The Clinician's Guide to Baseball Pitching Biomechanics.

CONTEXT: Improper baseball pitching biomechanics are associated with increased stresses on the throwing elbow and shoulder as well as an increased risk of injury. EVIDENCE ACQUISITION: Previous studies quantifying pitching kinematics and kinetics were reviewed. STUDY DESIGN: Clinical review. LEVEL OF EVIDENCE: Level 5. RESULTS: At the instant of lead foot contact, the elbow should be flexed approximately 90° with the shoulder at about 90° abduction, 20° horizontal abduction, and 45° external rotation. The stride length should be about 85% of the pitcher's height with the lead foot in a slightly closed position. The pelvis should be rotated slightly open toward home plate with the upper torso in line with the pitching direction. Improper shoulder external rotation at foot contact is associated with increased elbow and shoulder torques and forces and may be corrected by changing the stride length and/or arm path. From foot contact to maximum shoulder external rotation to ball release, the pitcher should demonstrate a kinematic chain of lead knee extension, pelvis rotation, upper trunk rotation, elbow extension, and shoulder internal rotation. The lead knee should be flexed about 45° at foot contact and 30° at ball release. Corrective strategies for insufficient knee extension may involve technical issues (stride length, lead foot position, lead foot orientation) and/or strength and conditioning of the lower body. Improper pelvis and upper trunk rotation often indicate the need for core strength and flexibility. Maximum shoulder external rotation should be about 170°. Insufficient external rotation leads to low shoulder internal rotation velocity and low ball velocity. Deviation from 90° abduction decreases the ability to achieve maximum external rotation, increases elbow torque, and decreases the dynamic stability in the glenohumeral joint. CONCLUSION: Improved pitching biomechanics can increase performance and reduce risk of injury. SORT: Level C.

Biomechanical effects of foot placement during pitching.

Baseball coaches often focus on the landing position of a pitcher's front foot as a key aspect of mechanics. Furthermore, controversy persists regarding positioning the rear foot on the first base or third base end of the rubber. The purpose of this study was to determine the effect of rear and front foot placement on pitching biomechanics. Our hypotheses were that there would be significant kinematic and kinetic differences associated with foot placement. This was a retrospective review including 144 healthy right-handed adult baseball pitchers divided into groups based on their rear and front foot placements: first base open (1B-Open), first base closed (1B-Closed), third base open (3B-Open), and third base closed (3B-Closed). Two-way ANOVAs detected no statistically significant main effects for kinetic variables but several for kinematic variables. Open pitchers had less shoulder abduction at the time of ball release and greater maximum shoulder internal rotation velocity in comparison with closed pitchers. They also had less forearm pronation at the time of ball release and greater maximum elbow extension velocity. Additional statistically significant results were found; however, low effect sizes may lessen the clinical significance of many of the results.

The relationship between variability in baseball pitching kinematics and consistency in pitch location.

The purpose of this study was to explore the relationship between variability in pitching kinematics and consistency in pitch location. Data were collected for 47 healthy baseball pitchers throwing ten full-effort fastballs to the centre of the strike zone. For each pitch, 20 kinematic parameters were calculated with an automated motion capture system while pitch location was measured with a PITCHf/x system. Variability of each kinematic parameter was defined for each pitcher as the standard deviation among his fastballs thrown. For calculating consistency, each pitcher's mean pitch location was first calculated. The distances from each individual pitch to the mean pitch location were then found for each pitcher tested. A consistency metric was then calculated for each pitcher by averaging these distances. A multiple linear regression model was developed using stepwise regression with backwards elimination. The resulting model explained 58% of the variance in the consistency metric and included five parameters, three at foot contact (upper trunk tilt, shoulder abduction, and shoulder horizontal abduction) and two at time of maximum shoulder external rotation (shoulder external rotation and shoulder horizontal adduction). Reducing variability at the shoulder during the early portions of the pitching motion may improve consistency of ball location.

The influence of baseball pitching distance on pitching biomechanics, pitch velocity, and ball movement.

