Baseball coaches train pitchers to keep their shoulder abduction at 90º during delivery, because this angle is believed to maximize ball speed and reduce the stress on the throwing arm. In fact, however, the shoulder abduction angle for some pitchers, including professional pitchers, deviates from 90º. There likely are reasons for such deviation. The purposes of this study, therefore, were to investigate the effects of shoulder abduction angle on ball velocity and on the injury-related joint kinetic variable, and to determine why the shoulder abduction angle varies among pitchers. Eleven professional pitchers were videotaped with two high-speed cameras. The resulting kinematic data were used to simulate several pitching motions by varying the shoulder abduction angle from the actual angle. Maximum wrist velocity was used as a reasonable approximation of ball velocity. Elbow varus torque was used as a kinetic variable. The square torque for the throwing arm and torque change for the throwing arm were used to investigate the cause of the variation. It was found that the shoulder abduction angle of 90º did not always maximize wrist velocity nor minimize elbow varus torque. The actual shoulder abduction angle for each pitcher was highly consistent with the angle that minimized both square torque and torque change. The results suggested that the proficient throwers in this study moved their pitching arm so as to minimize mechanical cost while at the same time optimizing performance.
Tomoyuki Matsuo, Tsuyoshi Matsumoto, Yoshiyuki Mochizuki, Yoshihiro Takada, and Kenji Saito
Tomoyuki Matsuo, Glenn S. Fleisig, Naiquan Zheng, and James R. Andrews
Elbow varus torque is a primary factor in the risk of elbow injury during pitching. To examine the effects of shoulder abduction and lateral trunk tilt angles on elbow varus torque, we conducted simulation and regression analyses on 33 college baseball pitchers. Motion data were used for computer simulations in which two angles— shoulder abduction and lateral trunk tilt—were systematically altered. Forty-two simulated motions were generated for each pitcher, and the peak elbow varus torque for each simulated motion was calculated. A two-way analysis of variance was performed to analyze the effects of shoulder abduction and trunk tilt on elbow varus torque. Regression analyses of a simple regression model, second-order regression model, and multiple regression model were also performed. Although regression analyses did not show any significant relationship, computer simulation indicated that the peak elbow varus torque was affected by both angles, and the interaction of those angles was also significant. As trunk tilt to the contralateral side increased, the shoulder abduction angle producing the minimum peak elbow varus torque decreased. It is suggested that shoulder abduction and lateral trunk tilt may be only two of several determinants of peak elbow varus torque.
Tomoyuki Matsuo, Rafael F. Escamilla, Glenn S. Fleisig, Steven W. Barrentine, and James R. Andrews
This study investigated differences in kinematic and temporal parameters between two velocity groups of baseball pitchers. Data were collected from 127 healthy college and professional baseball pitchers. Those who threw faster than 1 SD above the sample mean (>38.0 m/s) were assigned to the high velocity group (n = 29), and those who threw slower than 1 SD below the sample mean (<34.2 m/s) were assigned to the low velocity group (n = 23). Twelve kinematic parameters and 9 temporal parameters were measured and analyzed. The pattern of lead knee movement was also investigated. Maximum shoulder external rotation, forward trunk tilt at the instant of ball release, and lead knee extension angular velocity at the instant of ball release were significantly greater in the high velocity group. Maximum lead knee flexion angular velocity was significantly greater in the low velocity group. Seventy percent of the high velocity group showed knee extension during the approach to ball release, whereas the low velocity group showed a variety of knee movement patterns involving less knee extension and more knee flexion. The greater shoulder external rotation in the high velocity group produced an increased range of motion during the acceleration phase.
Steven W. Barrentine, Tomoyuki Matsuo, Rafael F. Escamilla, Glenn S. Fleisig, and James R. Andrews
Previous researchers studying baseball pitching have compared kinematic and kinetic parameters among different types of pitches, focusing on the trunk, shoulder, and elbow. The lack of data on the wrist and forearm limits the understanding of clinicians, coaches, and researchers regarding the mechanics of baseball pitching and the differences among types of pitches. The purpose of this study was to expand existing knowledge of baseball pitching by quantifying and comparing kinematic data of the wrist and forearm for the fastball (FA), curveball (CU) and change-up (CH) pitches. Kinematic and temporal parameters were determined from 8 collegiate pitchers recorded with a four-camera system (200 Hz). Although significant differences were observed for all pitch comparisons, the least number of differences occurred between the FA and CH. During arm cocking, peak wrist extension for the FA and CH pitches was greater than for the CU, while forearm supination was greater for the CU. In contrast to the current study, previous comparisons of kinematic data for trunk, shoulder, and elbow revealed similarities between the FA and CU pitches and differences between the FA and CH pitches. Kinematic differences among pitches depend on the segment of the body studied.
Glenn S. Fleisig, Rafael F. Escamilla, James R. Andrews, Tomoyuki Matsuo, Yvonne Satterwhite, and Steve W. Barrentine
Kinematic and kinetic aspects of baseball pitching and football passing were compared. Twenty-six high school and collegiate pitchers and 26 high school and collegiate quarterbacks were analyzed using three-dimensional high-speed motion analysis. Although maximum shoulder external rotation occurred earlier for quarterbacks, maximum angular velocity of pelvis rotation, upper torso rotation, elbow extension, and shoulder internal rotation occurred earlier and achieved greater magnitude for pitchers. Quarterbacks had shorter strides and stood more erect at ball release. During arm cocking, quarterbacks demonstrated greater elbow flexion and shoulder horizontal adduction. To decelerate the arm, pitchers generated greater compressive force at the elbow and greater compressive force and adduction torque at the shoulder. These results may help explain differences in performance and injury rates between the two sports.