Pitch velocity is a predictor of medial elbow distraction forces in the uninjured high school-aged baseball pitcher

Kinematic Modeling of Pitch Velocity in High School and Professional Baseball Pitchers: Comparisons With the Literature

Background

Kinematic parameters predictive of pitch velocity have been evaluated in adolescent and collegiate baseball pitchers; however, they have not been established for high school or professional pitchers.

Purpose

To create multiregression models using anthropometric and kinematics features most predictive for pitch velocity in high school and professional pitchers and compare them with prior multiregression models evaluating other playing levels.

Study Design

Descriptive laboratory study.

Methods

High school (n = 59) and professional (n = 337) baseball pitchers threw 8 to 12 fastballs while being evaluated with 3-dimensional motion capture (480 Hz). Using anthropometric and kinematic variables, multiregression models for pitch velocity were created for each group. A systematic review was conducted to determine previous studies that established kinematic models for ball velocity in youth, high school, and collegiate pitchers.

Results

Leg length was predictive of pitch velocity for high school and professional pitchers (P < .001 for both). When compared with previously established models for pitch velocity, almost all groups were distinct from one another when assessing age (P maximum < .001), weight (P max = .0095), and pitch velocity (P max < .001). Stride length was a significant predictor for the youth/high school pitchers, as well as the current study's high school and professional pitchers (P < .001 for all). Maximal shoulder external rotation (collegiate: P = .001; professional: P < .001) and maximal elbow extension velocity (high school/collegiate: P = .024; collegiate: P < .001; professional: P = .006) were shared predictors for the collegiate and current study's professional group multiregression models. Trunk flexion at ball release was a commonly shared predictor in the youth/high school (P = .04), high school/collegiate (P = .003), collegiate (P < .001), and the current study's professional group (P < .001).

Conclusion

Youth, high school, collegiate, and professional pitchers had unique, predictive kinematic and anthropometric features predictive of pitch velocity. Leg length, stride length, trunk flexion at ball release, and maximal shoulder external rotation were predictive features that were shared between playing levels.

Clinical Relevance

Coaches, clinicians, scouts, and pitchers can consider both the unique and the shared predictive features at each playing level when attempting to maximize pitch velocity.

An Analysis of Intrapitch Variation in Joint and Segment Velocities With Throwing Arm Kinetics in High School and Professional Baseball Pitchers

BACKGROUND

Improper sequencing order of maximal joint and segment velocities has been identified as an important predictor for both throwing arm kinetics and ball velocity.

PURPOSE

To investigate the intrapitcher variation of maximal segment velocities and the relationship to throwing arm kinetics and ball velocity in high school (HS) and professional (PRO) pitchers.

STUDY DESIGN

Descriptive laboratory study.

METHODS

HS (n = 59) and PRO (n = 338) pitchers, instructed to throw 8 to 12 fastball pitches, were evaluated with 3-dimensional motion capture (480 Hz). Maximal joint and segment velocities were calculated for each pitch, and the standard deviation of the maxima was calculated per pitcher. These standard deviations were used to classify pitchers as "low variance" or "high variance" for each segmental velocity subgroup, "overall low variance" or "overall high variance" based on cumulative segment velocity variation, or "population," with any pitcher eligible to be included in multiple subcategories. Maximal velocities and throwing arm kinetics were compared among the various subgroups.

RESULTS

The HS low-variance shoulder internal rotation velocity subgroup (4949 ± 642 deg/s) had significantly lower maximal shoulder internal rotation velocity compared with HS population (5774 ± 1057 deg/s) (P < .001); similar findings were observed for PROs (5269 ± 835 vs 5824 ± 1076 deg/s; P < .001), as well as lower shoulder superior force compared with the PRO population (14.8% ± 8.8% vs 17.8% ± 8.8% body weight; P = .001). The PRO low-variance lead knee extension velocity subgroup had significantly lower maximal lead knee extension velocity (216 ± 135 vs 258 ± 125 deg/s; P = .001) and shoulder distractive force (111.5% ± 14.4% vs 115.6% ± 15.9% body weight; P = .003) compared with the PRO population. The PRO overall low-variance subgroup had significantly lower shoulder distractive force (111.8% ± 14.1% vs 119.6% ± 15.5% body weight; P = .008) and elbow anterior force (40.6% ± 5.0% vs 43.6% ± 6.2% body weight; P = .008) compared with the PRO overall high-variance subgroup.

CONCLUSION

HS and PRO pitchers with low variance for joint and segment velocities achieved significantly lower maximal velocities in the subgroup of interest, while preserving ball velocity. PRO pitchers with overall low variance among multiple maximal joint and segment velocities demonstrated decreased shoulder distractive and elbow anterior force.

CLINICAL RELEVANCE

PRO pitchers with low intrapitch variation in maximal joint and segment velocities may be viewed as kinetically conservative throwers. These pitchers with similarly maintained mechanics between pitches may have an increasingly regimented form that preserves kinetic forces about the throwing arm. The opposite may be true for PRO pitchers with increased variability in segmental velocities during their pitching motion, as they showed increased throwing arm kinetics including shoulder distractive and elbow anterior force compared with the overall low-variance group, theoretically increasing their risk of injury.

Differences in Anatomic Adaptation and Injury Patterns Related to Valgus Extension Overload in Overhead Throwing Athletes

The purpose of our study was to determine differences in adaptative and injury patterns in the elbow related to valgus extension overload (VEO) in overhead throwing athletes by age. A total of 86 overhead throwing athletes and 23 controls underwent MRI or MR arthrography (MRA) of the elbow. Throwing athletes were divided by age into three groups: ≤16 years (26 subjects), 17-19 years (25 subjects), and ≥20 years (35 subjects). Consensus interpretation of each MRI was performed, with measurements of ulnar collateral ligament (UCL) thickness and subchondral sclerosis at the radial head, humeral trochlea, and olecranon process. A higher frequency of apophyseal and stress injuries was seen in adolescent athletes and increased incidence of soft tissue injuries was observed in older athletes. Early adaptive and degenerative changes were observed with high frequency independent of age. Significant differences were observed between athletes and controls for UCL thickness (p < 0.001) and subchondral sclerosis at the radial head (p < 0.001), humeral trochlea (p < 0.001), and olecranon process (p < 0.001). Significant differences based on athlete age were observed for UCL thickness (p < 0.001) and subchondral sclerosis at the olecranon process (p = 0.002). Our study highlights differences in anatomic adaptations related to VEO at the elbow between overhead throwing athletes and control subjects, as well as across age in throwing athletes.

Neurocognitive and Reactive Return to Play Testing Protocol in Overhead Athletes Following Upper Extremity Injury

The incidence of upper extremity (UE) injuries in sport, particularly with the shoulder and elbow in baseball/softball players, appears to be increasing yearly, especially in younger age athletes. Improving the objective criteria and testing methods used to determine return to play (RTP) readiness following non-operative or post-operative management of UE injuries is one aspect of the rehabilitation process that may significantly help in reducing reinjury rates. Currently, the majority of clinicians are still using post operative time frame and/or strength/range of motion as their main criteria for clearance to RTP following UE injury. This demonstrates an inadequate reflection of the actual unpredictable, dynamic environment athletes are returning to participate in. In our clinical experiences, objective testing to allow for clearance to sport participation should incorporate neurocognitive and reactive testing to promote improvements in the athlete's ability to dual task and focus/concentrate on the multi-dimensional tasks at hand. We know that neuroplastic changes occur following UE injury resulting in decreased proprioception and increased motor activation with simple UE tasks. Currently the research on UE return to play testing is limited. The purpose of this clinical commentary was to describe the utilization and provide reference values for a series of reactive neurocognitive UE tests, to assist with RTP, in high school and collegiate overhead athletes (baseball and softball) utilizing the Blaze Pod light system. The use of a more dynamic reactive testing battery may decrease the reinjury rates when an athlete is cleared for participation by measuring readiness in chaotic circumstances that are more reflective of the sporting environment the athlete is working to return to resulting in a greater sense of confidence, performance and prevention of reinjuries.

Incidence and Characteristics of Elbow Injury in Japanese Youth Baseball Players: Comparison Between 2011 and 2021

Background

Little League elbow, including humeral epicondylitis and osteochondritis dissecans, is a severe throwing injury in school-aged pitchers. Recent rule revisions have been implemented, and thus, prevention awareness may have increased.

