Correlation of torque and elbow injury in professional baseball pitchers

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.

The ulnar collateral ligament response to valgus stress, repetitive pitching, and elbow muscle contraction in asymptomatic baseball pitchers

Background

In baseball, repetitive pitching leads to medial elbow injuries, particularly to the ulnar collateral ligament (UCL). To prevent pitchers from UCL injuries, it is important to quantify the response to elbow stress. Repetitive elbow external valgus torque and muscular fatigue induced by repetitive pitching could affect markers of the response, that is, humeroulnar joint gap and UCL morphology. The aims of the study were three-folded: to investigate the effect of (1) exerted handgrip force on the humeroulnar joint gap, (2) repetitive pitching on the humeroulnar joint gap and the UCL morphology, and (3) exerted handgrip force on the humeroulnar joint gap for different levels of elbow valgus stress is different after compared to before repetitive pitching in asymptomatic baseball pitchers.

Methods

Medial elbow ultrasound images were collected in 15 asymptomatic male baseball pitchers. Three levels of static elbow valgus stress (0N, 50N, 100N) were applied with a TELOS device before and after repetitive pitching and with or without handgrip force. These images were used to assess the humeroulnar joint gap size and UCL length and thickness. After 110 fastball pitches or when 80% self-perceived fatigue on a VAS scale was reached, participants were instructed to stop throwing. Repeated measures ANOVAs were used to statistically test significant differences.

Results

Handgrip force did not significantly affect the humeroulnar joint gap. The UCL thickness and length and the humeroulnar joint gap were also not different after compared to before repetitive pitching. While higher levels of applied valgus stress significantly increased the humeroulnar joint gap (P < .001), this effect was not significantly different in the interaction with handgrip force and repetitive pitching.

Conclusion

The humeroulnar joint gap changes for different levels of elbow valgus stress. However, adult baseball pitchers did not respond to elbow stress after a single pitching session with or without submaximal handgrip force in the humeroulnar joint gap and UCL morphology.

Elbow valgus stress during towel drills in college baseball players

BACKGROUND

In baseball players with elbow injuries, towel drills are clinically used before initiating active throwing exercises to gradually increase stress across the elbow. However, elbow valgus torque during towel drills remains unknown. Moreover, towel drills and active ball throws might have different relationships between biomechanical metrics, such as elbow stress, arm slot, and arm speed. Therefore, the aims of this study were 1) to demonstrate the difference in elbow valgus stress between towel drills and active ball throws and 2) to evaluate the correlation between elbow valgus torque and other biomechanical metrics including arm slot and arm speed in towel drills and active ball throws.

METHODS

Seventeen healthy college baseball players performed three towel drills using a face towel, short foam tube, and long foam tube, followed by full-effort throwing on flat ground. Each participant completed five consecutive trials of each task, and the elbow valgus torque, arm slot, and arm speed were measured using wearable sensors. One-way repeated analysis of variance and post-hoc tests were used to determine the differences in biomechanical metrics among the tasks. Furthermore, the correlation between the elbow valgus torque and other metrics was evaluated using Pearson correlation coefficients.

RESULTS

Elbow valgus torque was lower in towel drills compared to that of active ball throws; however, the stress during towel drills using a face towel reached almost 80% of the maximum effort of active ball throws. There was no relationship between elbow valgus stress and arm slot in either the towel or active ball throw tasks. However, a higher arm speed was associated with greater elbow valgus torque in towel drills, whereas no relationship between elbow stress and arm speed was found in active ball throws.

CONCLUSION

Precaution must be taken in athletes following a progressive throwing program because elbow valgus stress reaches almost 80% of the full-effort throw, even when using a face towel in a towel drill. Hence, the subjective intensity must be controlled even in towel drills to gradually increase the medial elbow stress. Moreover, the mechanisms underlying changes in elbow stress may differ between towel drills and active ball throws. Future investigations on the difference between towel drills and active ball throws may help understand the underlying mechanism of alterations in elbow valgus torque during the throwing movement.

Current concepts: pathology in the overhead athlete's lateral elbow

The lateral elbow is subjected to increasing compressive force in response to repetitive valgus stress. Alterations or deficiencies in overhead mechanics and the kinetic chain may predispose an athlete to injury. Evaluation includes a focused elbow physical examination and imaging, supplemented by a robust screening of core strength, balance, and mechanics of the kinetic chain. Treatment of osteochondritis dissecans, a common lateral elbow pathology, varies based on stability of the lesion, with variable, but often positive outcomes. Proper pitching mechanics, kinetic chain integrity, and workload management provide potential opportunities for prevention.

Assessing Biomechanical and Clinical Outcomes of an Elbow Orthosis Intervention in Youth Baseball: Preliminary Results

Proper orthosis design may help youth baseball players develop safer pitching mechanics to prevent elbow injuries. This study evaluated the impact of a custom elbow orthosis on pitching biomechanics and adverse events. Ten 11-12-year-old players (mean age 11.5 years) from a regional league team were recruited. The inclusion criteria were at least two years of baseball experience. Six players were randomly assigned to the orthosis group, with four in the control group. Anthropometric data and baseline characteristics were recorded. A video analysis assessed elbow flexion angle during pitching at baseline and at 2 months. The frequency of orthosis wear was also tracked. Adverse events during twice-weekly practices were documented. Post-study surveys evaluated orthosis comfort, stability, and safety perceptions. In the orthosis group (n = 6), four participants showed improved elbow flexion angle, and two of the six participants showed almost no change. The overall median difference was 23.5°. In the control group (n = 4), three participants showed improvement, with a median improvement of 5.5°. Twelve adverse events, including pain, were reported by players not wearing orthoses, whereas no events occurred with orthosis use. Individual players in the control group or who did not wear the orthosis correctly experienced multiple episodes of pain from pitching over the study period. This preliminary study indicates a custom elbow orthosis can optimize pitching biomechanics and prevent adverse events in youth baseball players over the course of two months.

Relationship Between Arm Path, Ball Velocity, and Elbow Varus Torque in Professional Baseball Pitchers

Background

Currently, most pitching instructors suggest a shorter arm path-the total distance the arm travels during pitching. Theoretically, this combination allows for better body segment sequencing, a more efficient energy transfer through the kinetic chain, and increased ball velocity, while limiting elbow varus torque.

Hypothesis

Shorter arm paths would be associated with increased ball velocity and decreased elbow varus torque.

Study Design

Descriptive laboratory study.

Methods

A total of 182 professional pitchers threw 8 to 12 fastball pitches while evaluated by 3-dimensional motion capture (480 Hz). The arm path was calculated as the total distance the hand marker traveled during the pitch. The pitch was divided into early, late, and total arm paths. A linear regression model assessed the interpitcher relationship between arm path, elbow varus torque, and ball velocity. A linear mixed-effects model with random intercepts assessed intrapitcher relationships.

Results

Interpitcher comparison showed that total arm path weakly correlated with greater elbow varus torque (P = .025). Strong correlations were found between ball velocity and early (R2 = 0.788; P < .001), late (R2 = 0.787; P = .024), and total arm paths (R2 = 0.792; P < .001). Strong positive intrapitcher correlations were found between elbow varus torque and early (R2 = 0.962; P < .001) and total arm path (R2 = 0.964; P < .001). For individual pitchers, there was a large variation in the early (30.1 ± 15.7 cm) and late (21.4 ± 12.1 cm) arm path. For every 30-cm (11.8-inch) increase in early arm path (the mean range for an individual pitcher), there was a 1.29-N (β = 0.0429) increase in elbow varus torque and a 0.354 m/s (0.79 mph) (β = 0.0118) increase in ball velocity.

Conclusion

A shorter arm path correlated with decreased elbow varus torque and decreased ball velocity in intrapitcher comparisons. Determining the individual mechanics that decrease elbow varus torque may help coaches and trainers correct these patterns.

Clinical Significance

A shorter arm path during the pitch can decrease elbow varus torque, which limits the load on the medial elbow but also has a detrimental effect on ball velocity. An improved understanding of the impact of shortening arm paths on stresses on the throwing arm may help minimize injury risk.

Risk factors of throwing injuries related to pitching mechanics in young baseball players: a longitudinal cohort study

BACKGROUND

Risk factors for throwing injuries related to pitching mechanics are unknown. Insufficient pelvic rotation during pitching may be a risk factor for shoulder and elbow injury. This cohort study aimed to identify biomechanics risk factors for throwing injuries in young baseball players. We hypothesized that excessive mechanical load and motion errors would be risk factors for throwing injuries.

METHODS

Young baseball pitchers (aged 8-9 years) were recruited from regional baseball leagues between December 2016 and December 2019. Pitching measurements were performed before the start of each season and after the end of the last season in December 2019. The trunk tilt angular displacement, pelvic rotation angular displacement, and forearm rotation angle were calculated using a markerless motion capture system. We also measured elbow varus torque using an accelerometer. After the initial test session, each participant was followed up for 3 years to determine the occurrence of throwing injuries. Players with throwing shoulder and elbow injuries were categorized into the throwing injury group, and those without shoulder and elbow pain for 3 years were categorized into the noninjured group.

RESULTS

In this study, 97 baseball pitchers completed a 3-year follow-up. Among those participants, 66 (68.0%) had throwing injuries. A significant difference was observed between the throwing injury and noninjured groups, whereby the injured players had less pelvic rotation angular displacement.

CONCLUSION

Insufficient pelvic rotation during pitching is a newly discovered risk factor related to throwing injuries.

