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Excerpt
During the delivery phase of pitching, maximum external rotation at the shoulder joint ranges from 150 to 180 deg. Elbow extension speeds as high as 3000 deg/second have been observed. The forces and torques producing these movements at the shoulder and elbow place tremendous tension on the soft tissues of the medial elbow and tend to compress the lateral side of the elbow. Therefore, the purpose of this study was to further quantify elbow loads in professional pitchers and to investigate the relationships between elbow stress and pitching mechanics. High-speed (120 Hz) video data were collected on 40 Major League Baseball pitchers during Spring Training in the 1998 Cactus League. Twenty body landmarks and the ball were digitized, frame by frame, throughout the pitching motion from two camera views for each athlete. Data from the two cameras were then synchronized in time and mathematically combined to produce a three-dimensional representation of the pitch for one fast ball for each pitcher. Average ball speed for the 40 pitchers was 85.3 ± 6.2 mph. During the delivery phase, maximum external rotation at the shoulder joint averaged 183.7 ± 13.4 deg. Internal rotation velocities in excess of 8500 deg/sec were documented. An average peak varus torque of 121.6 ± 15.5 Nm was found near the instant of maximum external rotation. A compressive force (807.7 ± 161.9 N) occurred at the elbow joint near the instant of ball release. Regression equations relating the kinematic parameters of pitching mechanics to elbow varus torque were obtained. Knowledge of joint ranges of motion, angular velocities and joint reaction forces can provide a scientific basis for improved preventive and rehabilitative protocols for baseball pitchers, especially at an early age when improper mechanics are more easily addressed.
