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  • Author: James R. Andrews x
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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.

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Yungchien Chu, Glenn S. Fleisig, Kathy J. Simpson and James R. Andrews

The purpose of the current study was to identify the biomechanical features of elite female baseball pitching. Kinematics and kinetics of eleven elite female baseball pitchers were reported and compared with eleven elite male pitchers. Results suggested that females share many similarities with males in pitching kinematics, with a few significant differences. Specifically, at the instant of stride foot contact, a female pitcher had a shorter and more open stride and less separation between pelvis orientation and upper torso orientation. From foot contact to ball release, a female pitcher produced lower peak angular velocity for throwing elbow extension and stride knee extension. Ball velocity was lower for the female. Foot contact to ball release took more time for a female pitcher. Maximal proximal forces at the shoulder and elbow joints were less for a female pitcher.

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Kevin E. Wilk, Naiquan Zheng, Glenn S. Fleisig, James R. Andrews and William G. Clancy

Closed kinetic chain exercise has become popular in rehabilitation of the ACL patient. While many clinicians agree on the benefits of closed kinetic chain exercise, there is great discrepancy as to which exercises fit this category. This discrepancy stems from the fact that the kinetic chain concept was originally developed using mechanical engineering concepts and not human kinesiology. In this paper, the kinetic chain concept is redefined in a continuum of lower extremity exercises from closed kinetic chain to open kinetic chain. The placement of an exercise in this continuum is based upon joint kinematics, quadriceps and hamstring muscle activity, cruciate ligament stress, and joint weight-bearing load. An understanding of these factors can help the clinician design a comprehensive and effective rehabilitation program for the ACL patient.

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Kevin E. Wilk, James R. Andrews, William G. Clancy Jr., Heber C. Crockett and James W. O'Mara Jr.

Treatment of posterior cruciate ligament (PCL) injuries has changed considerably in recent years. This article discusses current rehabilitation for PCL disruptions in athletes. The treatment of PCL injuries varies somewhat based on the chronicity (acute vs. chronic) of injury and associated pathologies. The authors provide their treatment algorithm for the acute and chronic PCL-injured-knee patient. Nonoperative rehabilitation is discussed with a focus on immediate motion, quadriceps muscle strengthening, and functional rehabilitation. A discussion of the biomechanics of exercise is provided, with a focus on tibiofemoral shear forces and PCL strains. Surgical treatment is also discussed, with the current surgical approach being either the two-tunnel or the one-tunnel patellar tendon autograft procedure. The rehabilitation program after surgery is based on the healing constraints, surgical technique, biomechanics of the PCL during functional activities, and exercise. With the new changes in surgical technique and in the rehabilitation process, the authors believe that the outcome after PCL reconstruction will be enhanced.

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Michael M. Reinold, Glenn S. Fleisig, James R. Andrews, Kevin E. Wilk and Gene G. Jameson

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Gretchen D. Oliver, Jessica K. Washington, Sarah S. Gascon, Hillary A. Plummer, Rafael F. Escamilla and James R. Andrews

Context: Hip abductor musculature contributes to the stability of the pelvis, which is needed for efficient energy transfer from the lower-extremity to the upper-extremity during overhead throwing. Objective: The purpose of this study was to examine the effects of a bilateral hip abduction fatigue protocol on overhead-throwing kinematics and passive hip range of motion. Design: Prospective cohort study. Setting: Controlled laboratory setting. Participants: A convenience sample of 19 collegiate female softball players (20.6 [1.9] y; 169.3 [9.7] cm; 73.2 [11.2] kg). Main Outcome Measures: Repeated hip abduction to fatigue was performed on an isokinetic dynamometer for 3 consecutive days. Trunk and shoulder kinematics during throwing and hip internal and external rotation range of motion were analyzed prior to fatigue on day 1 (prefatigue) and following fatigue on day 3 (postfatigue). Results: Repeated-measures analysis of variances revealed no statistically significant differences in trunk and shoulder kinematics prefatigue and postfatigue. A statistically significant time × side × direction interaction (F 2,36 = 5.462, P = .02, ηp2=.233) was observed in hip passive range of motion. A decrease in throwing-side hip internal rotation prefatigue to postfatigue (mean difference = −2.284; 95% confidence interval, −4.302 to −0.266; P = .03) was observed. Conclusions: The hip abductor fatigue protocol used in this study did not significantly alter trunk and upper-extremity throwing kinematics. The lack of changes may indicate that fatigue of the hip abductors does not contribute to trunk and shoulder kinematics during throwing or the protocol may not have been sport-specific enough to alter kinematics.

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Rafael F. Escamilla, Glenn S. Fleisig, Coop DeRenne, Marcus K. Taylor, Claude T. Moorman III, Rodney Imamura, Edward Barakatt and James R. Andrews

A motion system collected 120-Hz data from 14 baseball adult hitters using normal and choke-up bat grips. Six swings were digitized for each hitter, and temporal and kinematic parameters were calculated. Compared with a normal grip, the choke-up grip resulted in 1) less time during stride phase and swing; 2) the upper torso more opened at lead foot contact; 3) the pelvis more closed and less bat linear velocity at bat-ball contact; 4) less range of motion of the upper torso and pelvis during swing; 5) greater elbow flexion at lead foot contact; and 6) greater peak right elbow extension angular velocity. The decreased time during the stride phase when using a choke-up grip implies that hitters quicken their stride when they choke up. Less swing time duration and less upper torso and pelvis rotation range of motion using the choke-up grip supports the belief of many coaches and players that using a choke-up grip results in a “quicker” swing. However, the belief that using a choke-up grip leads to a faster moving bat was not supported by the results of this study.

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Rafael F. Escamilla, Glenn S. Fleisig, Coop DeRenne, Marcus K. Taylor, Claude T. Moorman III, Rodney Imamura, Edward Barakatt and James R. Andrews

We propose that learning proper hitting kinematics should be encouraged at a young age during youth baseball because this may help reinforce proper hitting kinematics as a player progresses to higher levels of baseball in their adult years. To enhance our understanding between youth and adult baseball hitting, kinematic and temporal analyses of baseball hitting were evaluated with a high-speed motion analysis system between 12 skilled youth and 12 skilled adult baseball players. There were only a small number of temporal differences between youth and adult hitters, with adult hitters taking significantly greater time than youth hitters during the stride phase and during the swing. Compared with youth hitters, adult hitters a) had significantly greater (p < .01) lead knee flexion when the hands started to move forward; b) flexed the lead knee over a greater range of motion during the transition phase (31° versus 13°); c) extended the lead knee over a greater range of motion during the bat acceleration phase (59° versus 32°); d) maintained a more open pelvis position at lead foot off ground; and e) maintained a more open upper torso position when the hands started to move forward and a more closed upper torso position at bat-ball contact. Moreover, adult hitters had greater peak upper torso angular velocity (857°/s versus 717°/s), peak left elbow extension angular velocity (752°/s versus 598°/s), peak left knee extension angular velocity (386°/s versus 303°/s), and bat linear velocity at bat-ball contact (30 m/s versus 25 m/s). The numerous differences in kinematic and temporal parameters between youth and adult hitters suggest that hitting mechanics are different between these two groups.