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Inverse Dynamics Analysis Of Youth Pitching Arm Kinetics Using Body Composition Imaging, Jay A. Sterner, Scott K. Reaves, Arnel L. Aguinaldo, Scott Hazelwood, Stephen M. Klisch

Biomedical Engineering

This study’s objectives were to: (1) assess whether dual energy X-ray absorptiometry (DXA)-mass inverse dynamics (ID) alters predictions of youth pitching arm kinetics and (2) investigate correlations between kinetics and body composition. Eighteen 10- to 11-year-olds pitched 10 fastballs. DXA scans were conducted to obtain participant-specific upper arm, forearm, and hand masses. Pitching arm segment masses and kinetics calculated with scaled and DXA masses were compared with paired t-tests and correlations were investigated with linear regression. Hand (p < 0.001) and upper arm (p < 0.001) DXA masses were greater, while forearm (p < 0.001) DXA masses were lesser, than their scaled masses. Shoulder compressive force (p < 0.001), internal rotation torque (p < 0.001), and horizontal adduction torque (p = 0.002) increased when using DXA masses. Shoulder compressive force correlated with body mass (p < 0.001) and body mass index (BMI; p = 0.002) and elbow varus torque correlated with body mass (p < 0.05). The main conclusions were that (1) using participant-specific mass ratios leads to different predictions of injury-related pitching arm kinetics and, thus, may improve our understanding of injury risk factors; and (2) pitching arm kinetics were correlated with body composition measures and a relatively high total body mass and/or BMI may increase shoulder and/or elbow injury risk.