Magnitude and variability of individual elbow load in repetitive baseball pitching

In baseball pitchers the elbow is exposed to high and repetitive loads (i.e. external valgus torque), caused by pitching a high number of balls in a practice session or game. This can result in overuse injuries like the ulnar collateral ligament (UCL) injury. To understand injury mechanisms, the effect of repetitive pitching on the elbow load magnitude and variability was investigated. In addition, we explored whether repetitive pitching affects elbow muscle activation during pitching. Fifteen pitchers threw each 60 to 110 balls. The external valgus torque and electromyography of three elbow muscles were quantified during each pitch. Linear mixed model analyses were performed to investigate the effect of repetitive pitching. On a group level, the linear mixed models showed no significant associations of repetitive pitching with valgus torque magnitude and variability and elbow muscle activity. Significant differences exist between pitchers in their individual trajectories in elbow valgus torque and muscle activity with repetitive pitching. This shows the importance of individuality in relation to repetitive pitching. In order to achieve effective elbow injury prevention in baseball pitching, individual characteristics of changes in elbow load and muscle activity in relation to the development of UCL injuries should be investigated.

Biomechanical Basis of Interval Throwing Programs for Baseball Pitchers: A Systematic Review

Background

Interval throwing programs are used in rehabilitation of throwing injuries, especially ulnar collateral ligament injuries. Athletes who are rehabilitating begin by throwing on flat ground progressing through increasing distances, number of throws, and intensity of throwing. If the athlete is a baseball pitcher, the flat-ground throwing phase is followed by pitching on a mound at progressively increased effort. The goal is to build back arm strength and capacity with an emphasis on proper mechanics.

Purpose

To determine whether interval throwing progressively builds joint kinetics (specifically, elbow varus torque) to the level required during full-effort baseball pitching. A secondary purpose was to examine the kinematics produced during interval throwing compared to those seen during baseball pitching.

Study Design

Systematic Review.

Methods

Following PRISMA guidelines, PubMed, Embase, Web of Science, SPORTDiscus, and Google Scholar were systematically searched for biomechanical studies of flat-ground throwing and partial-effort pitching in baseball between 1987 and 2023. Studies that reported the biomechanics of either flat-ground throwing, or partial-effort pitching were included in this review. The AXIS tool was used to assess study quality.

Results

Thirteen articles met the inclusion criteria. Ten studies were determined to be of moderate quality, while three studies were deemed high quality. Elbow varus torque during partial-effort pitching was less than during full-effort pitching. Elbow varus torque for most flat-ground throws did not exceed full-effort pitching torque. While most studies showed increased elbow varus torque with increased flat-ground throwing distance, the distance at which elbow varus torque matched or exceeded full-effort pitching elbow varus torque was not consistent.As flat-ground throwing distance increased, shoulder external rotation angle and shoulder internal rotation velocity increased. Arm slot (forearm angle above horizontal) decreased as flat-ground throwing distance increased. For varied effort pitching, shoulder external rotation angle, shoulder internal rotation velocity, elbow extension velocity, and ball velocity increased as effort increased. While the front knee extended slightly from foot contact to ball release in full-effort pitching, the front knee flexed slightly during partial-effort pitching.

Conclusions

An interval throwing program progressively builds elbow varus torque up to levels produced in full-effort baseball pitching. While differences exist between interval throwing kinematics and pitching kinematics, the patterns are similar in general.

Level of Evidence

2.

Qualitative Research in Return to Sport: a Current Review of the Literature

PURPOSE OF REVIEW

Return to sport (RTS) is an important metric tied to patient satisfaction after receiving treatment for a sports-related injury. Recently, there has been an explosion of literature on RTS; yet a comprehensive review encompassing multiple injuries does not exist. Furthermore, RTS has historically been defined by quantitative measures that assess strength, function, and pain but little consideration has been given to psychologic factors nor has there been an open-ended forum for athletes to share with health care providers which factors they feel are most influential for RTS. This review also serves to heighten surgeons' awareness of underlying psychologic/psychosocial factors affecting RTS.

RECENT FINDINGS

Qualitative studies which employ open-ended questioning of athletes who have undergone surgical management of superior labral anterior-posterior (SLAP) tears, shoulder instability, ulnar collateral ligament (UCL) rupture, femoral acetabular impingement (FAI), and anterior cruciate ligament (ACL) tear demonstrate that fear of reinjury, lack of social support, and unrealistic expectations are all barriers to RTS. Qualitative studies give health care providers unique insight into the perspectives of their patients so that unmet postoperative needs can be addressed to facilitate RTS. Sports psychologists, coaches, athletic trainers, and physical therapists should create a positive environment to address these needs and provide optimal, holistic care to return athletes to the field safely. Though time consuming, further qualitative research is necessary to understand the unique factors affecting RTS in athletes.

OpenCap: Human movement dynamics from smartphone videos

Measures of human movement dynamics can predict outcomes like injury risk or musculoskeletal disease progression. However, these measures are rarely quantified in large-scale research studies or clinical practice due to the prohibitive cost, time, and expertise required. Here we present and validate OpenCap, an open-source platform for computing both the kinematics (i.e., motion) and dynamics (i.e., forces) of human movement using videos captured from two or more smartphones. OpenCap leverages pose estimation algorithms to identify body landmarks from videos; deep learning and biomechanical models to estimate three-dimensional kinematics; and physics-based simulations to estimate muscle activations and musculoskeletal dynamics. OpenCap's web application enables users to collect synchronous videos and visualize movement data that is automatically processed in the cloud, thereby eliminating the need for specialized hardware, software, and expertise. We show that OpenCap accurately predicts dynamic measures, like muscle activations, joint loads, and joint moments, which can be used to screen for disease risk, evaluate intervention efficacy, assess between-group movement differences, and inform rehabilitation decisions. Additionally, we demonstrate OpenCap's practical utility through a 100-subject field study, where a clinician using OpenCap estimated musculoskeletal dynamics 25 times faster than a laboratory-based approach at less than 1% of the cost. By democratizing access to human movement analysis, OpenCap can accelerate the incorporation of biomechanical metrics into large-scale research studies, clinical trials, and clinical practice.

Kinematic and Kinetic Comparisons of Arm Slot Position Between High School and Professional Pitchers

Background

Throwing arm kinetics differ in pitchers at varying arm slot (AS) positions (frontal-plane arm position at ball release relative to the vertical axis).

Purpose

To determine how kinematic and kinetic values differ between professional and high school pitchers with varying AS positions, and whether these differences are similarly observed in both populations.

Methods

High school (n = 130) and professional (n = 288) pitchers threw 8 to 12 fastballs under 3-dimensional motion capture technology. Pitchers in each cohort were subdivided based on mean AS position at ball release: AS1 (least degree of AS: most overhand throwing styles), AS2 (intermediate degree of AS: three-quarter throwing styles), or AS3 (greatest degree of AS: most sidearm throwing styles). Kinetic and kinematic parameters were compared between groups.

Study Design

Controlled laboratory study.

Results

High school pitchers had a more overhand AS at ball release (50° ± 11°) compared with professional pitchers (58° ± 14°) (P < .001). In both cohorts, AS1 pitchers had significantly greater shoulder abduction (high school, P <0.001; professional, P <0.0001) and lateral trunk flexion (high school, P < 0.001; professional, P <0.0001) at ball release compared with AS3 pitchers. Professional pitchers with an AS3 position had significantly delayed timing of maximum upper trunk angular velocity compared with AS1 pitchers (64% ± 7% vs 57% ± 7% of pitch time, respectively; P < .0001). A significant positive correlation between AS and elbow flexion torque was found in high school pitchers (P = .002; β = 0.28), and a significant negative correlation between AS and elbow varus torque (P < .001; β = -0.22) and shoulder internal rotation torque (P < .001; β = -0.20) was noted in professional pitchers.

Conclusion

AS position was related to shoulder abduction and trunk lateral tilt. Professional and high school pitchers with varying AS positions did not experience similar changes in throwing arm kinetics.

Clinical Relevance

In professional pitchers, the earlier onset of maximum upper trunk angular velocity with overhand throwing style may reflect inappropriate pelvis-trunk timing separation, a parameter implicated in upper extremity injury, and the negative correlation between AS and elbow varus and shoulder internal rotation torque suggests that both excessive and minimal AS positions have negative implications.

Energy flow in men's javelin throw and its relationship to joint load and performance

Background

Performance in javelin throwing is dependent on the release speed and therefore the energy transferred to the javelin. Little is known about the flow of mechanical energy in javelin throwing and whether there is a connection to joint loading and throwing performance. The purpose of the study was therefore to investigate (1) the energy flow within the kinetic chain of the throwing arm, (2) how it is related to performance and joint loads and (3) how joint forces and torques are used to transfer, generate and absorb mechanical energy.

Methods

The kinematics of 10 experienced javelin throwers were recorded using a 12-camera infrared system. 16 markers were placed on the athlete's body, five on the javelin to track the movement of each segment. A segmental power analysis was carried out to calculate energy flow between upper body, upper arm, forearm and hand. Stepwise regression analysis was used to calculate the variable that best predicts release speed and joint loads.

Results

The results indicate that the higher the peak rate of energy transfer from the thorax to the humerus, the higher the release speed and the joint loads. While there were no differences between the peak rate of energy transfer in the different joints, the energy transferred differed depending on whether joint forces or torques were used. It can be further shown that higher joint torques and thus higher rotational kinetics at the shoulder are linked to higher release speeds. Thus, the movements of the upper body can be of great influence on the result in javelin throwing. Furthermore, the data show that athletes who are able to transfer more energy through the shoulder, rather than generate it, experience a smaller joint loading. An effective technique for improved energy transfer can thus help perform at the same level while lowering joint stress or have higher performance at the same joint loading.