Purpose

To compare the incidence of elbow injury in 2011 from a previous study with that in 2021 and examine changes in the incidence and characteristics of players with elbow injuries.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

A survey based on the 2011 survey was conducted from September 1 to December 31, 2021, among 4060 third- to sixth-grade Little League players belonging to 203 teams in Kyoto, Japan. This survey included a 23-item checklist on physical condition and injury. The participants were classified into 2 groups according to the presence or absence of an elbow injury in the dominant arm during the season. The Wilcoxon rank-sum test was conducted to compare differences in basic information between the 2 groups. We also compared the differences in the 23 checklist items between the 2 groups using the chi-square or Fisher exact probability test.

Results

Overall, 98 teams (1335 players; age range, 8-12 years) returned the questionnaires (collection rate, 32.9%). The final analysis population (excluding incomplete questionnaires) was 678 (mean age, 10.6 ± 1.1 years). Elbow injuries accounted for 30.7% of all injury sites in the players. Overall, 61 players (9.0%) reported elbow injuries in 2021 compared with 19.1% of the players in the 2011 survey (P < .01) A significantly higher percentage of players with elbow injuries had elbow pain in extension (item 2 on the survey checklist, P < .001) and flexion (item 4, P < .0024), were regular players (item 5, P = .0288), played baseball under fatigue (item 8, P = .0028), and had lower and upper limb inflexibility (item 17, P = .0379; item 18, P = .0146; and item 22, P = .0085).

Conclusion

Study findings indicated that the incidence of elbow injuries has decreased significantly over the past 10 years, although the elbow joint still accounted for almost one-third of all injuries in Japanese youth baseball players.

Are 4D Motion Sensors Valid and Reliable for Studying Baseball Pitching?

BACKGROUND

Baseball pitching injuries are on the rise. Inertial measurement units (IMUs) provide immediate feedback to players and coaches, allowing for collection outside of the traditional laboratory setting with real-world application. The 4D Motion system provides kinematics throughout the pitching motion and may be beneficial for individualized programs in the throwing athlete. A systematic analysis of these sensors has not been completed.

PURPOSE

To evaluate the validity of the 4D Motion IMU system for analyzing the baseball pitching motion compared with marker-based motion capture, and evaluate the internal reliability and consistency of the device.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten high school pitchers participated in this study (10 male; 9 right-hand dominant; mean age, 16.6 ± 1.3 years; mean body mass index, 24.1 ± 3.9). Participants were simultaneously outfitted with six 4D Motion IMU sensors and retroreflective markers. The pitchers threw fastballs at maximum effort off a mound at the standard height and distance. A comparison was made between the IMUs and corresponding motion capture values for shoulder external rotation, elbow flexion, chest extension, pelvis and chest rotation velocity, and rotation acceleration.

RESULTS

Significant differences were found for 5 of 7 metrics analyzed. The IMU overreported most metrics, except for elbow flexion and pelvis rotation angular acceleration, where both positive and negative errors were observed. The root mean square error and percentage errors indicated smaller discrepancies for chest extension (4°± 5°) and pelvis (38 ± 19 deg/s) and chest (96 ± 42 deg/s) rotation velocity, with elbow flexion having the largest variance (21°± 9°).

CONCLUSION

The values of the 4D Motion IMU system should not be considered equivalent when compared with marker-based motion capture studies. The system lacked internal consistency and reliability, with angular velocities being the most consistent. Caution should be used when using the metrics provided by an IMU-based system for individualized monitoring.

CLINICAL RELEVANCE

If found valid and reliable, IMUs could be used for longitudinal workload monitoring, individualized throwing and rehabilitation programs, and ultimately injury prevention. This study demonstrates that the data obtained from a 4D Motion system using Gen 3 sensors are not equivalent to the data obtained from a marker-based motion capture system.

Collegiate baseball pitchers demonstrate a relationship between ball velocity and elbow varus torque, both within and across pitchers

High elbow varus torque during baseball pitching has been identified as a potential cause of ulnar collateral ligament injury in baseball pitchers. In general, elbow varus torque increases as ball velocity increases across pitchers. However, studies incorporating within-subject analyses report that not all professional pitchers have a positive relationship between elbow varus torque and ball velocity (T-V relationship). It remains unknown whether collegiate pitchers show the same trend as professionals in their T-V relationships. The current study investigated the T-V relationship of collegiate pitchers focusing on both across and within pitchers. Division 1 collegiate pitchers (n = 81) were assessed for elbow torque and ball velocity during pitching. Both across- and within-pitcher T-V relationships were significant (p < 0.05) using linear regression. However, more variance in elbow varus torque was explained using the within-pitcher relationship (R2 = 0.29) than the across-pitcher relationship (R2 = 0.05). Of the 81 pitchers, nearly half (n = 39) had significant T-V relationships, while the other half (n = 42) did not. Our findings indicate that the T-V relationship should be assessed on an individual basis as T-V is pitcher-specific.

Clinical shoulder measurements related to joint loads in collegiate pitchers

Background

Pitchers are prone to upper extremity injury due to repetitive high joint loads. Clinical measures of shoulder strength and range of motion (ROM) have shown links to injury risk in pitchers, however, these factors have rarely been studied in relation to throwing joint loads. The purpose of this study was to identify which clinical ROM and isokinetic strength variables were related to peak shoulder and elbow joint torques in collegiate pitchers.

Methods

Thirty-three healthy collegiate pitchers participated in this study. Fastball velocity, shoulder concentric and eccentric strength, and passive shoulder ROM variables were analyzed using a Lasso regression to determine what factors influenced shoulder internal rotation torque and elbow varus torque.

Results

Fastball velocity was selected by the Lasso as indicator of increased shoulder and elbow torque. Passive shoulder external rotation ROM was also selected as an important factor in joint loading with increased shoulder external rotation ROM being related to lower joint loads. The bilateral ratio of shoulder internal rotator concentric strength was related to peak shoulder and elbow torques with an increase in the bilateral ratio of shoulder strength leading to reduced joint torques. Increases in the eccentric external rotator to concentric internal rotator strength (functional ratio) of the dominant arm and increases in dominant arm eccentric internal rotator strength were both related to increases in each joint torque.

Conclusion

Results from the study indicate that pitch speed, passive shoulder external rotation ROM, and the isokinetic shoulder strength profile including internal rotator strength and functional strength ratio of pitchers are related to joint loading during the pitch and may be important to monitor in relation to injury risk and/or during rehabilitation. These results provide insight into the role that both shoulder ROM and rotator cuff strength play in the dynamic stabilization of the elbow and shoulder during pitching.

Increased Pitch Velocity Is Associated With Throwing Arm Kinetics, Injury Risk, and Ulnar Collateral Ligament Reconstruction in Adolescent, Collegiate, and Professional Baseball Pitchers: A Qualitative Systematic Review

PURPOSE

To assess the relationship between pitch velocity and throwing arm kinetics, injury, and ulnar collateral ligament reconstruction (UCLr) among high school, collegiate, and professional baseball pitchers.

METHODS

The Cochrane Database of Systematic Reviews, the Cochrane Central Register of Controlled Trials, PubMed (2008-2019), and OVID/MEDLINE (2008-2019) were queried for articles that reported on pitch velocity predicting throwing arm kinetics, injury, or UCLr. The Methodological Index for Non-randomized Studies checklist was used to evaluate the quality of all included studies. Descriptive statistics with ranges were used to quantify data where appropriate.

RESULTS

A total of 24 studies examining 2,896 pitchers, with Level of Evidence II-V were included. Intergroup analysis noted pitch velocity was significantly correlated with elbow varus torque in high school (R² = 0.36), collegiate (R² = 0.29), and professional (R² = 0.076) pitchers. Elbow distraction force was positively associated with ball velocity in interpitcher analyses of high school (R² = 0.373), professional (R² = 0.175), and mixed-cohort evaluations (R² = 0.624). Intragroup analysis demonstrated a strong association between pitch velocity and elbow varus torque (R² = 0.922-0.957) and elbow distraction force (R² = 0.910) in professional pitchers. Faster ball velocity was positively associated with a history of throwing arm injury (R² = 0.194) in nonadult pitchers. In 2 studies evaluating professionals, injured pitchers had faster pitch velocity before injury compared with uninjured controls (P = .014; P = .0354). The need for UCLr was positively correlated with pitch velocity (R² = 0.036) in professional pitchers. The consequences of UCLr noted little to no decrease in pitch velocity.

