Implications of Planar Postural Metrics and Kinematics on Pitch Velocity and Kinetics in Baseball Pitchers

• Main Author: Semkewyc, Courtney Erin
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2022
• Subjects: Biomechanics; Biomedical engineering
• ISBN: 9798790633188

Two key metrics to a baseball pitcher’s success and longevity are their pitch velocity and injury risk. Pitchers are susceptible to injury due to high velocities and stresses generated during the pitching motion. These injuries commonly occur at the shoulder or elbow and are typically a result of high torques experienced at the segment joint. Some pitchers reduce their joint torque by having a more efficient pitching motion in which their mechanics allow for a high pitch velocity and decreased torque. As a result, it is important to determine metrics that decrease torque, while maintaining pitch velocity. There is a need to expand the knowledge of these postural and kinematic metrics, and to analyze anatomical factors that may influence them. The mechanics of 62 pitchers were examined through motion capture, and an array of metrics in all three anatomical planes was analyzed for correlations to pitch velocity and maximum torque in the form of elbow varus torque, shoulder internal rotation torque, and shoulder horizontal abduction torque. The correlated metrics included kinematic angular velocities and postural metrics at three pitching checkpoints of foot plant, maximum external rotation (MER), and release. In terms of postural metrics knee flexion at MER (r = –0.453) and shoulder external rotation at MER (r = 0.465) both had moderate correlations to pitch velocity, but no implications for injury. Alternatively, pelvis forward tilt, trunk forward tilt, and shoulder horizontal abduction were determined to be tradeoff metrics in which an increase in angle resulted in both an increase in pitch velocity and torque. These postural metrics had the highest correlations to torque but were only weak correlations. Kinematic parameters had moderate to strong correlations for both pitch velocity and torque. There was no crossover between the correlated metrics with pitch velocity having correlations to the maximum angular velocities of the sagittal pelvis, transverse torso, sagittal elbow, and transverse shoulder horizontal adduction. All three examined torques had correlations to the maximum hand angular velocity in each of the three planes of motion. The highest correlation was maximum hand sagittal angular velocity to maximum elbow varus torque (r = 0.745). Anatomical factors of height, weight, age, segment lengths, arm slot, and mobility were examined for their influence on the postural and kinematic metrics. Weight was correlated to pitch velocity and height to arm slot. In terms of arm slot, it was discovered that pitchers with a more vertical arm slot use more sagittal plane movements to gain velocity, while more horizontal arm slot pitchers use transverse plane movements. Mobility assessments provided significant differences between pitchers with limited mobility and pitchers with adequate mobility. The pitchers with limited mobility had more significant decreases in metrics correlated to pitch velocity and increases in upper extremity kinetics. It is important for pitchers to maintain their mobility to combat anatomical adaptations, maintain pitch velocity, and mitigate their risk of injury. Pitching coaches can use this information to develop better individualized training programs to help pitchers improve performance while decreasing their risk of injury.