A novel method intersecting three-dimensional motion capture and medial elbow strength dynamometry to assess elbow injury risk in baseball pitchers

In baseball pitching, resultant elbow varus torque reaches the peak value of 50-120 N m, exceeding the joint failure limit that risks damage to the ulnar collateral ligament (UCL). In-vivo methodology is lacking to assess whether pitchers have sufficient muscular strength to shield UCL and how strongly the elbow musculature must contract to minimize valgus loading on UCL. This study introduces a method to assess relative percentages of muscular varus strength required to unload the UCL. The maximum voluntary isometric varus strength (MVIVS) produced by the medial elbow musculature and the maximum resultant varus torques at elbow in pitching fastballs and other types were measured for two professional pitchers. Simulation was conducted to determine the relative percentages of MVIVS required to unload the UCL to varying degrees and the impact of athletes' previous UCL reconstruction on the relative percentages was examined. The maximum resultant varus torque in pitching was found to range 72-97%MVIVS depending on the type of pitch. The elbow musculature had to produce 21-49%MVIVS to avoid acute failure of intact UCL whereas the corresponding requirements were 39-63%MVIVS for UCL reconstructed joint. The method offers new insight into baseball pitcher's training/rehabilitation and physical assessment to reduce the risk of UCL injury.

Comparison of the "Tall and Fall" Versus "Drop and Drive" Pitching Styles: Analysis of Major League Baseball Pitchers During a Single Season

Background

Previous research has documented the proportion of "tall and fall" (TF) and "drop and drive" (DD) pitching styles among Major League Baseball (MLB) pitchers who underwent ulnar collateral ligament reconstruction (UCLR). The proportion of these 2 styles among all MLB pitchers remains unknown.

Purpose

To determine the proportion of the TF and DD pitching styles in all rostered MLB pitchers during a single season as well as the proportion of TF and DD pitchers who sustained an upper extremity (UE) injury and those who underwent UCLR.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

Pitcher demographic characteristics from the 2019 MLB season and pitching information were obtained via open-access sources. Two-dimensional video analysis was used to categorize the included pitchers into TF and DD groups. Statistical comparisons and contrasts were made using 2-tailed t tests, chi-square tests, and Pearson correlation analyses as appropriate.

Results

Of the 660 MLB rostered pitchers in 2019 (age, 27.39 ± 3.51 years; body mass index, 26.34 ± 2.47 kg/m²; fastball velocity, 150.49 ± 3.99 kph [93.51 ± 2.48 mph]), 412 (62.4%) pitchers used the TF style and 248 (37.6%) pitchers used the DD style. Significantly more UE injuries were seen in the TF group compared with the DD group (112 vs 38 injuries, respectively; P < .001). Twelve pitchers underwent UCLR (TF, 10; DD, 2), representing a 1.8% UCLR rate among all pitchers. This was a second surgery for 2 pitchers, both of whom used the TF pitching style. Significantly more pitchers in the TF group than the DD group had undergone UCLR before 2019 (135 vs 56 pitchers, respectively; P = .005).

Conclusion

The results of the present study demonstrated a higher prevalence of both UE injury and prior UCLR in TF pitchers. Further research is needed to explore the potential association between pitching style and UE injury.

Increased Medial Elbow Torque Is Associated With Ball Velocity Rather Than a History of Medial Elbow Injuries in Youth Baseball Pitchers

PURPOSE

This study compared medial elbow torque in youth baseball pitchers with and without a history of medial elbow injuries to determine the relationship between medial elbow torque during pitching and having a history of medial elbow injuries.

METHODS

We recruited 171 youth baseball pitchers aged 9 to 12 years old. The exclusion criteria included current pain with pitching, history of surgery on the tested extremity, or osteochondritis dissecans of the humeral capitellum. The participants were grouped into 3 groups: injury <1-year, injury >1-year, and control, based on ultrasonographic abnormalities of the elbow and the presence of elbow pain. Pitchers pitched 3 fastballs while wearing a sensor sleeve that recorded the medial elbow torque, arm speed, and shoulder rotation. Ball velocity was measured using a radar gun.

RESULTS

The final analysis included 164 pitchers. Thirty were assigned to the injury <1-year group, 34 to the injury >1-year group, and 100 to the control group. The medial elbow torque was significantly greater in the injury <1-year group compared with the control group (18.6 ± 3.6 Nm vs 16.2 ± 4.8 Nm, P = .023). A multiple regression analysis revealed that ball velocity (B = 0.282, P < .001) and body weight (B = -0.224, P < .001) were significantly associated with medial elbow torque, but not with the history of medial elbow injuries.

CONCLUSIONS

Increased medial elbow torque was associated with greater ball velocity regardless of the history of medial elbow injuries. Youth baseball pitchers with a history of medial elbow injuries within one year had greater medial elbow torque during pitching; however, having a history of medial elbow injuries was not an independent factor in increasing medial elbow torque. Limiting the ball velocity can reduce medial elbow torque and may prevent elbow injuries in youth baseball pitchers.

LEVEL OF EVIDENCE

Level II, prospective comparative prognostic investigation with the patients enrolled at different time point.

Hip Strength and Pitching Biomechanics in Adolescent Baseball Pitchers

CONTEXT

Hip strength may influence the energy flow through the kinematic chain during baseball pitching, affecting athlete performance as well as the risk for injury.

OBJECTIVE

To identify associations between hip strength and pitching biomechanics in adolescent baseball pitchers during 3 key events of the pitching cycle.

DESIGN

Cross-sectional study.

SETTING

Biomechanics laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 26 adolescent male baseball pitchers (age = 16.1 ± 0.8 years, height = 184.29 ± 5.5 cm, mass = 77.5 ± 8.5 kg).

MAIN OUTCOME MEASURE(S)

The main outcome measure was hip strength (external rotation, internal rotation, flexion, abduction, adduction, and extension). After strength measurements were acquired, motion capture was used to obtain a full-body biomechanical analysis at 3 events during the pitching cycle (foot contact, maximal external rotation, and ball release). We then evaluated these values for associations between hip strength and pitching biomechanics. Scatterplots were examined for linearity to identify an appropriate correlation test. The associations were linear; thus, 2-tailed Pearson correlation coefficients were used to determine correlations between biomechanical metrics. An α level of .01 was chosen.

RESULTS

Ten strong correlations were found between pitching biomechanics and hip strength: 8 correlations between hip strength and kinematics at key points during the pitch and 2 correlations of hip strength with peak elbow-varus torque.

CONCLUSIONS

Several correlations were noted between lower extremity strength and pitching biomechanics. This information provides data that may be used to improve performance or reduce injury (or both) in pitchers. Increased hip strength in adolescent pitchers may both improve performance and decrease the risk of injury.

Effects of Contralateral Trunk Tilt on Shoulder and Elbow Injury Risk and Pitching Biomechanics in Professional Baseball Pitchers

BACKGROUND

Baseball pitchers employ various contralateral trunk tilt (CTT) positions when pitching depending on if they have an overhand, three-quarter, or sidearm delivery. There are no known studies that have examined how pitching biomechanics are significantly different in professional pitchers with varying amounts of CTT, which may provide insight into shoulder and elbow injury risk among pitchers with different CTT.

PURPOSE

To assess differences in shoulder and elbow forces and torques and baseball pitching biomechanics in professional pitchers with maximum 30° to 40° CTT (MaxCTT), moderate 15° to 25° CTT (ModCTT), and minimum 0° to 10° CTT (MinCTT).

STUDY DESIGN

Controlled laboratory study.

METHODS

In total, 215 pitchers were examined, including 46 pitchers with MaxCTT, 126 pitchers with ModCTT, and 43 pitchers with MinCTT. All pitchers were tested using a 240-Hz, 10-camera motion analysis system, and 37 kinematic and kinetic parameters were calculated. Differences in kinematic and kinetic variables among the 3 CTT groups were assessed with a 1-way analysis of variance (P < .01).

RESULTS

Maximum shoulder anterior force and maximum elbow proximal force were significantly greater in ModCTT (403 ± 79 N) than MaxCTT (369 ± 75 N) and MinCTT (364 ± 70 N), while maximum elbow flexion torque and shoulder proximal force, respectively, were significantly greater in ModCTT (69 ± 11 N·m and 1176 ± 152 N, respectively) than MaxCTT (62 ± 12 N·m and 1085 ± 119 N, respectively). During arm cocking, maximum pelvis angular velocity was greater in MinCTT than MaxCTT and ModCTT, and maximum upper trunk angular velocity was greater in MaxCTT and ModCTT than MinCTT. At ball release, trunk forward tilt was greater in MaxCTT and ModCTT than MinCTT and greater in MaxCTT than ModCTT, while arm slot angle was less in MaxCTT and ModCTT than MinCTT and less in MaxCTT than ModCTT.

CONCLUSION

The greatest shoulder and elbow peak forces occurred in ModCTT, which occurs in pitchers who throw with a three-quarter arm slot. More research is needed to assess if pitchers with ModCTT are at a higher risk of shoulder and elbow injury compared with pitchers with MaxCTT (overhand arm slot) and MinCTT (sidearm arm slot), although in the pitching literature, excessive elbow and shoulder forces and torques have been shown to correlate with elbow and shoulder injuries.

CLINICAL RELEVANCE

The results from the current study will help clinicians better understand if differences in kinematic and kinetic measures differ with pitching, or if differences in force, torque, and arm position occur at different arm slots.

Editorial Commentary: Elbow Injury Results When Pediatric and Adolescent Throwing Athletes Throw as Hard as Possible, and Weighted Baseball Training Should Be Banned for Youth Athletes

We are in the middle of an epidemic involving pediatric and adolescent throwing athletes. Too many young athletes have elbow injuries, and it is unnerving how young surgical indications can present. Increased competition has led to increased demands before athletes have reached their full adult size. Evidence shows that higher ball velocity, higher shoulder external rotation angle, and higher arm speed are associated with increased medial elbow torque and elbow injury in this population. Pediatric and adolescent athletes should not try to throw as hard as possible, and weighted baseball training should be banned for youth athletes.

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.