CONCLUSIONS

Professional baseball pitchers with faster pitch velocity may be at the greatest risk of elbow injury and subsequent UCLr, potentially through the mechanism of increased distractive forces on the medial elbow complex. When a pitcher ultimately undergoes UCLr, decreases in pitching performance are unlikely, but may occur, which should encourage pitchers to caution against maximizing pitch velocity.

LEVEL OF EVIDENCE

Level IV, systematic review of Level II-IV studies.

Factors that Increase Elbow Stress in the Throwing Athlete: a Systematic Review of Biomechanical and Motion Analysis Studies of Baseball Pitching and Throwing

PURPOSE OF REVIEW

Elbow pain poses a unique challenge in the throwing athlete. Due to the high levels of elbow stress during the throwing motion, elbow injuries are common in throwers of all ages. There are several postulated factors believed to contribute increased stress to the throwing elbow. A detailed review of the published biomechanical studies evaluating the stresses experienced by the throwing elbow is needed. Here, we review these biomechanical studies to extrapolate the contributing factors that increase stress, the modifications that may reduce such stress, and the post-injury rehabilitation that optimizes outcomes and reduces recurrence.

RECENT FINDINGS

The biomechanical forces on the elbow have been further investigated delineated in recent work. Rotational malalignment of the shoulder, including both GIRD and decreased adduction, increases torque experienced by the elbow during pitching motions. Exact interactions between lower extremity, lumbopelvic or trunk rotation, and elbow forces during throwing remain uncertain with mixed results in recent literature. Pitch types may influence elbow stresses although delivery mechanism and distance thrown do not. Several biomechanical factors influence the stresses imparted on the throwing elbow. Throwing volume, proper throwing mechanics, and appropriate rehabilitation are likely to be to be the most influential on mitigating unnecessary stresses imparted to the elbow in the throwing athlete. A proper understanding of these factors may reduce the occurrence of these injuries in this population. Moreover, an understanding of proper rehabilitation following injury may ensure optimized results and reduce recurrence.

Kinetic and kinematic comparisons in high school pitchers with low and high pitch location consistency

BACKGROUND

Although ball velocity has often been associated with increased kinetics at the upper extremity and risk of injury in youth and adolescent pitchers, it is unclear if the performance metric pitch location consistency has any positive or negative associations with pitching kinetics.

METHODS

High school pitchers (n = 59) pitched 8-12 fastballs using 3D motion capture (480 Hz). Pitchers were divided into high-consistency (HiCon) and low-consistency (LoCon) groups based on the absolute center deviation of each pitcher's pitch to the center of the pitcher's mean pitch location. Ninety-five percent confidence ellipses with major and minor radii were constructed, and kinematics and kinetics were compared between groups.

RESULTS

Compared with LoCon pitchers, HiCon pitchers had decreased lead hip flexion at elbow extension (40° ± 12° vs. 52° ± 13°, respectively, P = .008), and at foot contact, decreased back hip extension (-1° ± 10° vs. -10° ± 13°, respectively, P = .038) and increased back hip internal rotation (9° ± 15° vs. -2° ± 15°, respectively, P = .043). LoCon pitchers achieved maximum lead hip flexion earlier in the pitch (61.3% ± 23.2% vs. 75.8% ± 15.1%, respectively, P = .039). A multiregression model predicted 0.49 of variance in pitch location consistency using kinematic inputs.

DISCUSSSION AND CONCLUSION

Pitchers who differ in pitch location consistency outcomes do not appear to demonstrate physiologically unsafe kinematics. High school pitchers who strive for improved pitch consistency can consider adjusting parameters of hip kinematics during early portions of the pitch.

The effects of relative trunk rotation velocity on ball speed and elbow and shoulder joint torques during baseball pitching

In baseball pitching, suppressing trunk rotation while rotating the pelvis in the early phase of arm cocking is important for throwing a fast ball. However, quantitative evaluation of trunk rotation during pitching has not been established, and its associations with elbow and shoulder torques are unclear. The purpose of this study was to examine the correlation of a new measure of trunk rotation suppression with ball speed and elbow and shoulder torques during pitching. Eighteen adult male baseball pitchers (21.7 ± 1.2 years old) participated. Three qualified pitches were analysed using a three-dimensional motion capture system. Trunk rotation velocity, normalised to the peak velocity, was derived at the time of peak pelvic velocity. Pearson's correlation coefficient was used to determine correlations. The normalised trunk rotation velocity at the peak pelvic velocity was significantly correlated with elbow valgus torque (R = -0.508, P = 0.032), shoulder external rotation torque (R = -0.507, P = 0.032) and ball speed (R = -0.504, P = 0.033). A smaller normalised trunk rotation angular velocity at the time of peak pelvic rotation velocity could increase ball speed but may also increase elbow and shoulder torques among pitchers who demonstrate trunk rotation after foot contact.

Relationship between ground reaction force and throwing arm kinetics in high school and collegiate pitchers

BACKGROUND

Throwing a baseball requires the transmission of forces generated in the lower extremity, through the trunk, to the upper extremity, and ultimately translates to the ball. A disruption in the functioning of the lower extremities could lead to altered upper extremity kinematics and increased load exerted on the shoulder and elbow. The purpose of this study was to examine the relationship of ground reaction forces (GRF) on the drive and stride sides and kinetics of the throwing arm in high school and collegiate baseball pitchers.

METHODS

In this retrospective cross-sectional study, data that were previously collected during a pitching evaluation were analyzed. Fifty high school pitchers and twenty six collegiate pitchers had received a pitching evaluation. Multiple regression analysis was used to examine the relationships between variables.

RESULTS

Only the drive leg medial force was determined to be a significant predictor of maximum shoulder external rotation torque. Maximum elbow valgus torque was not correlated with any GRF variables and ball speed was only weakly correlated with stride leg medial force. There were no significant differences in GRFs between the high school and college pitchers.

CONCLUSIONS

Due to the limited relationships present, other factors such as muscle strength, coordination, kinematics, or stride technique may overshadow the effects of GRF in highly skilled pitchers and warrant further investigation. Understanding this relationship will be important to both enhancing performance and avoiding injury.

Intra- versus inter-pitcher comparisons: Associations of ball velocity with throwing-arm kinetics in professional baseball pitchers

BACKGROUND

The association between ball velocity and elbow varus torque has shown differences when evaluated within a single pitcher and within a cohort. The impact of increasing ball velocity on additional throwing-arm kinetics, in particular shoulder distraction forces, with intra- vs. inter-pitcher evaluations has not been evaluated, even though these kinetic measures have been implicated in injury risk. The purpose of this study was to compare intra- vs. inter-pitcher relationships between ball velocity and all major kinetics at the shoulder and elbow in professional pitchers.

METHODS

A total of 323 professional baseball pitchers threw 8-12 fastball pitches while simultaneously being evaluated with 3-dimensional motion-capture technology (480 Hz). A linear regression analysis was performed to evaluate pitch velocity as a predictor of peak kinetic values at the shoulder and elbow among pitchers. A linear mixed model with random intercepts was then created to evaluate ball velocity as a predictor of peak kinetic values when comparing pitches within an individual pitcher.

RESULTS

91 pitchers were included in the analyses. Ball velocity among pitchers had weak correlations with shoulder distraction force (R² = 0.228, P < .001) and elbow distraction force (R² = 0.175, P < .001). Within an individual pitcher, strong correlations (R² > 0.85) were observed for (1) shoulder internal rotation torque (P < .001), (2) shoulder horizontal adduction torque (P = .006), (3) shoulder superior force (P < .001), (4) shoulder anterior force (P < .001), (5) elbow varus torque (P < .001), (6) elbow medial force (P < .001), (7) elbow anterior force (P < .001), (8) elbow flexion torque (P < .001), (9) shoulder distractive force (P < .001), and (10) elbow distractive force (P < .001).

