Kinematic and kinetic differences between left-and right-handed professional baseball pitchers.

While 10% of the general population is left-handed, 27% of professional baseball pitchers are left-handed. Biomechanical differences between left- and right-handed college pitchers have been previously reported, but these differences have yet to be examined at the professional level. Therefore, the purpose of this study was to compare pitching biomechanics between left- and right-handed professional pitchers. It was hypothesised that there would be significant kinematic and kinetic differences between these two groups. Pitching biomechanics were collected on 96 left-handed pitchers and a group of 96 right-handed pitchers matched for age, height, mass and ball velocity. Student t-tests were used to identify kinematic and kinetic differences (p < 0.05). Of the 31 variables tested, only four were found to be significantly different between the groups. Landing position of the stride foot, trunk separation at foot contact, maximum shoulder external rotation and trunk forward tilt at ball release were all significantly greater in right-handed pitchers. The magnitude of the statistical differences found were small and not consistent with differences in the two previous, smaller studies. Thus, the differences found may be of minimal practical significance and mechanics can be taught the same to all pitchers, regardless of throwing hand.

Do Mound Height and Pitching Distance Affect Youth Baseball Pitching Biomechanics?

BACKGROUND: Pitching injuries continue to be a serious problem, with adolescents now representing the group with the most injuries. Some have proposed that lowering or eliminating the pitching mound in youth baseball may reduce joint stress and subsequent injuries. Another potential risk factor is advancing from youth to adult pitching distance without an intermediate distance. HYPOTHESES: It was hypothesized that for a group of young pitchers, pitching kinetics and kinematics would change with mound height. It was also hypothesized that pitching kinetics and kinematics would change with pitching distance. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty-one young (12.6 ± 0.5 years) baseball pitchers pitched 5 full-effort fastballs each from 5 different conditions, in random order: 14.02-, 16.46-, and 18.44-m distances from a 25 cm-high mound, 16.46-m distance from a 15 cm-high mound, and 16.46-m distance from flat ground. Pitching biomechanical values were collected with a 12-camera automated motion capture system. Ball velocity and 31 other parameters were computed for each pitch. Data were compared between the 3 mound heights at 16.46 m by use of repeated-measures analysis of variance and paired post hoc t tests ( P < .05). Similarly, data were compared between the 3 distances from the 25-cm mound via repeated-measures analysis of variance and paired post hoc t tests ( P < .05). RESULTS: No differences were found in ball velocity, shoulder kinetics, or elbow kinetics associated with mound height. Ten kinematic parameters differed with mound height, including 8 parameters at lead foot contact. Maximum shoulder horizontal adduction torque and maximum shoulder anterior force increased with pitching distance. Only 3 kinematic parameters showed significant differences with pitching distance. CONCLUSION: The hypothesis that shoulder and elbow kinetics would change with mound height was not supported by the data. Several kinematic differences were found, but the majority were at lead foot contact before the rapid, dynamic phases of pitching. Change in pitching distance was associated with slight increase in shoulder kinetics as well as a few kinematic differences. CLINICAL RELEVANCE: Lowering or eliminating pitching mounds in youth baseball would not significantly decrease joint stress and injury risk to young pitchers. However, when available, transition from 14.02-m to 16.46-m to 18.44-m pitching distance may reduce stress on the young throwing shoulder.

Do baseball pitchers improve mechanics after biomechanical evaluations?

The purpose of this study was to determine how often flaws in pitching mechanics identified from biomechanical analysis are corrected. The biomechanics of 46 baseball pitchers were evaluated twice, with an average of 12 months (range 2-48 months) between evaluations. Pitchers were healthy at the time of both evaluations, competing at the high school, college, minor league or Major League level. After warming up, each participant pitched 10 full-effort fastballs. Automated three-dimensional motion analysis was used to compute eight kinematic parameters which were compared with a database of elite professional pitchers. Flaws-defined as deviations from the elite range-were explained to each participant or coach after his initial evaluation. Data from the second evaluation revealed that 44% of all flaws had been corrected. Flaws at the instant of foot contact (stride length, front foot position, shoulder external rotation, shoulder abduction, elbow flexion) or slightly after foot contact (time between pelvis rotation and upper trunk rotation) seemed to be corrected more often than flaws near the time of ball release (knee extension and shoulder abduction). Future research may determine which level athletes or which training methods are most effective for correcting flaws.