The influence of modeling parameters for computing joint kinetics in adolescent and adult pitchers

Baseball pitching is a well-studied area of sports biomechanics partially due to high upper extremity (UE) injury rates. Joint kinetics have not been linked directly to UE injury in pitchers but are often used in lieu of injury data as a proxy for injury risk. Pitchers exhibit adaptations in the throwing arm that may affect body segment inertial parameters (BSIPs); however, these are unaccounted for in traditional modelling methods and may contribute to the lack of evidence linking joint kinetics to injury. Therefore, this study aimed to describe the BSIPs of the throwing arm in adolescent and adult pitchers and compare joint kinetics computed from traditional modelling methods to those using individualised BSIPs. Forty-five pitchers underwent dual-energy X-ray absorptiometry (DXA) scans and motion capture sessions in a biomechanics laboratory. Individual BSIPs from the DXA scans were used to estimate UE joint kinetics via inverse dynamics and compared to joint kinetics computed from scaled BSIPs. Throwing arm BSIPs in pitchers were significantly different from studies of the general population. Variable levels of agreement and significant differences in joint kinetics existed between methods, indicating that using joint kinetics computed via scaled models to identify pitchers at risk of injury may be inappropriate.

Comparison of Trunk and Pelvic Kinematics in Youth Baseball Pitchers With and Without Upper Extremity Pain: A Cross-Sectional Study

Background

Motion of the pelvis and trunk during baseball pitching is associated with increased upper extremity (UE) kinetics. Increased kinetics on the UE may lead to throwing-arm pain in youth pitchers. Limited biomechanical comparisons have been conducted on youth pitchers with and without throwing-arm pain to identify mechanical risk factors associated with pain.

Purpose

To examine trunk and pelvic kinematics in youth baseball pitchers with and without UE pain.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

A total of 26 male youth baseball pitchers (mean age, 12.7 ± 1.5 years; mean height, 162.2 ± 12.9 cm; mean weight, 52.6 ± 13.1 kg) were recruited to participate. An electromagnetic tracking system was used to obtain kinematic data during the fastball pitch. Data from a health history questionnaire was examined. Participants who answered "yes" to experiencing pain and who selected a region on their UE as the pain location were placed into the UE pain group. Participants who responded "no" to experiencing pain were placed into the pain-free group. We compared between-group differences in trunk rotation, flexion, and lateral flexion; pelvic rotation, anteroposterior tilt, and lateral tilt; and hip-shoulder separation from peak knee height to ball release of the baseball pitch using 1-dimensional statistical parametric mapping with an alpha level set at .05.

Results

No statistically significant differences were observed between the UE pain and pain-free groups in the 7 trunk and pelvic kinematics analyzed from peak knee height to ball release (P > .05).

Conclusion

Trunk and pelvic kinematics during the pitching motion did not differ between pain and pain-free groups of youth baseball pitchers.

Kinematic and kinetic comparison between preprofessional pitchers from the Dominican Republic and the United States

Introduction

Pitching biomechanical efficiency is defined as the association between pitch velocity and arm kinetics. Pitching mechanics inefficiency, an increase in arm kinetics without the resultant increase in pitch velocity, can lead to increased arm strain, increasing arm injury risk. The purpose of this study was to compare arm kinetics, elbow varus torque and shoulder force, in preprofessional United States (US) and Dominican Republic (DR) pitchers. Kinematics that are known to influence elbow varus torque and shoulder force as well as a representative of pitch velocity (hand velocity) were also compared.

Methods

A retrospective review was performed on baseball pitchers from the DR and US who participated in biomechanical evaluations conducted by the University biomechanics laboratory personnel. Three-dimensional biomechanical analyses were performed on US (n = 37) and DR (n = 37) baseball pitchers. Potential differences between US and DR pitchers were assessed through analysis of covariance with 95% confidence intervals [95% confidence Interval (CI)].

Results

Preprofessional DR pitchers experienced increased elbow varus torque compared with their US counterparts [DR: 7.5 (1.1); US: 5.9 (1.1) %BWxH; Beta: -2.0 (95% CI: -2.7, -1.2) %BWxH], despite throwing fastballs with slower hand velocity [DR: 3,967.1 (939.4); US: 5,109.1 (613.8) °/s; Beta: 1,129.5 (95% CI: 677.5, 1,581.4) °/s]. DR and US pitchers demonstrated similar shoulder force [DR: 136.8 (23.8); US: 155.0 (25.7); Beta: 0.4 (95% CI: -1.2, 19.7) %BW].

Discussion

Increased elbow varus torque although decreased hand velocity suggests inefficient pitching mechanics among DR pitchers. Inefficient pitching mechanics and increased elbow torque should be considered when developing training programs and pitching plans for professional pitchers from the Dominican Republic.

Pitching mechanics and performance of adult baseball pitchers: A systematic review and meta-analysis for normative data

OBJECTIVES

The aim of this systematic review was to critically review and synthesise the findings from primary studies on pitching mechanics and performance of healthy adult baseball pitchers.

DESIGN

Systematic review with meta-analysis.

METHODS

Eight English- and Japanese-language databases were systematically searched from inception to 22nd July 2022.

RESULTS

In total, 29 descriptive biomechanical studies were included. Overall study quality was moderate. In subgroup analyses, professional pitchers showed significantly higher stride length, peak shoulder internal rotation velocity, peak shoulder proximal force and ball velocity compared to collegiate pitchers. Conversely, collegiate pitchers were found to have significantly higher peak pelvis rotation velocity.

CONCLUSIONS

Available normative data suggested potentially heterogeneous pitching mechanics and performance between professional and collegiate pitchers. However, the findings in this review should be interpreted cautiously. Since statistical heterogeneity was significant within most data sets, more detailed subgroup analyses are required. Additionally, more high-quality studies utilising measurement systems with established reliability are required to obtain accurate data in baseball pitching mechanics and performance.

Shoulder stretching versus shoulder muscle strength training for the prevention of baseball-related arm injuries: a randomized, active-controlled, open-label, non-inferiority study

Glenohumeral internal rotation deficit (GIRD) and weakness in prone external rotation are risk factors for shoulder and elbow injuries in high school baseball pitchers. While a shoulder-stretching prevention program to improve GIRD decreases the injury rate, the effects of external rotation strength remain unclear. This non-inferiority (NI) study investigates the hypothesis that external rotation strength training is not inferior to sleeper stretching for shoulder and elbow injury prevention in high school baseball pitchers. Participants were randomly allocated to the stretching (n = 62; active control group) and muscle-training (n = 51) groups. Specific exercises were performed each night. Elbow and shoulder injuries were monitored for 150 days. Kaplan-Meier survival curves were generated, and the hazard ratios (HRs) for injury occurrence were calculated using multivariate Cox regression. The log-rank test was used to compare the injury-free time. A one-sided NI test using a fixed NI margin was performed (significance level, P = 0.025). The injury rates were 22.6% (n = 14) in the stretching group and 9.8% (n = 5) in the muscle-training group. The muscle-training group had a lower injury rate (P < 0.001) and a lower risk of injury than the stretching group (HR = 0.489). Therefore, external rotation muscle strength training is not inferior to stretching for preventing baseball-related arm injuries.

Retrospective Analysis of Ulnar Collateral Ligament Reconstructions in Major League Baseball Pitchers: A Comparison of the "Tall and Fall" Versus "Drop and Drive" Pitching Styles

Background

Previous pilot research has investigated differences in elbow valgus torque between the "tall and fall" (TF) and "drop and drive" (DD) pitching styles. Whether one of these pitching styles is associated with a greater rate of ulnar collateral ligament reconstruction (UCLR) is currently unknown.

Purpose

To determine the proportion of Major League Baseball (MLB) pitchers using the TF and DD pitching styles who underwent UCLR over a 10-year period.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

The demographic characteristics of pitchers who underwent UCLR between 2007 and 2017 were obtained via the open-source database MLB Player Analysis Tommy John Surgery List. Other information, such as previous UCLR and pitching videos and graphics, was obtained from other open-source databases. A comprehensive, 2-dimensional, kinesiology-based multicomponent definition of each pitching style was formulated and used to categorize the included pitchers into the TF and DD groups. Statistical comparisons and contrasts were made using chi-square and Pearson correlation tests.

Results

Included were 223 MLB pitchers (mean ± SD age, 27.5 ± 3.6 years; body mass index [BMI], 27.6 ± 2.2; throwing velocity, 92.9 ± 2.6 mph [149.5 ± 4.2 km/h]) who underwent UCLR between 2007 and 2017. Of these pitchers, 162 were categorized as TF pitchers (72.6%) and 61 as DD pitchers (27.4%). Pitching velocity for injured pitchers was significantly correlated to BMI (P < .001). We found no significant associations of pitching style with year of UCLR (P = .941), BMI (P = .549), age (P = .647), handedness (P = .501), or average pitch velocity (P = .921).

Conclusion

The study findings demonstrated that a higher proportion of UCL-injured MLB pitchers (72.6%) used the TF pitching style. Further research is needed to explore the potential association between pitching style and UCL injury.

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.

The influence of excessive ipsilateral trunk tilt on upper-extremity throwing mechanics: a newly characterized parameter for biomechanical evaluation in high school and professional pitchers

BACKGROUND

Although contralateral trunk tilt has been recognized, the phenomenon of excessive ipsilateral trunk tilt, often observed during earlier portions of the pitch, has not been explored as a potential correlate with throwing-arm kinetics among baseball pitchers. The purpose of this study was to evaluate kinetic and kinematic parameters among high school and professional pitchers related to excessive ipsilateral and contralateral trunk tilt.

METHODS

Professional and high school pitchers were assessed with a 3-dimensional motion capture system (480 Hz) while pitching. Pitchers were grouped as follows: excessive ipsilateral tilt at foot contact (FC), neutral, or excessive contralateral tilt at ball release (BR). Trunk and shoulder kinematics as well as throwing-arm kinetics were compared between subgroups via post hoc regression analysis.