CONCLUSION

Faster pitch velocity is a weak predictor of shoulder and elbow distraction forces experienced among professional pitchers. However, when controlling for an individual pitcher, peak kinetics at the shoulder and elbow can be strongly predicted by ball velocity. Therefore, the assumption that higher peak throwing-arm kinetic values are experienced by pitchers with faster ball velocity is likely an inappropriate assumption among pitchers but may be correct for each player who increases pitch velocity.

The association of stride length to ball velocity and elbow varus torque in professional pitchers

Professional basebal pitchers (n =315) were divided into quartiles based on increasing stride length and random intercept linear mixed-effect models were used to correlate stride length with ball velocity, pelvis and trunk rotation at foot contact, and throwing arm kinetics. Average stride length among all pitchers was 78.3±5.3%body height (%BH). For every 10% increase in stride length, ball velocity increased by 0.9 m/s (B =0.089, β =0.25, p <0.001) and trunk rotation initiation occurred 4.23 ms earlier (B =-0.42, β =-0.14, p <0.001). When divided into quartiles pelvis rotation was less towards home plate in Q1 compared to Q3 and Q4 (70.0±10.7° vs. 60.9±8.9° and 58.6±9.1°, p <0.001). No significant differences in shoulder internal rotation torque (p =0.173) or elbow varus torque (p =0.072) were noted between quartiles. Professional baseball pitchers who reached stride lengths of 80%BH or greater achieved faster ball velocity without an increase in elbow varus torque. This may, be a byproduct of rotating the pelvis for a greater proportion of the pitching motion and thereby more effectively utilising the lower extremities in the kinetic chain. Encouraging players to achieve this threshold of stride length may enhance ball velocity outcomes.

Comparative Pitching Biomechanics Among Adolescent Baseball Athletes: Are There Fundamental Differences Between Pitchers and Non-pitchers?

BACKGROUND

Approximately 25% of youth baseball players pitch, with most young athletes predominately playing multiple positions. While some youth baseball players may primarily pitch, other players may only pitch on occasion, potentially creating a pitching skill level discrepancy. Understanding potential kinematic and kinetic differences between pitching and non-pitching baseball players can inform injury risk reduction strategies for amateur athletes.

PURPOSE/HYPOTHESIS

To analyze differences in pitching biomechanics for fastballs, breaking balls, and change-ups in adolescent youth baseball players that identify as pitchers and non-pitchers.

STUDY DESIGN

Retrospective cross-sectional study.

METHODS

Baseball players were designated as pitchers or non-pitchers, who then threw fastballs (FB), breaking balls (BB), and change-ups (CH) during a biomechanical assessment. T-tests, Mann-Whitney U tests, and ANOVAs with Bonferroni correction, and effect sizes (ES) were performed.

RESULTS

Sixty baseball players (pitchers = 40; non-pitchers = 20; Age: 15.0 (1.1); Left-handed: 15%; Height 1.77 (0.09) m; Weight: 70.0 (12.5) kg) threw 495 pitches (FB: 177, BB: 155, CH: 163) for analysis. Pitchers threw 2 m/s faster and produced greater trunk rotation velocity (ES: 0.71 (95% CI: 0.39, 1.30, p<0.0001) than non-pitchers. Furthermore, pitchers demonstrated greater ground reaction force for FB compared to CH (ES: 0.48 (95% CI: 0.01, 0.94), p<0.0001). No other biomechanical differences were observed between pitchers and non-pitchers or between pitch types.

CONCLUSION

Despite throwing at greater velocity for all pitch types, baseball players that identify primarily as pitchers had overall similar kinematics and kinetics in comparison to baseball players that primarily identify as non-pitchers. Self-identified pitching baseball athletes have improved force transfer strategies for ball propulsion, utilizing different force production and attenuation strategies across different pitch types when compared to non-pitchers. Coaches should consider that novice pitchers may potentially have dissimilar trunk and ground reaction strategies in comparison to primary pitchers when designing appropriate pitch loading and recovery strategies.

LEVEL OF EVIDENCE

3.

The Evidence Behind Weighted Ball Throwing Programs for the Baseball Player: Do They Work and Are They Safe?

PURPOSE OF REVIEW

Weighted baseball throwing programs have gained significant attention recently. They have been promoted as proven option for pitchers wishing to increase their throwing velocity and improve throwing mechanics. However, there is some concern that, if not applied properly, they may increase injury risk. In this review, we aim to (1) give a brief description of the potential mechanisms through with weighed ball programs that could improve throwing velocity, (2) summarize the available evidence regarding their effectiveness in increasing throwing velocity, (3) summarize the evidence on injury risk, and (4) propose directions for future studies.

RECENT FINDINGS

Initial research on weighted ball programs was published in the 1960s. Recently there has been an increase in research as interest from baseball organizations, instructors, players, and medical providers has grown. A recent randomized controlled trial demonstrated that pitching velocity can be increased through a 6-week weighted ball program; however, with that, they found that the rate of injury also increased. An earlier systematic review outlined 10 studies that evaluated weighted ball programs effect on pitching velocity and reported that 7 studies described increases in throwing velocity, while most studies did not comment on injury risk. They note that the results on rate of injury have been variable, likely secondary to the variability in time and intensity of different programs. The inconsistency in the methodology of weighted ball programs and studies has made it challenging to draw (scientifically) meaningful conclusions. Nevertheless, several studies have offered empirical evidence in support of the claim that weighted ball programs can increase pitching velocity through improved throwing mechanics. At the same time, these studies have emphasized the improvements in performance, while the potential effects on injury mechanisms have been less well understood. There is a need for improved standardization of these programs to allow for future study and subsequent modification to optimize performance.

Effects of Mound Versus Flat-Ground Pitching and Distance on Arm Mechanics and Elbow Torque in High School Pitchers

Background:

Although the monitoring of a pitcher’s throwing arm workload has become a hot topic in both research and the pitching world, the impact of mound height and distance still remains unclear.

Purpose:

To compare the kinetics and kinematics between pitches from a mound and flat ground at 2 different distances.

Study Design:

Descriptive laboratory study.

Methods:

A total of 21 healthy high school varsity baseball pitchers (age, 16.2 ± 1.3 years; weight, 73.6 ± 11.0 kg; height, 181.3 ± 6.4 cm) participated in this study. Players were fitted with a motusBASEBALL sensor and sleeve. Each pitcher was instructed to pitch 5 fastballs under 4 conditions: mound at 60.5 ft (regulation distance), flat ground at 60.5 ft, mound at 50.5 ft, and flat ground at 50.5 ft. Linear mixed-effects models were used to account for both intra- and interplayer variability. A multivariable model was used to evaluate the association of mound pitching, flat-ground pitching, and their distances (50.5 ft and 60.5 ft), and their interaction to arm speed, arm slot, arm rotation, elbow varus torque, and ball velocity.

Results:

There were no statistically significant effects of mound, flat-ground, or distance variation on arm speed or shoulder rotation. Arm slot was significantly higher (+3.0°; P = .02) on pitches from the mound at 60.5 ft compared with 50.5 ft. Elbow varus torque was lower (–1.5 N·m; P = .02) on mound pitches at 60.5 ft compared with 50.5 ft. Pitches thrown from the mound displayed significantly faster ball velocity compared with flat-ground pitches at both distances (P < .01 for both), with pitches at 60.5 ft having higher velocity (+0.7 m/s; P < .01).

Conclusion:

Contrary to long-standing notions, the study results suggest that pitching from the mound does not significantly increase stress on the elbow compared with flat-ground pitching. Lower elbow varus torque and faster ball velocity at the regulation distance compared with the reduced distance indicate that elbow stress and ball velocity may not correlate perfectly, and radar guns may not be an appropriate surrogate measure of elbow varus torque.

Clinical Relevance:

A better understanding of the kinetic and kinematic implications of various throwing programs will allow for the designing of programs that are driven by objective data with aims directed toward injury prevention and rehabilitation in baseball pitchers.

The relationship between pitch velocity and shoulder distraction force and elbow valgus torque in collegiate and high school pitchers

BACKGROUND

The relationship between pitch velocity, shoulder distraction force, and elbow valgus torque is not well understood. The purpose of this study was to (1) determine the association between baseball pitch velocity and shoulder distraction force and (2) determine the association between baseball pitch velocity and elbow valgus torque. A subpurpose was to determine these same associations within subgroups of college baseball and high school baseball pitchers.

