Jeffrey T. Wight1,2, Brittany Dowling3, Christopher J. Rodriguez1, George G.A. Pujalte, FACSM2. 1-Jacksonville University, -Jacksonville, FL. 2Mayo Clinic, -Jacksonville, FL. 3Midwest Orthopaedics at Rush, Oak Brook, IL.

BACKGROUND: Elite baseball pitchers rapidly rotate the upper-torso (UT) during the arm-cocking phase of the pitch. By the end of this phase, the UT is “facing the catcher” (approximately 95°). Then, the arm-acceleration phase begins. Interestingly, UT axial rotation becomes highly variable during this phase. Some pitchers cease UT rotation while others continue to rotate the UT another 20°. PURPOSE: Determine if UT axial rotation style (during the arm-acceleration phase of the pitch) impacts overall pitching biomechanics. METHODS: 285 professional pitchers (25.8±6.0 yrs) were evaluated using 8-camera motion capture system (Motion Analysis Corporation, Santa Rosa CA) at 480 Hz. Each pitcher threw approximately 10 fastball pitches and the fastest strike was analyzed. Two groups were formed (N=45 in each group) based on the amount of UT rotation completed during the arm acceleration phase (19.2° ±2.5° vs. 4.6°±2.0°). Independent t-tests were used to test for significant differences in throwing velocity, overall torso kinematics, and critical throwing arm kinetics. RESULTS: There were no significant differences (p=0.10) in throwing velocity between the rotators (39.9±1.8m/s) and non-rotators (39.3±1.6m/s). The non-rotators generated significantly more (p<0.01) torso lateral flexion at ball release (27.0±11.0° vs. 11.3±10.0°) and had a significantly higher (p<0.01) peak torso flexion velocity (467.0±209.5°/s vs. 356.5±146.6°/s). The rotators had a more “open” pelvis at the beginning of the arm-acceleration phase (103.3±10.4° vs. 95.7±18.3°) and a significantly higher (p<0.01) peak pelvis rotational velocity (726.4±94.9°/s vs. 638.0±106.1°/s). Kinetic analysis revealed that rotators had a significantly higher (p<0.01) peak shoulder distraction force (1156.3±195.7N vs. 1046.0±171.3N), but there were no differences (p=0.77) in peak elbow valgus torque (87.6±16.6N·m vs. 88.9 ±16.0N·m ). CONCLUSION: Pitchers with limited UT axial rotation appear to rely more on torso flexion and torso lateral flexion strategies. Future studies should attempt to understand why the axial rotators had a higher peak shoulder distraction force.

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