RESULTS

Professional pitchers (n = 287) had significantly higher ipsilateral trunk tilt at FC (P < .001) than high school pitchers (n = 59). High school pitchers with excessive contralateral trunk tilt at BR experienced significantly higher shoulder superior force (27.0% ± 7.4% body weight [BW] vs. 17.6% ± 5.1% BW, P < .001) and shoulder anterior force (39.6% ± 8.2% BW vs. 35.7% ± 5.4% BW, P < .001) compared with the ipsilateral trunk tilt cohort but had comparable ball velocity (30.2 ± 3.2 m/s vs. 30.4 ± 2.1 m/s, P = .633). For professionals, for every 10° increase in ipsilateral trunk tilt at FC, ball velocity increased by 0.2 m/s (B = 0.02, β = 0.07, standard error [SE] = 0.005, P = .010) whereas elbow varus torque decreased by 0.1% BW × height (B = -0.01, β = -0.08, SE = 0.002, P < .001) and shoulder internal rotation torque decreased by 0.1% BW × height (B = -0.01, β = -0.07, SE = 0.002, P = .005).

CONCLUSION

High school and professional pitchers with excessive ipsilateral trunk tilt at FC consistently demonstrated significantly decreased throwing-arm kinetics (shoulder anterior force and shoulder superior force for high school pitchers and shoulder internal rotation torque and elbow varus torque for professional pitchers) compared with pitchers with excessive contralateral trunk tilt at BR, with equivalent ball velocity. In addition, professional pitchers appeared to engage in significantly greater ipsilateral trunk tilt during early portions of the pitch when compared with high school pitchers, which may represent a kinetically favorable method adopted by pitchers at higher playing levels to maintain adequate ball velocity while concomitantly minimizing throwing-arm kinetics.

Evaluating Pelvis Rotation Style at Foot Contact: A Propensity Scored Biomechanical Analysis in High School and Professional Pitchers

BACKGROUND

Early pelvis rotation has been associated with decreased throwing arm kinetics and conventionally was considered a component of proper pitching form in baseball throwers. However, previous assessments of pelvis rotation style have not accounted for confounders such as playing level, anthropometric characteristics, or ball velocity and have not evaluated sufficient sample sizes.

PURPOSE

To compare kinetic and kinematic parameters based on pelvis rotation style in high school and professional pitchers.

STUDY DESIGN

Descriptive laboratory study.

METHODS

High school and professional baseball pitchers threw 8 to 12 fastball pitches while being evaluated using 3-dimensional motion capture (480 Hz). These pitchers were 1:1 propensity score matched by age, height, weight, handedness, and ball velocity based on early (<60°) versus late (≥60°) pelvis rotation style at foot contact. A total of 26 kinematic and 10 kinetic parameters were compared between groups. The kinematic parameters were used to conduct a linear regression between early and late pelvis rotation at foot contact.

RESULTS

Pelvis rotation at foot contact was not significantly associated with ball velocity for either high school (P = .243) or professional pitchers (P = .075). No difference was found in elbow varus torque between high school early rotators (57.5 ± 14.9 N·m) and late rotators (51.3 ± 14.7 N·m; P = .036) and between professional early rotators (80.1 ± 11.8 N·m) and late rotators (79.0 ± 11.2 N·m; P = .663). At foot contact in high school pitchers, stride length increased by 2.1% of body height (B = -0.205; β = -0.470; P < .001), trunk rotation increased by 4.2° (B = -0.417; β = -0.488; P < .001), and trunk flexion at foot contact decreased by 4.4° (B = 0.442; β = 0.476; P < .001) with every 10° increase in pelvis rotation. At foot contact in professional pitchers, stride length increased by 2.3% of body height (B = -0.229; β = -0.478; P < .001), trunk rotation increased by 4.3° (B = -0.431; β = -0.515; P < .001), and trunk flexion decreased by 4.0° (B = 0.404; β = 0.373; P < .001) with every 10° increase in pelvis rotation.

CONCLUSION

Pelvis rotation at foot contact was associated with several kinematic parameters in both groups and may influence mechanics further along the kinetic chain. Landing open or closed was not significantly associated with throwing arm kinetics or ball velocity for both high school and professional baseball pitchers, contrary to previous thought.

CLINICAL RELEVANCE

Coaches and players may better focus their efforts on refining other kinematic parameters for enhanced performance outcomes and safe pitching mechanics.

Quantifying Within-Individual Elbow Load Variability in Youth Elite Baseball Pitchers and Its Role in Overuse Injuries

Medial elbow overuse injuries are rising in baseball. The external valgus torque magnitude is a possible risk factor for medial elbow injuries. The magnitude on its own cannot explain why one pitcher sustains an injury and another does not. Therefore, the aim of this study is to describe the within-individual external valgus torque variability and to determine whether the within-individual external valgus torque variability can be described by a Gaussian distribution. Eleven youth elite baseball pitchers threw twenty-five fastball pitches. Body kinematics were measured with VICON motion capture at 400 Hz. Elbow valgus torques of the total 270 pitches were calculated with a custom-made inverse dynamic model in Python. Visual inspection and the Shapiro–Wilk test were performed to test for the within-individual elbow valgus torque normality. The results showed that within-individual valgus torque variability was present in pitchers and differed among pitchers. Furthermore, it was shown that the within-individual valgus torque variability was normally distributed in nine out of eleven subjects. In conclusion, the presence of and differences in within-individual elbow load variability among baseball pitchers can be useful variables as they might be related to overuse elbow injuries.

Residual Effects of Glenohumeral Range of Motion, Strength, and Humeral Retroversion on Prior Overhead Athletes After Cessation of Sport

Background:

Research has shown that repetitive stress from playing an overhead (OH) sport can cause musculoskeletal and osseous adaptations to occur on the dominant side. Additionally, there are limited data about the residual effects of these adaptations after the cessation of sports participation.

Purpose:

To investigate the effects of prior participation in an OH sport versus not participating in an OH sport on glenohumeral range of motion (ROM), isometric strength, and humeral retroversion (HR).

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

Forty-eight college-aged individuals participated. Participants were split into 2 groups: (1) individuals who previously participated in an OH sport (n = 20; age, 20.3 ± 1.1 years; height, 166.3 ± 15.27 cm; weight, 72.2 ± 13.5 kg) and (2) individuals who previously did not play an OH sport (n = 28; age, 20.6 ± 0.9 years; height, 168.8 ± 6.3 cm; weight, 68.1 ± 15.1 kg). After completing a health history questionnaire, the following were measured: side-to-side shoulder internal rotation (IR) and external rotation (ER) ROM via an inclinometer, isometric shoulder strength via a handheld dynamometer, and HR using an ultrasound imaging machine. A Mann-Whitney U test was used to determine group differences, and a Wilcoxon t test was used to analyze side-to-side differences within each group.

Results:

The Mann-Whitney U test revealed a statistically significant group difference for dominant shoulder ER ROM (U = 162.00, P = .014). Specifically, the prior OH group had significantly more ER than the control group. Within the prior OH group, testing revealed that athletes had significantly more HR (Z =–2.782, P = .005), ER ROM (Z =–1.979, P = .048), and ER isometric strength (Z =–2.763, P = .006) on their dominant than nondominant shoulder and significantly less IR ROM (Z =–3.099, P = .002) on their dominant than nondominant shoulder.

Conclusion:

Prior OH sports participation may have residual osseous and musculoskeletal effects that remain after cessation of the sport.

Joint and segment sequencing and its relationship to ball velocity and throwing arm kinetics in professional pitchers

BACKGROUND

Temporal variations during the pitch have demonstrated significant impacts on the kinetic chain, and as such, have implications in injury risk.

PURPOSE

To determine the effect of varying chronological orders of maximum joint and segment velocities on ball velocity and upper extremity kinetics.

METHODS

Professional baseball pitchers (n = 287) were assessed with 3D-motion capture (480 Hz) while pitching. Pitches were categorized into one of the following groups dependent on the first maximum joint or segment velocity achieved out of chronological order in an inferior to superior direction: knee extension (DscK), pelvis rotation (DscP), trunk rotation (DscT), shoulder rotation (DscS), forearm pronation (DscF), and Proper (for pitchers with the correct temporal sequence), and Total Population, for all pitchers. Ten normalized throwing arm kinetic variables were compared among groups. Regression analysis was conducted on the timing of maximum velocities with ball velocity.

RESULTS

The majority of pitches were in the DscK group (64.5%). The DscK group had a significantly slower maximum lead knee extension velocity compared with the Proper group (253°/s vs. 316°/s, P = .017). The Proper group had a significantly faster ball velocity compared with the Total Population (39.0 ± 1.9 m/s vs. 38.3 ± 2.1 m/s, P = .013). The DscP group had a significantly slower maximum pelvis rotation velocity compared with the Proper group (596°/s vs. 698°/s, P < .001). The Proper group had no significant difference in kinetics relative to the population. For every 1 standard deviation delay in attaining maximum lead knee extension velocity, ball velocity increased by 0.38 m/s (B = 3.5, β = 0.18, P < .001). For every 1 standard deviation delay in timing to achieve maximum pelvis rotation velocity, maximum pelvis rotation velocity and ball velocity increased by 22.5°/s (B = 1107.0, β = 0.23, P < .001) and 0.48 m/s (B = 23.4, β = 0.23, P < .001), respectively.

CONCLUSION

Pitchers with a discordant sequence of knee extension and pelvis rotation velocity timing had significantly slower corresponding segment/joint velocities. Conversely, pitchers with a proper sequence had the fastest ball velocity with minimal differences in throwing arm kinetics. To maximize ball velocity, professional pitchers should consider achieving maximal velocities in an inferior to superior chronological sequence, with a particular focus on the knee and pelvis.