METHODS

Collegiate and high school baseball pitchers were biomechanically analyzed; variables extracted from the pitching reports included fastball pitch velocity, shoulder distraction force, and elbow valgus torque. Linear regression was performed to analyze the relationship between fastball velocity and shoulder and elbow kinetics. Subgroup analyses were then performed for college and high school pitches. Coefficients and 95% confidence intervals (95% CI) were calculated, with R squared (r²) used to assess model fit.

RESULTS

A total of 70 pitchers (college: n = 23; high school: n = 47) were included in this study. There was a positive weak linear relationship between pitch velocity and shoulder distraction force (3.24 %body weight [BW] [95% CI: 2.07, 4.40], r² = 0.32, P < .001) and elbow valgus torque (0.16 %body weight × height [BW × H] [95% CI: 0.11, 0.20], r² = 0.44, P < .001). College pitchers did not exhibit a relationship between pitch velocity and shoulder distraction force (1.44 %BW [95% CI: -2.50, 5.38], r² = 0.02, P < .001), whereas high school pitchers did exhibit a weak positive linear relationship between pitch velocity and shoulder distraction force (3.69 %BW [95% CI: 2.25, 5.14], r² = 0.36, P < .001). Both college and high school pitchers exhibited a weak positive relationship between pitch velocity and elbow valgus torque (college: 0.15 %BW × H [95% CI: 0.05, 0.25], r² = 0.29, P < .001; high school: 0.16 %BW × H [95% CI: 0.09, 0.22], r² = 0.36, P < .001).

DISCUSSION

Pitching velocity exhibited a weak positive linear relationship with both shoulder distraction force and elbow valgus torque. However, only high school pitchers were observed to have a weak positive linear relationship between pitch velocity and shoulder distraction force, whereas both college and high school pitchers exhibited a weak positive relationship between pitch velocity and elbow valgus torque. These findings suggest that older pitchers may attenuate shoulder forces with increased pitch velocity due to physical maturity or increased pitching mechanical skill in comparison with younger pitchers.

Changes in Muscle Activity among College Pitchers Using 5- to 12-Oz Weighted Baseball

OBJECTIVES Several studies have reported that weighted baseball (WB) training is effective in improving ball speed; however, the weight of the ball suitable for training remains unclear. This study aimed to investigate the changes in muscle activity during pitching using 5- to12-oz WBs and to provide basic data for training programs to improve pitching speed.METHODS The subjects of this study were 10 overhand pitchers who had more than 5 years of experience. Muscle activity was measured and analyzed at 70–85% of throwing baseball maximum effort (TBME) during soft toss (ST) and TBME was evaluated using electromyography.RESULTS As the ball weight increased, muscle activity also increased in all pitching phases. Muscle activity was higher during ST with WBs heavier than 10 or 11oz than during TBME, indicating that the loads on the shoulder and elbow joint muscles increased. Conversely, muscle activity during ST with 5- to 7-oz WBs was lower than that during TBME, although phase and muscle group differences were observed.CONCLUSIONS The results of this study suggest that training with 8- to 10-oz WBs could increase muscle strength and activity, although the effect may vary with fitness level and muscle strength.

Predictors of elbow torque among professional baseball pitchers

BACKGROUND

Overuse injuries of the shoulder and elbow continue to be prevalent in elite baseball pitchers. Pitch velocity has been shown to impact medial elbow torque in adolescent baseball pitchers. However, the determinants of medial elbow torque in professional baseball pitchers are not known.

PURPOSE

To determine the influence of pitch type, velocity, and player characteristics on medial elbow torque in professional baseball pitchers.

METHODS

Professional baseball pitchers were recruited for participation. Height, weight, body mass index (BMI), and throwing arm measurements were obtained for all study participants. While wearing a gyroscopic sensor equipped with an accelerometer, participants were instructed to throw a standard, randomized sequence of fastballs, changeups, and curveballs. Elbow torque, arm slot, arm speed, shoulder rotation, and ball velocity were recorded for each pitch. A linear mixed model was used to evaluate the association of pitch type with each pitch parameter, adjusting for pitchers' demographics.

RESULTS

A total of 12 professional baseball pitchers were included in this study. Among the pitch types, medial elbow torque was significantly higher in fastballs than in curveballs (P = .001). An increased BMI value was independently associated with decreased elbow torque in pitchers (P = .035).

CONCLUSION

Fastballs place significantly higher torque on the medial elbow than do curveballs, which is consistent with previous studies done on high school and collegiate populations. Pitchers with a higher BMI experience significantly less torque across the medial elbow.

Impact of shoe and cleat type on youth baseball pitching biomechanics

Shoulder and elbow injuries among baseball pitchers of various ages and abilities continue to rise despite exhaustive efforts analysing pitch type and count; however, it has yet been determined if footwear plays a role in altering pitching mechanics and subsequently injury susceptibility. Therefore, the purpose of the study was to investigate the effect footwear might have on youth baseball pitching mechanics. Data were collected on eleven youth baseball pitchers wearing two different shoes on two different surface inclinations. A repeated measures ANOVA was utilised to determine differences between upper and lower extremity joint kinematics and kinetics (p < 0.05). Results indicate wearing moulded cleats elicited significantly greater amounts of shoulder internal rotation torque, angle and velocity as well as elbow varus torque. Turf shoes caused an increased plantarflexion joint angle in the stride leg ankle and shoulder external rotation torque, angle and velocity. The findings of this study suggest that the footwear worn by a youth baseball pitcher does alter the shoulder and elbow dynamics in the dominant throwing arm as well as the amount of ankle plantarflexion in the stride leg.

Glenohumeral external rotation weakness partially accounts for increased humeral rotation torque in youth baseball pitchers

OBJECTIVES

To examine differences in shoulder internal rotation (IR) torque among youth pitchers of above and below average relative glenohumeral (GH) rotation strength levels. It was hypothesized that differences in IR torque during the pitching motion would could be explained by differences in relative IR and external rotation (ER) strength.

DESIGN

Descriptive laboratory study.

METHODS

Isometric GH rotation strength and upper extremity pitching mechanics were assessed in 78 male youth baseball pitchers (12.7±2.0yrs; 1.63±14.0m; 56.9±12.4kg). Shoulder IR torque during the pitch was examined at maximum humeral external rotation (MER) and throughout the arm acceleration phase (ACC). Multivariate analysis of covariance (MANCOVA) was used to examine the differences in pitching IR torque between GH strength groups.

RESULTS

A significant main effect of ER strength on the dependent variables was present after controlling for fastball velocity (λ=0.855, F_2,72=6.13, p=0.003, η_p²=0.145). Follow up univariate tests indicated significant differences in IR torque between strength groups at MER (F_1,73=12.36, p<0.001, η_p²=0.145) and during ACC (F_1,73=6.65, p= 0.012, η_p²=0.083). Participants who displayed ER strength at or below the group mean experienced greater IR torque at MER and greater average IR torque during ACC than participants who displayed ER strength above the group mean.

CONCLUSIONS

Weakness of the GH ER musculature partially accounts for increased shoulder IR torque during pitching.

Differences in PlayerLoad and pitch type in collegiate baseball players

PlayerLoad is derived from a tri-axial accelerometer device and is a measure of an athlete's external training load. Tri-axial accelerometers (Optimeye S5, Catapult Sports, Melbourne, Australia) were worn by 25 collegiate pitchers during a pitching session. Pitches included fastballs, curve balls, sliders, and changeups. Peak and sum PlayerLoad were calculated for fastballs, curve balls, sliders, and changeups. Statistical analysis included paired t-tests (p < 0.01) and effect size indexes (ESI). Peak and sum PlayerLoad were higher for fastballs compared to changeups (N = 20; ESI_peak = 0.47, p= 0.001 and ESI_Sum = 0.13, p = 0.001, respectively). Peak and sum PlayerLoad were not different comparing fastball to curveball (N = 12; ESI_peak = 0.24, p = 0.050 and ESI_Sum<0.01, p = 0.106) and fastball to slider (N = 12; ESI_peak = 0.32, p = 0.088 and ESI_Sum = 0.02, p = 0.221). Fastball velocity (37.1 ± 2.1 m/s) differed from the changeup (33.8 ± 1.9 m/s; p < 0.001), curveball (32.2 ± 1.2; p < 0.001), and slider (33.8 ± 1.3 m/s; p < 0.001). Pitching workload may differ based on pitch type. Pitch counts may not capture true player fatigue due to variability in stresses resulting from different pitch types.

