Sherry L. Werner

Relationships between Throwing Mechanics and Shoulder Distraction in Professional Baseball Pitchers

The extreme forces and torques and the high speeds and excessive ranges of motion of baseball pitching place tremendous stress on the soft tissues of the throwing shoulder. Little is known about the relationship between pitching mechanics and shoulder joint stress, especially in professional athletes. The purpose of this study was to quantify joint loads and kinematic parameters of pitching mechanics at the major league level and to study their relationships. Three-dimensional, high-speed video data were collected on 40 professional pitchers during the 1998 Cactus League spring training. A clinically significant distraction force was calculated at the shoulder joint, which reached an average peak value of 947±162 N (108%±16% body weight). Descriptive statistics and a multiple linear regression analysis were used to relate shoulder distraction to kinematic and kinetic parameters of pitching mechanics. This study was undertaken not only to investigate the peak forces and torques on the shoulder, but also to identify potential areas of intervention that might prevent throwing injuries. 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.

The Effects of Extended Play on Professional Baseball Pitchers

The purpose of this study was to investigate kinematic and kinetic changes as a result of extended play in baseball pitching. Seven major league baseball pitchers were videotaped with high-speed (120 Hz) cameras during multiple innings of the same game. For each athlete, two fastballs (one thrown during the initial inning of play and one from the final inning) were chosen for analysis. Twenty-one physical landmarks were manually digitized from the video data. Kinematic and kinetic parameters were subsequently calculated relative to four phases of the pitching motion: windup, cocking, acceleration, and follow-through. Paired t-tests revealed that seven parameters changed significantly between early and late innings. These included decreases in maximum external rotation of the shoulder, knee angle at ball release, ball velocity, maximum distraction force at both the shoulder and elbow, and horizontal adduction torque at both release and its maximum value. Ultimately, a decline in performance was evident by a 2 m/s (5 mph) drop in ball speed. It is unclear whether the kinematic and kinetic changes occurred because of fatigue or if protective mechanisms were adopted.

Relationships between ball velocity and throwing mechanics in collegiate baseball pitchers

Although ball speed is considered a measure of success in baseball pitching, little is known about the relationship between ball velocity and pitching mechanics. Investigation of this relationship has been limited, and the studies carried out have varied in methodology. Three-dimensional, high-speed (240 Hz) video data were collected on fastballs from 54 collegiate baseball pitchers. Kinematic parameters related to pitching mechanics and resultant kinetics on the throwing shoulder and elbow were calculated. Multiple linear regression analysis was used to relate ball velocity and pitching mechanics. Ball velocity averaged 35 m/sec (79 mph) for the 54 college pitchers. Nearly 70% of the variability in ball speed can be explained by a combination of 10 parameters related to pitching mechanics. Body mass and 9 temporal and kinematic parameters related to pitching mechanics combine to account for 68% of the variance in ball velocity for a collegiate population of athletes. These variables can be manipulated via mechanical changes and sport-specific training to affect ball velocity. The results of the study can be used to increase ball velocity while at the same time minimizing stresses on the throwing arm elbow and shoulder. Improved training programs can begin to be developed based on these data.

Kinematics and Kinetics of Elite Windmill Softball Pitching

Background A significant number of time-loss injuries to the upper extremity in elite windmill softball pitchers has been documented. The number of outings and pitches thrown in 1 week for a softball pitcher is typically far in excess of those seen in baseball pitchers. Shoulder stress in professional baseball pitching has been reported to be high and has been linked to pitching injuries. Shoulder distraction has not been studied in an elite softball pitching population. Hypothesis The stresses on the throwing shoulder of elite windmill pitchers are similar to those found for professional baseball pitchers. Study Design Descriptive laboratory study. Methods Three-dimensional, high-speed (120 Hz) video data were collected on rise balls from 24 elite softball pitchers during the 1996 Olympic Games. Kinematic parameters related to pitching mechanics and resultant kinetics on the throwing shoulder were calculated. Multiple linear regression analysis was used to relate shoulder stress and pitching mechanics. Results Shoulder distraction stress averaged 80% of body weight for the Olympic pitchers. Sixty-nine percent of the variability in shoulder distraction can be explained by a combination of 7 parameters related to pitching mechanics. Conclusion Excessive distraction stress at the throwing shoulder is similar to that found in baseball pitchers, which suggests that windmill softball pitchers are at risk for overuse injuries. Normative information regarding upper extremity kinematics and kinetics for elite softball pitchers has been established.

Biomechanics of Youth Windmill Softball Pitching

Background Limited research attention has been paid to the potentially harmful windmill softball pitch. No information is available regarding lower extremity kinetics in softball pitching. Hypothesis The stresses on the throwing arm of youth windmill pitchers are clinically significant and similar to those found for college softball pitchers. Study Design Descriptive laboratory study. Methods Three-dimensional, high-speed (240-Hz) video and stride foot force plate (1200 Hz) data were collected on fastballs from 53 youth softball pitchers. Kinematic parameters related to pitching mechanics and resultant kinetics on the throwing-arm elbow and shoulder joints were calculated. Kinetic parameters were compared to those reported for baseball pitchers. Results Elbow and shoulder joint loads were similar to those found for baseball pitchers and college softball pitchers. Shoulder distraction stress averaged 94% body weight for the youth pitchers. Stride foot ground reaction force patterns were not similar to those reported for baseball pitchers. Vertical and braking force components under the stride foot were in excess of body weight. Conclusions Excessive distraction stress and joint torques at the throwing-arm elbow and shoulder are similar to those found in baseball pitchers, which suggests that windmill softball pitchers are at risk for overuse injuries. Normative information regarding upper and lower extremity kinematics and kinetics for 12- to 19-year-old softball pitchers has been established.