OBJECTIVES: To determine whether increasing pitching distance for adult baseball pitchers would affect their upper extremity kinetics, full-body kinematics, and pitched ball kinematics (ball velocity, duration of ball flight, vertical and horizontal break, strike percentage). DESIGN: Controlled laboratory study. METHODS: Twenty-six collegiate baseball pitchers threw sets of five full-effort fastballs from three different pitching distances (18.44m, 19.05m, 19.41m) in a randomized order. Ball velocity, horizontal and vertical break, duration of ball flight, and strike percentage were computed by a ball tracking system, while pitching kinetics and kinematics were calculated with a 12-camera optical motion capture system. Repeated measures analysis of variance was utilized to detect significant differences among the three different pitching distances (p<0.05). RESULTS: No significant differences in pitching kinetics and kinematics were observed among the varying pitching distances. Ball velocity and strike percentage were also not significantly different among the pitching distances, however, the duration of ball flight and horizontal and vertical break significantly increased with pitching distance. CONCLUSIONS: Increasing pitching distance may not alter upper extremity kinetics, full-body kinematics, ball velocity or strike percentage in adult pitchers. However, as pitching distance increases the duration of ball flight and amount of horizontal and vertical break also increase. Increased ball flight duration could be an advantage for the hitter while increased ball break could help the pitcher. In conclusion, it is unlikely that moving the mound backwards would significantly affect pitching biomechanics and injury risk; however, the effects on pitching and hitting performance are unknown.

Baseball Pitching Biomechanics Shortly After Ulnar Collateral Ligament Repair.

BACKGROUND: The probability of returning to competition for injured baseball pitchers is similar after ulnar collateral ligament (UCL) repair as after UCL reconstruction, but the time to return is significantly quicker after UCL repair. Previous research has found no differences in pitching biomechanics between pitchers with and without a history of UCL reconstruction, but pitching biomechanics after UCL repair has not been studied. HYPOTHESIS: There will be significant differences in pitching biomechanics between pitchers returning to play after UCL repair and pitchers with no injury history. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 33 pitchers were tested shortly after UCL repair (9.8 ± 2.6 months) and compared with a matched group of 33 uninjured pitchers. Each group comprised 14 college pitchers and 19 high school pitchers. Shoulder and elbow passive ranges of motion were measured. The biomechanics of 10 fastballs was then collected using a 12-camera automated motion capture system. Ball velocity was measured using a separate 3-camera optical tracking system. Data were compared between the UCL repair group and the control group using the Student t test (significance set at P < .05). RESULTS: There were no differences in passive range of motion or fastball velocity between the 2 groups. There were no differences in joint kinetics during pitching, but 3 kinematic variables showed significant differences. Specifically, the UCL repair group produced less elbow extension (flexion: 27° ± 6° vs 24° ± 4°, respectively; P = .03), less elbow extension velocity (2442 ± 367 vs 2631 ± 292 deg/s, respectively; P = .02), and less shoulder internal rotation velocity (6273 ± 1093 vs 6771 ± 914 deg/s, respectively; P = .049 ) compared with the control group. CONCLUSION: Elbow extension, elbow velocity, and shoulder velocity differed between pitchers with a recent history of UCL repair and a matched control group, but it is unclear whether this has clinical significance, as there were no differences in ball velocity and passive range of motion. Furthermore, it is unknown whether these few differences in pitching biomechanics resolve with time. CLINICAL RELEVANCE: Elbow and shoulder kinematics during pitching might not be completely regained within the first year after UCL repair, although passive range of motion and pitch velocity show no difference in comparison to other healthy pitchers.

The influence of mound height on baseball movement and pitching biomechanics.

OBJECTIVES: To determine whether mound height is associated with baseball movement (velocity, spin and break) and baseball pitching biomechanics (kinematics and kinetics). DESIGN: Controlled laboratory study. METHODS: Twenty collegiate baseball pitchers threw five fastballs and five curveballs from four different mound heights (15cm, 20cm, 25cm, 30cm) in a randomized order. Ball movement was computed by a ball tracking system, while pitching biomechanics were calculated with an 11-camera optical motion capture system. Repeated measures analysis of variance was utilized to detect significant differences among the four different mound heights (p<0.05) for the fastball and curveball pitches. RESULTS: There were no significant differences observed for ball movement. There were seven significant kinematic differences for fastballs and eight kinematic differences for curveballs. Although these differences were statistically significant, the magnitudes were small, with most joint angles changing by less than 2°. There were no significant kinetic differences for curveballs, but five kinetic parameters (elbow varus torque, elbow flexion torque, elbow proximal force, shoulder internal rotation torque, and shoulder anterior force) varied with mound height for fastballs. In general, fastball kinetics were 1%-2% less from the lowered (15cm, 20cm) mounds than from the standard (25cm) or raised (30cm) mounds. CONCLUSIONS: Lowering the mound may not affect a pitcher's ball movement, but may slightly reduce shoulder and elbow kinetics, possibly reducing the risk of injury.