Segmental Power Analysis of Sequential Body Motion and Elbow Valgus Loading During Baseball Pitching: Comparison Between Professional and High School Baseball Players

Background:

Pitching-related elbow injuries remain prevalent across all levels of baseball. Elbow valgus torque has been identified as a modifiable risk factor of injuries to the ulnar collateral ligament in skeletally mature pitchers.

Purpose:

To examine how segmental energy flow (power) influences elbow valgus torque and ball speed in professional versus high school baseball pitchers.

Study Design:

Descriptive laboratory study.

Methods:

A total of 16 professional pitchers (mean age, 21.9 ± 3.6 years) and 15 high school pitchers (mean age, 15.5 ± 1.1 years) participated in marker-based motion analysis of baseball pitching. Ball speed, maximum elbow valgus torque (MEV), temporal parameters, and mechanical power of the trunk, upper arm, and forearm were collected and compared using parametric statistical methods.

Results:

Professional pitchers threw with a higher ball speed (36.3 ± 2.9 m/s) compared with high school pitchers (30.4 ± 3.5 m/s) (P = .001), and MEV was greater in professional pitchers (71.3 ± 20.0 N·m) than in high school pitchers (50.7 ± 14.6 N·m) (P = .003). No significant difference in normalized MEV was found between groups (P = .497). Trunk rotation time, trunk power, and upper arm power combined to predict MEV (r = 0.823, P < .001), while trunk rotation time and trunk power were the only predictors of ball speed (r = 0.731, P < .001). There were significant differences between the professional and high school groups in the timing of maximum pelvis rotation velocity (42.9 ± 9.7% of the pitching cycle [%PC] vs 27.9 ± 23.4 %PC, respectively; P < .025), maximum trunk rotation (33 ± 16 %PC vs 2 ± 23 %PC, respectively; P = .001), and maximum shoulder internal rotation velocity (102.4 ± 8.9 %PC vs 93.0 ± 11.7 %PC, respectively; P = .017).

Conclusion:

The power of trunk motion plays a critical role in the development of elbow valgus torque and ball speed. Professional and high school pitchers do not differ in elbow torque relative to their respective size but appear to adopt different patterns of segmental motion.

Clinical Relevance:

Because trunk rotation supplies the power associated with MEV and ball speed, training methods aimed at core stabilization and flexibility may benefit professional and high school pitchers in reducing the injury risk and improving pitching performance.

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.

Changes in Throwing Arm Mechanics at Increased Throwing Distances During Structured Long-Toss

BACKGROUND

Elbow injuries among adolescent baseball players have been outpacing those of college and professional players. In attempts to prevent injuries and maximize return-to-play potential following injury, attention has been focused on "return to throw" programs, which include long-toss throws. Because the few studies that were conducted on long-toss throwing focused primarily on college-aged athletes, it is not known what type of load is incurred at the elbow during interval throwing progression among high school baseball players.

PURPOSE

To quantify the change in arm slot, arm speed, shoulder external rotation, and elbow varus torque across increasing throwing distances within a given athlete.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Ninety-five high school baseball players performed a long-toss protocol while wearing an inertial sensor and sleeve. Each participant was tested for 5 throws at distances of 9 m, 18 m, 27 m, 37 m, and 46 m. Linear mixed-effects models and likelihood ratio tests were used to estimate the within-participant relationship between throw distance and arm slot, arm speed, shoulder external rotation, and elbow varus torque.

RESULTS

Arm slot ( P < .01), arm speed ( P < .01), shoulder external rotation ( P < .01), and elbow varus torque ( P < .01) were significantly associated with long-toss throw distance. As the throw distance increased, there was an increase in arm speed and shoulder external rotation and a decrease in arm slot for each distance. However, elbow varus torque increased with each distance up to 37 m and then remained the same at 46 m.

CONCLUSION

The use of longer distances for conditioning and rehabilitation may be beneficial in increasing shoulder range of motion and arm speed; however, precaution needs to be taken, as throwing longer distances are accompanied by an increase in arm rotation, arm speed, and elbow torque, with a decrease in arm slot.

CLINICAL RELEVANCE

Return-to-throw programs have been utilized by sports medicine clinicians and coaches to help guide a player during rehabilitation. These programs involve throwing at increased efforts through increased distances with no immediate feedback on elbow stress. This investigation describes arm biomechanical changes during submaximum interval throwing and demonstrates a tool that can be utilized to measure arm stress in real time for clinicians and athletes progressing through an interval throwing program.

Predictors of Elbow Torque Among Youth and Adolescent Baseball Pitchers

BACKGROUND

There has been an increasing incidence of overuse elbow injuries among youth and adolescent pitchers. Pitch type has been implicated as a risk factor for excess torque at the medial elbow; however, this has not been definitively demonstrated.

PURPOSE

To assess predictors of torque across the medial elbow in youth and adolescent pitchers with a mobile sensor. In addition, the authors aimed to determine the differences in elbow torque produced according to pitch type (fastball, curveball, changeup) and pitcher demographics.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Twenty youth and adolescent pitchers were instructed to throw 8 fastballs, 8 curveballs, and 8 changeups in a standardized but randomized sequence over a 25-minute period. Five pitchers were evaluated each day. A sensor placed at the medial elbow reported elbow torque, arm speed, arm slot, and shoulder rotation for each pitch, while a radar gun measured peak ball velocity. The primary outcome was a determination of thrower and pitch characteristics associated with elevated torque across the medial elbow. Secondary outcomes included the evaluation of differences in throwing biomechanics among different pitch types. Outcomes were assessed via a multivariable model, which controlled for possible covariates.

RESULTS

In total, 20 youth baseball pitchers with a mean age of 14.1 years (range, 12-17 years) were included in the study. On average, fastballs caused the greatest torque across the medial elbow (least squares mean ± SE, 47.3 ± 0.5 N·m) as compared with changeups (44.2 ± 0.5 N·m; P < .001) and curveballs (45.0 ± 0.5 N·m; P = .002). However, curveballs produced the greatest arm speed (917.8 rpm). Pitchers who started throwing curveballs at an older age experienced less elbow torque ( P < .001). A multivariable model demonstrated that increased ball velocity and body mass index and decreased arm slot were independent predictors of increased elbow torque. Conversely, increasing age, longer arm length, and greater elbow circumference were independent protectors against elbow torque.

CONCLUSION

This study found that among youth and adolescent pitchers, fastballs generate the highest elbow torque while curveballs generated the greatest arm speed. Increased ball velocity and body mass index and decreased arm slot were predictors of elbow torque; however, increasing age and size of a pitcher's arm were protectors against elbow torque. These findings are important to better understand risk factors for overuse injury in this at-risk athletic population.

CLINICAL RELEVANCE

These findings may inform future pitching recommendations with intentions of curtailing medial elbow injuries experienced by young pitchers, such as ulnar collateral ligament injuries.

Effect of a 6-Week Weighted Baseball Throwing Program on Pitch Velocity, Pitching Arm Biomechanics, Passive Range of Motion, and Injury Rates

BACKGROUND

Emphasis on enhancing baseball pitch velocity has become popular, especially through weighted-ball throwing. However, little is known about the physical effects or safety of these programs. The purpose of this study was to examine the effects of training with weighted baseballs on pitch velocity, passive range of motion (PROM), muscle strength, elbow torque, and injury rates.

HYPOTHESIS

A 6-week weighted ball training program would result in a change in pitching biomechanical and physical characteristics.

STUDY DESIGN

Randomized controlled trial.

LEVEL OF EVIDENCE

Level 1.

METHODS

During the baseball offseason, 38 healthy baseball pitchers were randomized into a control group and an experimental group. Pitch velocity, shoulder and elbow PROM, shoulder strength, elbow varus torque, and shoulder internal rotation velocity were measured in both groups. The experimental group then performed a 6-week weighted ball throwing program 3 times per week using balls ranging from 2 to 32 ounces while the control group only used a 5-ounce regulation baseball. Both groups performed a strength training program. Measurements were then repeated after the 6-week period. Injuries were tracked over the 6-week training program and the subsequent baseball season. The effect of training with a weighted ball program was assessed using 2-way repeated-measures analysis of variance at an a priori significance level of P < 0.05.