Lower-extremity Ground Reaction Forces in Youth Windmill Softball Pitchers

Guido, JA, Werner, SL, and Meister, K. Lower-extremity ground reaction forces in youth windmill softball pitchers. J Strength Cond Res 23(6): 1873-1876, 2009-Ground reaction forces are important in pitching given that the only external contact a pitcher has is between the foot and the ground. Windmill softball pitchers are routinely seen clinically for injuries to the lower extremities, and lower-extremity kinetics have not been well studied. The purpose of this study was to investigate the relationships between ground reaction forces and throwing mechanics in youth windmill pitchers and to provide a scientific basis for the improvement of preventive and rehabilitative protocols. Fifty-three youth softball pitchers were tested in an indoor facility. High-speed video and force plate data were collected for fastballs from each pitcher. Average ball speed was 25 m/sec. Peak vertical ground reaction force averaged 139 % body weight (BW), peak anterior force averaged 24 %BW, and the medially directed component of the ground reaction force averaged 42 %BW. Loading rates to peak force in all 3 directions were high. Preventive and rehabilitative protocols for windmill softball pitchers can begin to be improved on the basis of knowledge of the magnitudes and times to peak forces under the stride foot.

Throwing Arm Dominance in Collegiate Baseball Pitching A Biomechanical Study

Background: Left-handed individuals make up about 10% of the general population, yet left-handers comprise approximately 30% of the pitching staffs in Major League and Division I college baseball. Despite speculation regarding differences between right- and left-handed pitchers, distinction between right- and left-handed pitching mechanics has not been documented in the literature at any level of play. Hypothesis: Left-hand–dominant pitchers display similar pitching mechanics and upper extremity joint loads when compared to their right-hand–dominant counterparts. Study Design: Controlled laboratory study. Methods: Three-dimensional, high-speed (240-Hz) video data were collected on fastballs from 84 collegiate baseball pitchers. Kinematic parameters related to pitching mechanics and resultant kinetics on the throwing shoulder and elbow were calculated. The 28 left-handed pitchers in the database were matched with 28 right-handed pitchers for age, height, mass, and ball velocity, and paired t tests were used to compare the kinematic and kinetic parameters. Results: Six parameters were found to have statistically significant differences between left- and right-handed pitchers. Passive nonthrowing shoulder external rotation (right, 113° ± 9°; left, 124° ± 8°), elbow flexion at stride-foot contact (right, 79° ± 16°; left, 94° ± 20°), and shoulder abduction during acceleration (right, 72° ± 11°; left, 105° ± 8°) were greater in left-handed pitchers than right-handed pitchers. Shoulder abduction at stride-foot contact (right, 115° ± 13°; left, 73° ± 10°), shoulder horizontal abduction at stride-foot contact (right, 25° ± 12°; left, 15° ± 12°), and peak horizontal adduction angular velocity (right, 707 ± 185 deg/s; left, 551 ± 160 deg/s) were less for the left-handed pitchers. Conclusion: Biomechanical differences between left- and right-handed pitchers have been demonstrated in a collegiate population. Clinical Relevance: The results of the current study indicate that left-handed pitchers may be at increased risk for certain shoulder injuries compared with their right-handed counterparts. Information has been provided for athletes, coaches, and sports medicine providers to further improve preventive and rehabilitative protocols for college pitchers. The results of the study also suggest that different normative data sets may need to be developed for left- and right-handed pitchers, independently of one another.

Lower-Extremity Ground Reaction Forces in Collegiate Baseball Pitchers

Abstract Guido, JA Jr and Werner, SL. Lower-extremity ground reaction forces in collegiate baseball pitchers. J Strength Cond Res 26(7): 1782–1785, 2012—The purpose of this study was to investigate ground reaction forces (GRF) in collegiate baseball pitchers and their relationship to pitching mechanics. Fourteen healthy collegiate baseball pitchers participated in this study. High-speed video and force plate data were collected for fastballs from each pitcher. The average ball speed was 35 ± 3 m/sec (78 ± 7 mph). Peak GRFs of 245 ± 20% body weight (BW) were generated in an anterior or braking direction to control descent. Horizontal GRFs tended to occur in a laterally directed fashion, reaching a peak of 45 ± 63% BW. The maximum vertical GRF averaged 202 ± 43% BW approximately 45 milliseconds after stride foot contact. A correlation between braking force and ball velocity was evident. Because of the downward inclination and rotation of the pitching motion, in addition to volume, shear forces may occur in the musculoskeletal tissues of the stride limb leading to many of the lower-extremity injuries seen in this athletic population.