Youth Pitching Biomechanics

 

Over the past several years, we have conducted several studies on youth pitching biomechanics with the aim of improving evidence-based injury prevention guidelines for youth baseball pitchers. As shown in the figure above, (left) markers are placed on the pitchers and cameras record the motion of the markers and computer software calculates (middle) marker trajectories and (right) skeletal motion. Post-processing the data with inverse dynamic analyses, which uses the principles of rigid body dynamics, then allows us to calculate the loads (forces and torques) on the shoulder and elbow joints of youth pitchers.

Currently, we are extending this work to include softball pitchers, who are an at-risk and understudied population for pitching injuries, and older baseball pitchers.

Current and past students that have worked on these projects include Michael Roth, Erin Malone, Kendall Gentzen, Sydney Donaldson, Carlos Soto, Karthik Padmanabhan, Christina Fong, Ryan Sax, Dalton Jennings, Jay Sterner, Eshan Dandekar, and Jim Darke.

Journal Papers

• Jennings DJ, Reaves SK, Sklar J, Brown C, McPhee J, Hazelwood SJ, Klisch SM. Baseball pitching arm 3-D inertial parameter calculations from body composition imaging and a novel overweight measure for youth pitching arm kinetics. ASME Journal of Biomechanical Engineering, 144(44):041007, Apr 2022. https://doi.org/10.1115/1.4052890
• Sterner JA, Reaves SK, Aguinaldo AL, Hazelwood SJ, Klisch SM. Inverse dynamics analysis of youth pitching arm kinetics using body composition imaging. Sports Biomechanics, March, 2020. https://doi.org/10.1080/14763141.2020.1715470
• Darke JD, Dandekar EM, Aguinaldo AL, Hazelwood SJ, Klisch SM. Effects of game pitch count and body mass index on pitching biomechanics in 9-10 year old baseball athletes. Orthopaedic Journal of Sports Medicine, 6(4), April 2018. http://journals.sagepub.com/doi/full/10.1177/2325967118765655

The abstracts for several journal papers are presented below.

3-D inertial parameter calculations from body composition imaging and overweight-related indices 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 often associated with SMI than BMI. Results suggest that using participant-specific BSIPs and pitching arm SMIs may improve evidence-based injury prevention guidelines for youth pitchers. Published as a journal paper (https://doi.org/10.1115/1.4052890). 

Inverse dynamics analysis of youth pitching arm kinetics using body composition imaging.

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. Published as a journal paper (https://doi.org/10.1080/14763141.2020.1715470). 

Effects of game pitch count and body mass index on pitching biomechanics in 9- to 10-year-old baseball athletes.

We hypothesized that during a simulated game with 9-10 year olds, (1) participants will experience biomechanical signs of fatigue and (2) shoulder and elbow kinetics will correlate to body mass index (BMI). Thirteen 9-10 year old youth baseball players pitched a simulated game (75 pitches). Range of motion and muscular output tests were conducted before and after the simulated game to quantify fatigue. Kinematic parameters at foot contact, maximum external rotation, and maximum internal rotation velocity (MIRV), and maximum shoulder and elbow kinetics between foot contact and MIRV, were compared at pitches 1-5, 34-38, and 71-75. Multivariate analyses of variance were used to test the first hypothesis, and linear regressions were used to test the second hypothesis. MIRV (p=0.007) increased from pitches 1-5 to 71-75 and head flexion (p=0.022) at MIRV decreased from pitches 1-5 to 34-38. Maximum shoulder horizontal adduction (p=0.031), external rotation (p=0.023), and internal rotation (p=0.021) torques increased from pitches 34-38 to 71-75. Shoulder compression force (p=0.011) increased from pitches 1-5 to 71-75. Correlations of joint torque/force with BMI were found at every pitch period; e.g., shoulder internal rotation (R²=0.93, p<0.001) and elbow varus (R²=0.57, p=0.003) torques at pitches 1-5. Several results differed from previous studies with adult pitchers: (1) pitch speed remained steady, (2) shoulder MIRV increased, and (3) shoulder kinetics increased during a simulated game. The strong correlations between joint kinetics and BMI reinforce previous results that select body composition measures may be correlated with pitching arm joint kinetics for youth baseball pitchers. The results improve our understanding of pitching biomechanics for 9-10 year old baseball pitchers and may be used in future studies to improve evidence-based injury prevention guidelines. Published as a journal paper (http://journals.sagepub.com/doi/full/10.1177/2325967118765655).