Effect of Clubbell Training on Glenohumeral Internal and External Rotation, Muscle Function, and Ball Velocity in Baseball Pitchers

OBJECTIVES This study examined the effects of clubbell exercises in a pitcher training program on the range of motion (ROM), muscle function, and its subsequent influence on pitching velocity. Additionally, this study aimed to develop an optimal training program to prevent injury while improving pitcher performance.METHODS Eighteen pitchers were included and equally divided into clubbell exercise and control groups. Clubbell training was conducted through 60-minute sessions twice a week for 12 weeks. Internal/external rotational (IR/ER) ROM, IR/ER muscle strength, muscle endurance, muscle power, and pitching velocity were measured before and after the intervention.RESULTS The IR (<i>p</i> = 0.051) and total ROM (TROM; <i>p</i> = 0.05) of the throwing arm decreased in the control group but increased in the clubbell exercise group, with an observed tendency of interaction. In the non-throwing arm, the ER ROM was significantly different between the two groups (<i>p</i> <0 .05), also with an observed tendency of interaction (<i>p</i> = 0.055). IR peak torque per body weight at 60°/sec significantly increased in both groups over the exercise period (<i>p</i> < 0.01). Total work per body weight and average power of IR at 180°/sec increased in both groups over the exercise period (<i>p</i> < 0.01). The pitching velocity decreased in both groups throughout the exercise period (<i>p</i> < 0.05).CONCLUSIONS Although 12 weeks of clubbell training had limited effects on ROM, the findings revealed that this exercise could be effective in improving pitching performance, preventing injuries, and maintaining long-term performance. Further studies are recommended for a more detailed assessment.

Decreased Trunk Rotation at Foot Contact in Professional Baseball Pitchers With Prior Conservatively Managed SLAP Tears: A Propensity Score-Matched Analysis

PURPOSE

To compare kinematic and kinetic parameters between a cohort of fully recovered professional pitchers with prior shoulder injury treated conservatively and a cohort with no prior shoulder injury.

METHODS

Twenty-six fully recovered professional baseball pitchers with a history of shoulder injury treated conservatively pitched 8 to 10 fastball pitches using 3-dimensional motion capture (480 Hz). All shoulder injuries occurred within a 1- to 4-year time span from biomechanical evaluation and were severe enough to prevent pitchers from playing for between 1 and 12 months. These pitchers were propensity score matched by age, height, weight, handedness, and ball velocity to pitchers with no prior injury history (control) at a ratio of 1:4. We compared 21 kinematic and 11 kinetic parameters between groups using appropriate parametric testing. Subanalysis comparisons of pitchers with prior SLAP injury as well as rotator cuff tendinitis were also performed.

RESULTS

SLAP tears (n = 11, 42.3%) were the most frequently reported injury, followed by rotator cuff tendinitis and/or shoulder impingement (n = 7, 26.9%). Compared with the control group, the 26 pitchers with prior injury showed no significant differences across the kinematic and kinetic factors. However, the SLAP tear subgroup did show significantly less trunk rotation at foot contact compared with controls (34.1° ± 4.9° vs 39.2° ± 10.2°, P = .0075).

CONCLUSIONS

Fully recovered professional baseball pitchers with shoulder injuries treated conservatively showed no significant differences in kinetics or kinematics compared with their propensity score-matched counterparts, suggesting that shoulder injury alone may not greatly alter pitching mechanics. However, whereas prior groups have shown a decrease in trunk rotation at foot contact after surgical repair for SLAP tears, our study suggests that this kinematic change may alternatively originate with the injury itself.

CLINICAL RELEVANCE

Understanding the cause of biomechanical adaptations by pitchers after injury can better aid clinicians and coaching staff in providing individualized and specific care to the throwing athlete.

Squatting Throwing Is Not Associated With Increased Medial Elbow Torque in Youth Baseball Catchers

PURPOSE

To compare medial elbow stress during squatting throwing, standing throwing, and maximum effort throwing and to analyze its relationships with throwing variables and the hip joint internal rotation (IR) range of motion (ROM) in youth baseball catchers.

METHODS

Forty-five youth baseball catchers were recruited. Exclusion criteria included pain during throwing, history of surgery, or upper-extremity injuries within 12 months. Catchers performed 5 throws for each of the following throwing conditions: squatting throwing, standing throwing, and maximum effort throwing. Catchers were outfitted with a wearable sensor sleeve that recorded the medial elbow torque, arm speed, and shoulder rotation. Ball velocity was measured using a radar gun.

RESULTS

Final analysis included 42 catchers (mean age, 11.5 ± 1.2 years; mean catcher experience, 16.7 ± 10.3 months). The medial elbow torque was significantly greater during maximum effort throwing (19.0 ± 5.2 Nm) than during squatting throwing (14.3 ± 5.4 Nm) and standing throwing (15.7 ± 4.7 Nm) (both P < .001); there was no significant difference between squatting throwing and standing throwing. Multiple linear regression analysis showed that the ball velocity was significantly positively associated with the medial elbow torque during squatting throwing and standing throwing (P = .023 and P = .029, respectively). During squatting throwing, the hip IR ROM on the throwing side was significantly negatively associated with the medial elbow torque (P = .011).

CONCLUSIONS

The medial elbow torque during squatting throwing was equivalent to that during standing throwing. Increased medial elbow torque was associated with greater ball velocity during squatting throwing and standing throwing and with decreasing hip joint IR ROM on the throwing side during squatting throwing. Evaluation and stretching of the hip joint IR ROM on the throwing side may be important to decrease elbow stress during squatting throwing in youth baseball catchers.

LEVEL OF EVIDENCE

Level II, prospective comparative observational trial.

Increased Elbow and Olecranon Injury History in Professional Pitchers With Increased Elbow Flexion at Ball Release

BACKGROUND

Elbow flexion at late portions of the pitch has been associated with increased elbow varus torque, a kinetic surrogate associated with injury risk. Direct examinations of injury incidence with elbow flexion angles have not been conducted in professional pitchers.

PURPOSE

To compare elbow and shoulder injury incidence among professional baseball players stratified by degree of elbow flexion at ball release (BR).

STUDY DESIGN

Descriptive laboratory study.

METHODS

Professional pitchers (N = 314) were instructed to pitch between 8 and 12 fastballs while being evaluated using motion capture technology. Upper extremity injury incidence was recorded upon interview. Pitchers were subsequently subdivided into 3 groups based on increasing elbow flexion at BR. Analysis of variance was used to compare participant characteristics and kinematic and peak kinetic variables. An odds ratio (OR) was calculated to determine the risk of having a previous upper extremity injury based on the degree of elbow flexion at BR.

RESULTS

A total of 116 pitchers (132 documented injuries) had a previous upper extremity injury, with elbow injury (76 injuries; 57.6%) being the most common. Evaluation of kinetic values showed that pitchers with the smallest elbow flexion at BR had significantly less peak elbow flexion torque than did those with greatest elbow flexion at BR (3.8 ± 0.5 vs 4.1 ± 0.6 %weight × height; P = .003). Pitchers who demonstrated a greater than average degree of elbow flexion at BR when pitching were more likely to have a history of elbow injury (OR, 1.97; 95% CI, 1.14-3.40; P = .015) and olecranon spur formation or stress fracture (OR, 5.79; 95% CI, 1.25-26.85; P = .025).

CONCLUSION

Pitchers with greater elbow flexion at BR had significantly higher odds of previous injury of the elbow and olecranon. Increasing elbow flexion has been shown to place the medial elbow in a position to carry a greater amount of load, which may be exacerbated during the final moments of the pitching motion. Professional pitchers can consider decreasing elbow flexion at BR as a potential, modifiable risk factor for elbow injury, in particular for olecranon spur formation and fracture.

CLINICAL RELEVANCE

This study attempts to associate injury incidence with a modifiable, kinematic variable for an at-risk population.

Pitching Mechanics and the Relationship to Accuracy in Professional Baseball Pitchers

BACKGROUND

Biomechanical predictors of pitching accuracy are underevaluated in baseball research. It is unclear how pitchers with higher accuracy differ in terms of kinematics and upper extremity kinetics.

PURPOSE

To differentiate high- and low-accuracy professional pitchers by full-body kinematic and upper extremity kinetic parameters.

STUDY DESIGN

Descriptive laboratory study.

METHODS

In total, 121 professional baseball pitchers threw 8 to 12 fastballs while assessed with motion-capture technology (480 Hz). Pitchers were divided into high-accuracy (n = 33), moderate-accuracy (n = 52), and low-accuracy (n = 36) groups based on the absolute center deviation of each pitcher's average pitch to the center of the pitching chart by greater or less than 0.5 SD from the mean, respectively. The 95% confidence ellipses with comparisons of major and minor radii and pitching probability density grids were constructed. Analysis of variance was used to compare kinematic and kinetic values between groups.

RESULTS

The absolute center deviation (14.5% ± 6.7% vs 33.5% ± 3.7% grid width; P < .001) was significantly lower in the high-accuracy compared with the low-accuracy group, with no significant difference in ball velocity (38.0 ± 1.7 vs 38.5 ± 2.0 m/s; P = .222). Lead knee flexion at ball release (30.6°± 17.8° vs 40.1°± 16.3°; P = .023) was significantly less for the high-accuracy pitchers. Peak normalized shoulder internal rotation torque (5.5% ± 1.0% vs 4.9% ± 0.7% body weight [BW] × body height [BH]; P = .008), normalized elbow varus torque (5.4% ± 1.0% vs 4.8% ± 0.7% BW × BH; P = .008), and normalized elbow medial force (42.9% ± 7.3% vs 38.6% ± 6.2% BW; P = .024) were significantly greater for the low-accuracy group compared with the high-accuracy group.

CONCLUSION

Professional pitchers with increased accuracy experienced decreased throwing arm kinetics. These pitchers had increased lead knee extension at later stages of the pitch, potentially providing more stable engagement with the ground and transference of kinetic energy to the upper extremities. Professional pitchers can consider increasing lead knee extension at the final stages of the pitch to improve the accuracy of their throws and mitigate elbow varus torque.