Fastball Velocity and Elbow-Varus Torque in Professional Baseball Pitchers.

CONTEXT: High loads in the elbow during baseball pitching can lead to serious injuries, including injuries to the ulnar collateral ligament. These injuries have substantial implications for individual pitchers and their teams, especially at the professional level of competition. With a trend toward increased ball velocity in professional baseball, controversy still exists regarding the strength of the relationship between ball velocity and elbow-varus torque. OBJECTIVE: To examine the relationship between fastball velocity and elbow-varus torque in professional pitchers using between- and within-subjects statistical analyses. DESIGN: Cross-sectional study. SETTING: Motion-analysis laboratory. PATIENTS OR OTHER PARTICIPANTS: Using the previously collected biomechanical data of 452 professional baseball pitchers, we performed a retrospective analysis of the 64 pitchers (52 right-hand dominant, 12 left-hand dominant; age = 21.8 ± 2.0 years, height = 1.90 ± 0.05 m, mass = 94.6 ± 7.8 kg) with fastball velocity distributions that enabled between- and within-subjects statistical analyses. MAIN OUTCOME MEASURE(S): We measured ball velocity using a radar gun and 3-dimensional motion data using a 12-camera automated motion-capture system sampling at 240 Hz. We calculated elbow-varus torque using inverse-dynamics techniques and then analyzed the relationship between ball velocity and elbow torque using both a simple linear regression model and a mixed linear model with random intercepts. RESULTS: The between-subjects analyses displayed a weak positive association between ball velocity and elbow-varus torque (R2 = 0.076, P = .03). The within-subjects analyses showed a considerably stronger positive association (R2 = 0.957, P < .001). CONCLUSIONS: When comparing 2 professional baseball pitchers, higher velocity may not necessarily indicate higher elbow-varus torque due to the confounding effects of pitcher-specific differences (eg, detailed anthropometrics and pitching mechanics). However, within an individual pitcher, higher ball velocity was strongly associated with higher elbow-varus torque.

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.

Differences Among Overhand, 3-Quarter, and Sidearm Pitching Biomechanics in Professional Baseball Players.

The purpose of this study was to assess biomechanical differences among overhand, 3-quarter, and sidearm arm slot professional baseball pitchers. It was hypothesized that kinematic and kinetic differences would be found among the 3 groups, with sidearm pitchers demonstrating greater movement along the transverse plane and overhead pitchers demonstrating greater movement along the sagittal plane. Based upon arm slot angle at ball release, 30 overhand, 156 three-quarter, and 21 sidearm pitchers were tested using a 240-Hz motion analysis system, and 37 kinematic and kinetic parameters were calculated. One-way analyses of variance (α = .01) was employed to assess differences among groups. The comparisons showed the sidearm group had less shoulder anterior force, whereas the overhand group had the least elbow flexion torque. At ball release, trunk contralateral tilt and shoulder abduction were greatest for the overhand group and least for sidearm group. Additionally, the sidearm group demonstrated the lowest peak knee height, most closed foot angle, greatest pelvis angular velocity, and shoulder external rotation. The overhand group had the greatest elbow flexion at foot contact and greatest trunk forward tilt at ball release. The greater elbow flexion torque and shoulder external rotation exhibited by sidearm pitchers may increase their risk of labral injury. Conversely, the lower shoulder anterior force in sidearm pitchers may indicate lower stress on shoulder joint capsule and rotator cuff.

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.

The effects of baseball bat mass properties on swing mechanics, ground reaction forces, and swing timing.

Swing trajectory and ground reaction forces (GRF) of 30 collegiate baseball batters hitting a pitched ball were compared between a standard bat, a bat with extra weight about its barrel, and a bat with extra weight in its handle. It was hypothesised that when compared to a standard bat, only a handle-weighted bat would produce equivalent bat kinematics. It was also hypothesised that hitters would not produce equivalent GRFs for each weighted bat, but would maintain equivalent timing when compared to a standard bat. Data were collected utilising a 500 Hz motion capture system and 1,000 Hz force plate system. Data between bats were considered equivalent when the 95% confidence interval of the difference was contained entirely within ±5% of the standard bat mean value. The handle-weighted bat had equivalent kinematics, whereas the barrel-weighted bat did not. Both weighted bats had equivalent peak GRF variables. Neither weighted bat maintained equivalence in the timing of bat kinematics and some peak GRFs. The ability to maintain swing kinematics with a handle-weighted bat may have implications for swing training and warm-up. However, altered timings of kinematics and kinetics require further research to understand the implications on returning to a conventionally weighted bat.