Though contralateral trunk tilt has been studied, the phenomena of excessive ipsilateral trunk tilt, which is typically noticed during the early stages of a pitch, has yet to be investigated as a possible connection with baseball pitchers’ throwing arm kinematics. This study aimed to determine kinetic and kinematic characteristics associated with excessive ipsilateral/contralateral trunk tilt in high school and professional pitchers. While pitching, 3D-motion capture (480 Hz) was used by researchers to evaluate professional and high school pitchers. Excessive ipsilateral tilt at foot contact (FC), neutral, or excessive contralateral tilt at ball release (BR) was assigned by investigators to pitchers (BR). Post-hoc regression analysis was used to evaluate trunk and shoulder kinematics and throwing arm kinetics between subgroups.
When compared to high schools (n=59), professional pitchers (n=287) had considerably larger ipsilateral trunk tilt at FC (p<0.001). When compared to the ipsilateral trunk tilt cohort, high school pitchers with excessive contralateral trunk tilt had significantly higher shoulder superior force (27.0±7.4 vs. 17.6±5.1 % BW respectively, p<0.001) and shoulder anterior force(39.6±8.2 vs. 35.7±5.4 % BW respectively, p<0.001), while having comparable ball velocity (30.2±3.2 vs. 30.4±2.1m/s, p=0.633). Ball velocity increased by 0.2m/s(B:0.02:0.07 SE: 0.005 p=0.010) for every 10° increase in ipsilateral trunk tilt at FC for professionals, while elbow varus torque(EVT) decreased by 0.1 % BWxHeight (B:-0.01:-0.08 SE:0.002 p<0.001) and shoulder internal rotation torque (SIRT) decreased by 0.1 % BWxHeight (B:-0.01:-0.07 SE: When comparing pitchers with excessive ipsilateral trunk tilt at FC to pitchers with excessive contralateral trunk tilt at BR, throwing arm kinetics (high school: anterior shoulder force, superior shoulder force; professional: SIRT, EVT) were consistently lower (high school: anterior shoulder force, superior shoulder force; professional: SIRT, EVT). Furthermore, when compared to high school pitchers, professional pitchers appear to engage in significantly more ipsilateral trunk tilt early in the pitch, which could be a kinetically advantageous method used by pitchers at higher levels to maintain adequate ball velocity while minimizing throwing arm kinetics.