CLINICAL RELEVANCE

Increased elbow varus torque, shoulder internal rotation torque, and elbow medial force in less accurate pitchers may contribute to increased injury risk in this group.

Differences in Shoulder Internal Rotation Strength Between Baseball Players With Ulnar Collateral Ligament Reconstruction and Healthy Controls

Background:

Studies have indicated decreased shoulder internal rotation (IR) and external rotation (ER) strength in the throwing limb of baseball players after ulnar collateral ligament injury. There is limited evidence on the recovery of shoulder rotation strength after primary ulnar collateral ligament reconstruction (UCLR).

Hypothesis:

At the time of return to throwing, baseball players who underwent UCLR would demonstrate decreased IR and ER shoulder strength in the throwing arm as compared with healthy baseball players.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

Male competitive high school and collegiate baseball athletes participated in this study. Athletes who underwent UCLR were compared with healthy controls who were matched by age, height, weight, and position. Bilateral isometric shoulder ER and IR strength was measured using a handheld dynamometer for all participants at the time of initial evaluation (UCLR group) and throughout the course of a season (healthy group). Independent t tests were run to calculate mean differences in ER and IR shoulder strength between the groups, with significance set at P < .05.

Results:

A total of 86 baseball athletes participated in this study (43 UCLR group, 43 healthy group). At the time of return to throwing (mean ± SD, 194 ± 30 days postoperatively), the 2 groups demonstrated no significant differences in nonthrowing arm ER or IR strength (P = .143 and .994, respectively). No significant difference was found between groups for throwing arm ER strength (P = .921); however, the UCLR group demonstrated significantly less throwing arm IR strength than the healthy group (144.2 ± 27.8 vs 157.6 ± 27.1 N; P = .023).

Conclusion:

The results of this study demonstrate that throwing arm rotator cuff strength may not fully recover before the initiation of a return-to-throwing program after UCLR. These data provide a potential framework for clinicians to assist in the management and exercise prescription of the baseball athlete after UCLR and before medical release and the initiation of a return-to-throwing program.

Biomechanical Analysis of the Throwing Athlete and Its Impact on Return to Sport

Throwing sports remain a popular pastime and frequent source of musculoskeletal injuries, particularly those involving the shoulder and elbow. Biomechanical analyses of throwing athletes have identified pathomechanic factors that predispose throwers to injury or poor performance. These factors, or key performance indicators, are an ongoing topic of research, with the goals of improved injury prediction, prevention, and rehabilitation. Important key performance indicators in the literature to date include shoulder and elbow torque, shoulder rotation, kinetic chain function (as measured by trunk rotation timing and hip-shoulder separation), and lower-extremity mechanics (including stride characteristics). The current gold standard for biomechanical analysis of the throwing athlete involves marker-based 3-dimensional) video motion capture. Emerging technologies such as marker-less motion capture, wearable technology, and machine learning have the potential to further refine our understanding. This review will discuss the biomechanics of throwing, with particular attention to baseball pitching, while also delineating methods of modern throwing analysis, implications for clinical orthopaedic practice, and future areas of research interest.

Level of Evidence

V, expert opinion.

Machine Learning and Statistical Prediction of Pitching Arm Kinetics

BACKGROUND

Over the past decade, research has attempted to elucidate the cause of throwing-related injuries in the baseball athlete. However, when considering the entire kinetic chain, full body mechanics, and pitching cycle sequencing, there are hundreds of variables that could influence throwing arm health, and there is a lack of quality investigations evaluating the relationship and influence of multiple variables on arm stress.

PURPOSE

To identify which variables have the most influence on elbow valgus torque and shoulder distraction force using a statistical model and a machine learning approach.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A retrospective review was performed on baseball pitchers who underwent biomechanical evaluation at the university biomechanics laboratory. Regression models and 4 machine learning models were created for both elbow valgus torque and shoulder distraction force. All models utilized the same predictor variables, which included pitch velocity and 17 pitching mechanics.

RESULTS

The analysis included a total of 168 high school and collegiate pitchers with a mean age of 16.7 years (SD, 3.2 years) and BMI of 24.4 (SD, 1.2). For both elbow valgus torque and shoulder distraction force, the gradient boosting machine models demonstrated the smallest root mean square errors and the most precise calibrations compared with all other models. The gradient boosting model for elbow valgus torque reported the highest influence for pitch velocity (relative influence, 28.4), with 5 mechanical variables also having significant influence. The gradient boosting model for shoulder distraction force reported the highest influence for pitch velocity (relative influence, 20.4), with 6 mechanical variables also having significant influence.

CONCLUSION

The gradient boosting machine learning model demonstrated the best overall predictive performance for both elbow valgus torque and shoulder distraction force. Pitch velocity was the most influential variable in both models. However, both models also revealed that pitching mechanics, including maximum humeral rotation velocity, shoulder abduction at foot strike, and maximum shoulder external rotation, significantly influenced both elbow and shoulder stress.

CLINICAL RELEVANCE

The results of this study can be used to inform players, coaches, and clinicians on specific mechanical variables that may be optimized to mitigate elbow or shoulder stress that could lead to throwing-related injury.

Elbow varus torque and ball velocity associations in high school and professional pitchers with increased sagittal-plane trunk tilt

BACKGROUND

Increased sagittal-plane trunk tilt is thought to increase drive in the anterior direction toward home plate, transferring energy from the trunk to the distal upper extremity, ultimately generating greater ball velocity. Increased sagittal trunk tilt has also been implicated in the risk of upper-extremity joint loading in baseball pitchers by way of elbow varus torque (EVT), a metric previously associated with elbow injury in professional pitchers. The purposes of this study were (1) to compare sagittal trunk tilt positioning between high school and professional pitchers throughout the pitch and (2) to identify the potential associations between sagittal-plane trunk tilt, ball velocity, and EVT for both cohorts.

METHODS

Professional and high school pitchers were instructed to throw fastballs while being evaluated with 3-dimensional motion capture (480 Hz). Sagittal trunk tilt motion throughout the pitching motion was compared between cohorts from maximum knee height to maximum shoulder internal rotation. To assess the effects of sagittal-plane trunk tilt on ball velocity and EVT, linear mixed-effect models were created.

RESULTS

Professional pitchers (n = 100, 882 pitches) achieved greater sagittal trunk tilt than high school pitchers (n = 57, 519 pitches) during early portions of the pitching motion, including maximum positive sagittal trunk tilt (46.6° ± 8.3° vs. 43.6° ± 10.2°, P = .042). Professional pitchers also had greater sagittal trunk tilt excursion throughout the pitch motion (68.0° ± 11.4° vs. 62.5° ± 11.0°, P = .004). For every 10° increase in sagittal trunk tilt at ball release for professional pitchers, ball velocity increased by 0.36 m/s (B = 0.036 and β = 0.194, P < .001) or 0.9% average ball velocity whereas EVT increased by 0.14% body weight × body height (B = 0.014 and β = 0.159, P < .001) or 2.9% average normalized EVT. For every 10° increase in sagittal trunk tilt at ball release for high school pitchers, ball velocity increased by 0.34 m/s (B = 0.097 and β = 0.025, P = .025) or 1.1% average ball velocity whereas EVT increased by 0.07% body weight × body height (B = 0.007 and β = 0.086, P = .016) or 1.7% average normalized EVT.

CONCLUSION

Increased positive sagittal-plane trunk tilt was significantly associated with greater ball velocity and increased EVT for both professional and high school pitchers. Peak EVT estimates were consistently more pronounced than ball velocity benefits for both populations, suggesting that no specific time point may provide a ball velocity benefit while concomitantly minimizing EVT. Both professional and high school pitchers should consider this trade-off, which may influence injury risk, when engaging in higher degrees of positive sagittal-plane trunk tilt.

Elbow Torque May be Predictive of Anatomic Adaptations to the Elbow After a Season of Collegiate Pitching: A Dynamic Ultrasound Study

Purpose

To determine whether elbow torque was associated with anatomic adaptations of the medial elbow following a season of competitive pitching.

Methods

Pitchers from 3 collegiate baseball teams were recruited during the preseason for participation. Before the season, pitchers were recorded throwing 5 “game-speed” fastball pitches from a standard distance off a mound while wearing a wearable sensor baseball compression sleeve that calculates elbow torque, arm speed, arm slot, and arm rotation. Participants subsequently underwent dynamic ultrasound imaging of the medial elbow, including measurements of the ulnar collateral ligament (UCL) and ulnohumeral joint space to assess elbow laxity. Following a full season of competitive pitching, all testing was repeated, and statistical analysis comparing preseason to postseason sonographic findings was performed.

Results

Twenty-eight collegiate pitchers underwent preseason sonographic and kinematic testing. Nineteen pitchers were available for postseason testing. The average age (standard deviation) and playing experience was 19.9 (1.2) and 14.7 (1.5) years. Compared with preseason, there were significant increases in postseason UCL thickness (1.92 ± 0.09 vs 1.56 ± 0.09 mm, P < .01) and elbow laxity (1.77 ± 0.23 vs 1.15 ± 0.22 mm, P = .028) after a season of pitching. No significant changes in pitching kinematic measurements were observed between preseason and postseason testing. Preseason pitching kinematic measurements were significantly associated with increased UCL thickness (arm slot: beta estimate –0.03 ± 0.01, P = .011) and reduction in elbow laxity (elbow torque: beta estimate –0.03 ± 0.01, P = .04) after a season of pitching. Pitchers with increased body weight and arm length demonstrated reduced medial elbow torque during pitching (P < .05).

Conclusions

After a season of competitive pitching, adaptive changes of the medial elbow were demonstrated on dynamic ultrasound. However, the influence of pitching kinematic measurements on these adaptations are of small magnitude and unknown clinical significance. Although wearable sensor technology may have value in trending individual pitcher kinematics, no discrete threshold appears to predict the development of adaptive changes at the elbow.

