valgus torque during pitching. Video data of 14 youth pitchers throwing fastballs were used to calculate shoulder and elbow kinematics and kinetics. Peak elbow valgus torque averaged 18 Nm and occurred just before maximal shoulder external rotation. The magnitude of valgus torque was most closely correlated with the thrower's weight. When subject weight and height were controlled for, maximum shoulder abduction torque and maximum shoulder internal rotation torque were most strongly associated with elbow valgus torque, accounting for 85% of its variance (P < .001). When only kinematic variables were considered, maximum shoulder external rotation accounted for 33% of the variance in valgus torque. Given that the biomechanical variables correlated with peak valgus torque are not easily modifiable, limiting the number of innings pitched is likely the best way to reduce elbow injury in youth pitchers.

Section snippets

Data collection

Two high-speed video cameras were used to videotape fourteen 12-year-old youth baseball pitchers at 120 frames per second. All subjects were male, right hand–dominant baseball pitchers. The Regis University Institutional Review Board (Denver, CO) approved the study protocol. The procedures were explained to the subjects and their parents, who provided informed consent. The subjects pitched from an indoor pitching mound to a catcher situated at a regulation distance (14 m) from the mound. The

Results

The mean age for the 14 subjects was 12.1 ± 0.4 years, with a range of 11.4 to 12.6 years. The mean subject height was 1.54 m (range, 1.42-1.68 m), and the mean mass was 44.3 kg (range, 36.6-67.1 kg). The mean pitch velocity was 48.2 mph, or 21.6 m/s. Shoulder abduction remained near 90° through the pitching cycle, averaging 95° ± 7° at SFC, 92° ± 8° at MER, and 94° ± 8° at REL. Shoulder horizontal flexion-extension (or horizontal abduction-adduction) progressed from a position of extension to

Discussion

The biomechanics of the upper extremity while throwing have been well documented in adults.13, 15, 19, 21, 33, 36, 38 Surprisingly, there are considerably fewer data describing the biomechanics of youth pitchers, even though there are a large number active in sports and they have a significant incidence of injury, especially at the elbow.31, 40 A significant portion of these elbow injuries have been attributed to elbow valgus torque generated during throwing.31 This study used established

Acknowledgements

We would like to thank to Michael Keirns, Mike Decker, Tim Cook, Jon Kedrowski, and the Regis University Physical Therapy students for help with data collection and analysis, as well as Elif Patterson for her help with the artwork.

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    Dr Sabick is currently affiliated with the Biomechanics Research Laboratory, Department of Mechanical Engineering, Boise State University, Boise, ID, USA

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