RESULTS

Mean age, height, mass, and pretesting throwing velocity were 15.3 ± 1.2 years (range, 13-18 years), 1.73 ± 0.28 m, 68.3 ± 11 kg, and 30.3 ± 0.7 m/s, respectively. Pitch velocity showed a statistically significant increase (3.3%) in the experimental group ( P < 0.001). There was a statistically significant increase of 4.3° of shoulder external rotation in the experimental group. The overall injury rate was 24% in the experimental group. Four participants in the experimental group suffered elbow injuries, 2 during the training program and 2 in the season after training. No pitchers in the control group were injured at any time during the study.

CONCLUSION

Performing a 6-week weighted ball throwing program increased pitch velocity. However, the program resulted in increased shoulder external rotation PROM and increased injury rate.

CLINICAL RELEVANCE

Although weighted-ball training may increase pitch velocity, caution is warranted because of the notable increase in injuries and physical changes observed in this cohort.

Role of Rotational Kinematics in Minimizing Elbow Varus Torques for Professional Versus High School Pitchers

Background:

Elbow injury rates among baseball pitchers are rapidly rising. However, this increase has been most dramatic among high school (HS) pitchers.

Purpose:

To examine pitch velocity and the kinetic and kinematic characteristics of HS versus professional (PRO) pitchers to identify potential differences that may play a role in the increased risk of ulnar collateral ligament injury in youth pitchers.

Study Design:

Controlled laboratory study.

Methods:

A total of 37 HS (mean ± SD: age, 16 ± 1 years) and 40 PRO (age, 21 ± 2 years) baseball pitchers completed maximal-effort baseball pitches during a single testing session, from which pitch velocity (PV), absolute and normalized elbow varus torque (EVT_A and EVT_N, respectively) during arm cocking and at maximum shoulder external rotation (MER), and 8 other elbow and shoulder torques or forces and rotational kinematics of the pelvis and trunk were analyzed, recorded, and compared.

Results:

PV was greater in PRO than HS athletes; EVT_A was greater in PRO than HS athletes during arm cocking and at MER; but EVT_N was similar during arm cocking and greater in HS than PRO athletes at MER. In PRO athletes, PV was not related to EVT_A during arm cocking or MER (r = 0.01-0.05). Furthermore, in PRO athletes, EVT_A during arm cocking and at MER were inversely related to upper trunk rotation at hand separation and foot contact and to pelvis rotation at elbow extension (r = –0.30 to –0.33). In contrast, in HS athletes, PV was strongly related to EVT_A during arm cocking and MER (r = 0.76-0.77). Furthermore, in HS athletes, PV and EVT_A during arm cocking and at MER were moderately or strongly related to the other elbow and shoulder torques and forces (r = 0.424-0.991), and EVT_A was not related to upper trunk rotation or pelvis rotation throughout the throwing motion (r = –0.16 to 0.15).

Conclusion:

The kinetic and rotational kinematic differences observed between PRO and HS pitchers in this study may help explain the greater performance of PRO pitchers while allowing them to minimize EVT during pitching. HS pitchers, however, do not appear to be as capable of utilizing the forces generated by rotation of their trunk and pelvis to aid in pitching, and those who throw the hardest generate the greatest forces at the shoulder and elbow. As a result, they experience higher EVTs relative to their body size, which may place them at an increased risk of injury.

Clinical Relevance:

HS pitchers throw harder primarily by generating larger forces in the arm and shoulder. Thus, owing to the relative physical immaturity of HS versus PRO pitchers, these factors may place them at an increased risk of injury. Coaches may first wish to focus on improving the rotational kinematics of HS pitchers rather than first focusing on achieving greater pitch velocities.

The Impact of Workload on the Evolution of Hip Internal and External Rotation in Professional Baseball Players Over the Course of the Season

Background

Although restricted hip range of motion (ROM) is associated with an increased risk for injuries in baseball players, the evolution of hip ROM over the season remains undefined.

Hypothesis

Hip ROM profiles would be symmetric between hips and positions (pitchers vs position players) but would decrease from preseason to postseason. Additionally, it was hypothesized that this decrease in motion would correlate with workload.

Study Design

Cohort study; Level of evidence, 2.

Methods

Bilateral hip ROM was assessed in 96 professional baseball players (54 pitchers, 42 position players) preseason and postseason. ROM comparisons were made between lead and trailing hips, pitchers and position players, and preseason and postseason measures. The change from preseason to postseason was correlated with player demographics and measures of workload for pitchers and position players.

Results

Preseason hip ROM was symmetric between hips; however, pitchers demonstrated increased preseason lead hip internal rotation (IR) (P = .018) and bilateral hip total ROM (TROM) (P < .020) compared with position players. From preseason to postseason, position players lost 7° of external rotation (ER) (P ≤ .005 ). In pitchers, the loss of IR correlated with increased pitches (P = .016) and innings (P = .037), while the loss of ER (P = .005 ) and TROM (P = .014) correlated with increasing mean fastball velocity. Workload for position players did not correlate with motion loss.

Conclusion

Symmetric hip ROM profiles should be anticipated in baseball players; however, pitchers may have increased preseason IR and TROM and postseason ER and TROM relative to position players. Although loss of motion correlated with workload in pitchers, this was not the case for position players. Hip motion should be monitored over the course of the season. This is particularly true for pitchers who lose IR as workload increases, which may place them at a greater risk for injuries.

The Relationship of Throwing Arm Mechanics and Elbow Varus Torque: Within-Subject Variation for Professional Baseball Pitchers Across 82,000 Throws

BACKGROUND

Likely due to the high level of strain exerted across the elbow during the throwing motion, elbow injuries are on the rise in baseball. To identify at-risk athletes and guide postinjury return-to-throw programs, a better understanding of the variables that influence elbow varus torque is desired.

PURPOSE

To describe the within-subject relationship between elbow varus torque and arm slot and arm rotation in professional baseball pitchers.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A total of 81 professional pitchers performed 82,000 throws while wearing a motusBASEBALL sensor and sleeve. These throws represented a combination of throw types, such as warm-up/catch, structured long-toss, bullpen throwing from a mound, and live game activity. Variables recorded for each throw included arm slot (angle of the forearm relative to the ground at ball release), arm speed (maximal rotational velocity of the forearm), arm rotation (maximal external rotation of the throwing arm relative to the ground), and elbow varus torque. Linear mixed-effects models and likelihood ratio tests were used to estimate the relationship between elbow varus torque and arm slot, arm speed, and arm rotation within individual pitchers.

RESULTS

All 3 metrics-arm slot (χ² = 428, P < .001), arm speed (χ² = 57,683, P < .001), and arm rotation (χ² = 1392, P < .001)-were found to have a significant relationship with elbow varus torque. Within individual athletes, a 1-N.m increase in elbow varus torque was associated with a 13° decrease in arm slot, a 116 deg/s increase in arm speed, and an 8° increase in arm rotation.

CONCLUSION

Elbow varus torque increased significantly as pitchers increased their arm rotation during the arm cocking phase, increased the rotational velocity of their arm during the arm acceleration phase of throwing, and decreased arm slot at ball release. Thus, shoulder flexibility, arm speed, and elbow varus torque (and likely injury risk) are interrelated and should be considered collectively when treating pitchers.

CLINICAL RELEVANCE

It is well established that elbow varus torque is related to ulnar collateral ligament injuries in overhead throwers. This study describes the relationship of arm slot, arm speed, and arm rotation to elbow varus torque in an attempt to identify modifiable risk factors for injury.

Elbow MRI Findings Do Not Correlate With Future Placement on the Disabled List in Asymptomatic Professional Baseball Pitchers

BACKGROUND

Injury rates among professional baseball players may reach as high as 5.8 per 1000 encounters, with pitchers being most vulnerable on account of the excessive biomechanical load on the upper extremity during the throwing motion. Anatomically, the shoulder is the most common site of pitching-related injury, accounting for 30.7% of injuries, closely followed by the elbow at 26.3%. Characteristic valgus loading imparts a predictable constellation of stresses on the joint, including medial tension, lateral compression, and posterior medial shearing. The degenerative cohort of tissue changes that result are readily detected on magnetic resonance imaging (MRI). It is not yet known whether such findings predict future placement on the disabled list (DL) in asymptomatic Major League pitchers.