Changes in Youth Baseball Pitching Biomechanics: A 7-Year Longitudinal Study.

BACKGROUND: Pitching biomechanics are associated with performance and risk of injury in baseball. Previous studies have identified biomechanical differences between youth and adult pitchers but have not investigated changes within individual young pitchers as they mature. HYPOTHESIS: Pitching kinematics and kinetics will change significantly during a youth pitcher's career. STUDY DESIGN: Descriptive laboratory study. METHODS: Pitching biomechanics were captured in an indoor laboratory with a 12-camera, 240-Hz motion analysis system for 51 youth pitchers who were in their first season of organized baseball with pitching. Each participant was retested annually for the next 6 years or until he was no longer pitching. Thirty kinematic and kinetic parameters were computed and averaged for 10 fastballs thrown by each player. Data were statistically analyzed for the 35 participants who were tested at least 3 times. Within-participant changes for each kinematic and kinetic parameter were tested by use of a mixed linear model with random effects ( P < .05). Least squares means for sequential ages were compared via Tukey's honestly significant difference test ( P < .05). RESULTS: Three kinematic parameters that occur at the instant of foot contact-stride length, lead foot placement to the closed side, and trunk separation-increased with age. With age, shoulder external rotation at foot contact decreased while maximum shoulder external rotation increased. Shoulder and elbow forces and torques increased significantly with age. Year-to-year changes were most significant between 9 and 13 years of age for kinematics and between 13 and 15 years for normalized kinetics (ie, scaled by bodyweight and height). CONCLUSION: During their first few years, youth pitchers improve their kinematics. Elbow and shoulder kinetics increase with time, particularly after age 13. Thus, prepubescent pitchers may work with their coaches to improve the motions and flexibility of the players' bodies and the paths of their arms. Once proper mechanics are developed, adolescent pitchers can focus more on improving strength and power.

Biomechanical Analysis of Weighted-Ball Exercises for Baseball Pitchers.

BACKGROUND: Weighted-ball throwing programs are commonly used in training baseball pitchers to increase ball velocity. The purpose of this study was to compare kinematics and kinetics among weighted-ball exercises with values from standard pitching (ie, pitching standard 5-oz baseballs from a mound). HYPOTHESIS: Ball and arm velocities would be greater with lighter balls and joint kinetics would be greater with heavier balls. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty-five high school and collegiate baseball pitchers experienced with weighted-ball throwing were tested with an automated motion capture system. Each participant performed 3 trials of 10 different exercises: pitching 4-, 5-, 6-, and 7-oz baseballs from a mound; flat-ground crow hop throws with 4-, 5-, 6-, and 7-oz baseballs; and flat-ground hold exercises with 14- and 32-oz balls. Twenty-six biomechanical parameters were computed for each trial. Data among the 10 exercises were compared with repeated measures analysis of variance and post hoc paired t tests against the standard pitching data. RESULTS: Ball velocity increased as ball mass decreased. There were no differences in arm and trunk velocities between throwing a standard baseball and an underweight baseball (4 oz), while arm and trunk velocities steadily decreased as ball weight increased from 5 to 32 oz. Compared with values pitching from a mound, velocities of the pelvis, shoulder, and ball were increased for flat-ground throws. In general, as ball mass increased arm torques and forces decreased; the exception was elbow flexion torque, which was significantly greater for the flat-ground holds. There were significant differences in body positions when pitching on the mound, flat-ground throws, and holds. CONCLUSIONS: While ball velocity was greatest throwing underweight baseballs, results from the study did not support the rest of the hypothesis. Kinematics and kinetics were similar between underweight and standard baseballs, while overweight balls correlated with decreased arm forces, torques, and velocities. Increased ball velocity and joint velocities were produced with crow hop throws, likely because of running forward while throwing. CLINICAL RELEVANCE: As pitching slightly underweight and overweight baseballs produces variations in kinematics without increased arm kinetics, these exercises seem reasonable for training pitchers. As flat-ground throwing produces increased shoulder internal rotation velocity and elbow varus torque, these exercises may be beneficial but may also be stressful and risky. Flat-ground holds with heavy balls should not be viewed as enhancing pitching biomechanics, but rather as hybrid exercises between throwing and resistance training.