Baseball Pitching Arm 3-D Inertial Parameter Calculations from Body Composition Imaging and a Novel Overweight Measure for Youth Pitching Arm Kinetics

Many baseball pitching studies have used inverse dynamics to assess throwing arm kinetics as high and repetitive kinetics are thought to be linked to pitching injuries. However, prior studies have not used participant-specific body segment inertial parameters (BSIPs) which are thought to improve analysis of high-acceleration motions and overweight participants. This study's objectives were to 1) calculate participant-specific BSIPs using DXA measures, 2) compare inverse dynamic calculations of kinetics determined by DXA-calculated BSIPs (full DXA-driven inverse dynamics) against kinetics using the standard inverse dynamics approach with scaled BSIPs (scaled inverse dynamics), and 3) examine associations between full DXA-driven kinetics and overweight indices: body mass index (BMI) and segment mass index (SMI). Eighteen participants (10-11 years old) threw 10 fastballs that were recorded for motion analysis. DXA scans were used to calculate participant-specific BSIPs (mass, center of mass, radii of gyration) for each pitching arm segment (upper arm, forearm, hand), BMI, and SMI. The hypotheses were addressed with t-tests and linear regression analyses. The major results were that 1) DXA-calculated BSIPs differed from scaled BSIPs for each pitching arm segment, 2) calculations for shoulder, but not elbow, kinetics differed between the full DXA-driven and scaled inverse dynamics analyses, and 3) full DXA-driven inverse dynamics calculations for shoulder kinetics were more strongly associated with SMI than with BMI. Results suggest that using participant-specific BSIPs and pitching arm SMIs may improve evidence-based injury prevention guidelines for youth pitchers.