HYPOTHESIS

Abnormal soft tissue and osseous changes detected on MRI of the throwing elbow in asymptomatic professional pitchers will impart an increased risk of subsequent transfer to the DL in the season after MRI.

STUDY DESIGN

Retrospective cohort study.

LEVEL OF EVIDENCE

Level 3.

METHODS

The study aimed to examine a potential association between the total number of innings pitched (approximate lifetime valgus load) and the typical MRI degenerative changes, hypothesizing a rejection of the null hypothesis. A total of 26 asymptomatic professional pitchers from a single Major League Baseball (MLB) organization and its various minor league affiliates underwent MRI of their dominant elbow from 2003 to 2013 as a condition of their contract signing or trade. Twenty-one of those pitchers played at the Major League level while 5 played with the team's minor league affiliates including both the AA and AAA levels. Asymptomatic was defined as no related stints on the DL due to elbow injury in the 2 seasons prior to MRI. A fellowship-trained musculoskeletal radiologist reevaluated the studies after being blinded to patient name, injury history, and baseball history. A second investigator collected demographic data; this included total career number of innings pitched and any subsequent DL reports for each subject while remaining blinded to the MRI results.

RESULTS

The mean age at the time of MRI was 29.6 years (range, 19-39 years). The mean number of innings pitched was 1111.7. Of the 26 pitchers, 13 had scar remodeling of the anterior bundle of the ulnar collateral ligament (UCL). Of those, 4 had partial-thickness tears of the anterior bundle of the UCL, ranging from 10% to 90% of the total thickness. Twelve had articular cartilage loss within the posteromedial margin of the ulnohumeral joint, and 12 had posteromedial olecranon marginal osteophytes. Seven pitchers had degeneration of the common extensor tendon origin, 10 had degeneration of the flexor pronator mass, 9 had insertional triceps tendinosis, 2 had enthesopathic spurs at the sublime tubercle, 3 had osteochondral intra-articular bodies, and 2 subjects had joint effusions. In the year after MRI, 6 pitchers were placed on the DL for elbow-related injuries. There was no robust correlation between any single MRI finding and subsequent transfer to the DL, and no statistically significant correlation between number of innings pitched and MRI findings, although some trends were observed for both.

CONCLUSION

MRI findings in asymptomatic MLB pitchers were not associated with placement on the DL within the subsequent year. While a trend was observed with olecranon osteophytes and subsequent DL placement ( P = 0.07), this finding did not reach statistical significance. Furthermore, there was no robust correlation between the number of innings pitched with the presence of any of the aforementioned degenerative changes on MRI.

CLINICAL RELEVANCE

The characteristic structural transformation that occurs in the throwing elbow of professional pitchers is predictable and readily detectable on MRI. However, this study suggests that these changes are not predictive of near-term placement on the DL in those who are asymptomatic. Abnormal findings on MRI, even high-grade partial UCL tears, do not correlate with near-term placement on the DL, mitigating their potential negative impact on signing decisions.

Optimal management of ulnar collateral ligament injury in baseball pitchers

The ulnar collateral ligament stabilizes the elbow joint from valgus stress associated with the throwing motion. During baseball pitching, this ligament is subjected to tremendous stress and injury if the force on the ulnar collateral ligament during pitching exceeds the physiological limits of the ligament. Injuries to the throwing elbow in baseball pitchers result in significant time loss and typically surgical intervention. The purpose of this paper is to provide a review of current information to sports medicine clinicians on injury epidemiology, injury mechanics, injury risk factors, injury prevention, surgical interventions, nonsurgical interventions, rehabilitation, and return to play outcomes in baseball pitchers of all levels.

Correlation of Shoulder and Elbow Kinetics With Ball Velocity in Collegiate Baseball Pitchers

CONTEXT

Throwing a baseball is a dynamic and violent act that places large magnitudes of stress on the shoulder and elbow. Specific injuries at the elbow and glenohumeral joints have been linked to several kinetic variables throughout the throwing motion. However, very little research has directly examined the relationship between these kinetic variables and ball velocity.

OBJECTIVE

To examine the correlation of peak ball velocity with elbow-valgus torque, shoulder external-rotation torque, and shoulder-distraction force in a group of collegiate baseball pitchers.

DESIGN

Cross-sectional study.

SETTING

Motion-analysis laboratory.

PATIENTS OR OTHER PARTICIPANTS

Sixty-seven asymptomatic National Collegiate Athletic Association Division I baseball pitchers (age = 19.5 ± 1.2 years, height = 186.2 ± 5.7 cm, mass = 86.7 ± 7.0 kg; 48 right handed, 19 left handed).

MAIN OUTCOME MEASURE(S)

We measured peak ball velocity using a radar gun and shoulder and elbow kinetics of the throwing arm using 8 electronically synchronized, high-speed digital cameras. We placed 26 reflective markers on anatomical landmarks of each participant to track 3-dimensional coordinate data. The average data from the 3 highest-velocity fastballs thrown for strikes were used for data analysis. We calculated a Pearson correlation coefficient to determine the associations between ball velocity and peak elbow-valgus torque, shoulder-distraction force, and shoulder external-rotation torque (P < .05).

RESULTS

A weak positive correlation was found between ball velocity and shoulder-distraction force (r = 0.257; 95% confidence interval [CI] = 0.02, 0.47; r(2) = 0.066; P = .018). However, no significant correlations were noted between ball velocity and elbow-valgus torque (r = 0.199; 95% CI = -0.043, 0.419; r(2) = 0.040; P = .053) or shoulder external-rotation torque (r = 0.097; 95% CI = -0.147, 0.329; r(2) = 0.009; P = .217).

CONCLUSIONS

Although a weak positive correlation was present between ball velocity and shoulder-distraction force, no significant association was seen between ball velocity and elbow-valgus torque or shoulder external-rotation torque. Therefore, other factors, such as improper pitching mechanics, may contribute more to increases in joint kinetics than peak ball velocity.

A speed distance-based classification system for injury prevention and research in international and domestic youth baseball players

BACKGROUND

An objective classification system for studying youth baseball players in the U.S.A. was published in 1996. Professional baseball is composed of greater than 25% international players a majority of whom come from five countries. Many youth baseball players are injured in early years play, both in the U.S.A. and internationally. There is no international classification system to study youth baseball pitching injuries, biomechanics, or maturation, but one is needed in order to compare and combine pitchers in multi-center studies. Uniform domestic and international pre-injury normative data is optimum. Ideally, data collection should be practical requiring inexpensive equipment and limited time demands.

HYPOTHESIS

The mathematical model, developed in 1996 on 853 boys and validated on 114 boys in the Mid-Atlantic Region, U.S.A., is internationally applicable, allowing easy classification of youth baseball pitchers and levels throughout the world.

METHODS

Seven-hundred-twenty-one international pitchers, ages 8-14, threw five full-speed pitches recorded with a calibrated radar gun and four maximum distance throws on a marked field. Demographics included age, height, weight, and years pitched. Collection sites included foreign national baseball clubs (Dominican Republic, Venezuela, Puerto Rico, Japan and the Philippines), the Mexican national youth tournament, and a multinational tournament (Brazil, Peru and Colombia). The mathematical model developed in 1996 was used to generate predicted distances for this sample for comparison with actual distances. In addition to the overall analysis, adequate sample sizes were available for comparing predicted and actual distances by country for four of the countries.

RESULTS

The correlation between predicted distance using the mathematical model and actual distance was 0.90. The mean of the international players was 1-2 standard deviations above the USA mean for speed and one standard deviation above the mean for distance. There was no systematic over or under prediction indicating that both relative and absolute fit for the model was excellent.

CONCLUSIONS

The mathematical model developed in 1996 on U.S.A. baseball players is robustly generalizable to international youth baseball pitchers.

CLINICAL RELEVANCE

Pre-injury distance/speed data allows for classification of youth baseball player of multiple levels between the ages of 8-14. International and regional comparisons are now possible for multi-center studies in order to better define risk factors, compare studies, and combine data based upon pre-injury maximum long toss data. Data collection requires only a field, a few balls, and a tape measure.