Level of Evidence

Level II, prospective observational study.

Comparison of OnBaseU Tests with Biomechanical Motion Analysis in Youth Baseball Pitchers

BACKGROUND

The OnBaseU screen was developed to evaluate a baseball pitcher's ability to perform movement patterns key to pitching. However, due to lack of validation, it is unclear what application is ideal for this screen.

PURPOSE

To compare four OnBaseU tests to relevant pitching mechanics measured using 3D motion capture to evaluate if the OnBaseU screen can be used to assess pitching mechanics. The secondary purpose was to compare OnBaseU and 3D motion capture seated trunk rotation test results to determine the validity of the OnBaseU test.

METHODS

OnBaseU screening and 3D motion capture pitching evaluations were completed for 103 adolescent pitchers (age = 15.2 ± 1.29 years; height = 1.80 ± 0.0866 m; weight = 76.2 ± 13.8 kg). A motion capture seated trunk rotation test was also conducted on 80 of the 103 youth players (age = 15.2 ± 1.32 years; height = 1.80 ± 0.0889 m; weight = 75.7 ± 13.9 kg).

RESULTS

Stride length and OnBaseU side step walkout test data were moderately correlated, and all other comparisons were not correlated or were minorly correlated. No significant differences were found between kinematics from players who obtained different OnBaseU scores, except for stride lengths during pitching of players who scored a 1 or 3 on the OnBaseU side step walkout test (p<0.01). Further, OnBaseU and motion capture seated trunk rotation tests were not correlated (r = 0.003) and not found to be statistically associated (p = 0.83).

CONCLUSION

Results from this study indicate that the OnBaseU clinical assessment screen may not have use in assessing pitching mechanics and that visual grading criteria used in the OnBaseU seated trunk rotation test may not be accurate.

LEVEL OF EVIDENCE

3.

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.

Individualised Ball Speed Prediction in Baseball Pitching Based on IMU Data

Ball velocity is considered an important performance measure in baseball pitching. Proper pitching mechanics play an important role in both maximising ball velocity and injury-free participation of baseball pitchers. However, an individual pitcher’s characteristics display individuality and may contribute to velocity imparted to the ball. The aim of this study is to predict ball velocity in baseball pitching, such that prediction is tailored to the individual pitcher, and to investigate the added value of the individuality to predictive performance. Twenty-five youth baseball pitchers, members of a national youth baseball team and six baseball academies in The Netherlands, performed ten baseball pitches with maximal effort. The angular velocity of pelvis and trunk were measured with IMU sensors placed on pelvis and sternum, while the ball velocity was measured with a radar gun. We develop three Bayesian regression models with different predictors which were subsequently evaluated based on predictive performance. We found that pitcher’s height adds value to ball velocity prediction based on body segment rotation. The developed method provides a feasible and affordable method for ball velocity prediction in baseball pitching.

Baseball Pitching Arm 3-D Inertial Parameter Calculations from Body Composition Imaging and a Novel Overweight Measure for Youth Pitching Arm Kinetics

Many baseball pitching studies have used inverse dynamics to assess throwing arm kinetics as high and repetitive kinetics are thought to be linked to pitching injuries. However, prior studies have not used participant-specific body segment inertial parameters (BSIPs) which are thought to improve analysis of high-acceleration motions and overweight participants. This study's objectives were to 1) calculate participant-specific BSIPs using DXA measures, 2) compare inverse dynamic calculations of kinetics determined by DXA-calculated BSIPs (full DXA-driven inverse dynamics) against kinetics using the standard inverse dynamics approach with scaled BSIPs (scaled inverse dynamics), and 3) examine associations between full DXA-driven kinetics and overweight indices: body mass index (BMI) and segment mass index (SMI). Eighteen participants (10-11 years old) threw 10 fastballs that were recorded for motion analysis. DXA scans were used to calculate participant-specific BSIPs (mass, center of mass, radii of gyration) for each pitching arm segment (upper arm, forearm, hand), BMI, and SMI. The hypotheses were addressed with t-tests and linear regression analyses. The major results were that 1) DXA-calculated BSIPs differed from scaled BSIPs for each pitching arm segment, 2) calculations for shoulder, but not elbow, kinetics differed between the full DXA-driven and scaled inverse dynamics analyses, and 3) full DXA-driven inverse dynamics calculations for shoulder kinetics were more strongly associated with SMI than with BMI. Results suggest that using participant-specific BSIPs and pitching arm SMIs may improve evidence-based injury prevention guidelines for youth pitchers.

Association Between Passive Hip Range of Motion and Pitching Kinematics in High School Baseball Pitchers

BACKGROUND

Limitations in passive hip range of motion (PROM) may negatively affect pitching mechanics in baseball pitchers. Understanding the relationships between PROM and mechanics can assist in the development of injury prevention protocols.

PURPOSE

The purpose of this study was to examine the association of hip rotational PROM with pelvis and trunk rotation during pitching in high school baseball pitchers. Study Design: Cross-sectional.

METHODS

Twenty-five healthy high school baseball pitchers volunteered (15.9 ± 1.1 years; 180.4 ± 5.5 cm; 75.4 ± 9.3 kg). Seated passive hip internal rotation (IR) and external rotation (ER) PROM were measured using a digital inclinometer. Total PROM was calculated (IR+ER). Pitching biomechanical data were collected with a 3-dimensional electromagnetic tracking system while pitchers threw fastballs. Simple linear regressions were performed to examine the association between hip IR, ER, and total PROM with pitching kinematics at foot contact including stride length, pelvis rotation, and trunk rotation.

RESULTS

Only one significant association in PROM and kinematics was observed. Drive leg hip IR PROM was associated with trunk rotation angle [F(1,24) = 4.936, p = 0.036], with an R2 = 0.177. Drive leg total PROM was not associated trunk rotation angle [F(1,24) = 4.144, p = 0.053] with an R2 = 0.153.

CONCLUSIONS

Increased drive leg hip IR PROM was associated with decreased trunk rotation towards home plate. Hip total PROM and ER were not related to pitching mechanics.

LEVEL OF EVIDENCE

2.

Does Velocity Increase From Flat-Ground to Mound Work During a Lighter Baseball Training Program?

INTRODUCTION

There has been recent interest in throwing from flat-ground versus the mound regarding stress on the elbow. Typical throwing progression programs begin with flat-ground work and progress to mound work.

METHODS

All baseball pitchers of ages 10 to 17 years who completed a 15-week pitching mechanics and velocity-training program were included. Players' pitch velocity was tested at four time points during training. Average velocity and maximum velocity of pitches from flat-ground were compared with those of mound, and change in velocity between testing sessions was also compared.

RESULTS

Thirty-six male pitchers (average age: 14.4 ± 1.6 years) were included. Fastball velocity increased by an average of 5.2 mph (95% confidence intervals 2.0 to 8.8 mph) at the end of the training program. When change in average and maximum velocity was compared between the four testing sessions, the most notable increase in velocity occurred between the third and fourth testing sessions. Both sessions were thrown from the mound.

CONCLUSION

The 15-week baseball pitcher-training program markedly improved pitching velocity. Throwing from a mound compared with flat-ground resulted in the largest velocity increase. Therefore, when attempting to increase a pitcher's velocity, throwing from the mound should be an integral part of any velocity program.

Are Wearable Sensors Valid and Reliable for Studying the Baseball Pitching Motion? An Independent Comparison With Marker-Based Motion Capture

BACKGROUND

In recent years, the prevalence of medial ulnar collateral ligament injuries has increased in throwers of all ages and skill levels. The motusBASEBALL sensor possesses an inertial measurement unit (IMU) that has been developed and applied to the throwing arm to allow for measurements of several objective parameters, which may prove beneficial for monitoring, rehabilitation, and injury prevention in the throwing athlete. However, the reliability, consistency, and validity of the IMU have not been independently assessed.

PURPOSE

To evaluate the reliability, consistency, and validity of the motusBASEBALL sensor compared with the historic gold standard of marker-based motion capture.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 10 healthy male baseball athletes with varsity-level high school experience volunteered to participate in this study. Participants were fitted with 37 retroreflective markers for motion capture and the motusBASEBALL IMU sensor. Participants threw 5 fastballs at maximum effort, with measurements recorded simultaneously by motion capture and the IMU. Arm slot, arm speed, arm stress, and shoulder rotation were measured and compared.

RESULTS

Of the 4 metrics generated by the IMU, significant differences were found for 3 of the throwing metrics compared with motion capture including arm slot (5.0°± 6.1°; P = .037), elbow varus torque (9.4 ± 12.0 N·m; P = .037), and shoulder rotation (6.3°± 6.1°; P = .014). Arm speed did not demonstrate a statistically significant difference (29.2 ± 96.8 rpm; P = .375). The IMU consistently underreported pitching performance values. Shoulder rotation exhibited excellent reliability with <5° of error, and arm slot demonstrated good reliability with <10° of error. Arm stress and arm speed were less reliable.

CONCLUSION

The IMU was not accurate or valid for arm slot, arm stress, and shoulder rotation compared with marker-based motion capture. It was relatively accurate for arm speed. Despite its lack of validity, it was consistent and reliable for arm speed and shoulder rotation and relatively reliable for arm slot and arm stress. Caution should be used when comparing values provided by this IMU to the gold standard of marker-based motion capture.

CLINICAL RELEVANCE

IMU technology has potential to be used in monitoring, rehabilitation, and injury prevention in throwing athletes if valid. This study demonstrates that the values provided by the IMU should not be considered equivalent to those generated by the gold standard of marker-based motion capture; however, there may still be a role for this technology when relying on its internal consistency for intrathrower comparisons and tracking.

Increased Upper Arm Length and Loading Rate Identified as Potential Risk Factors for Injury in Youth Baseball Pitchers

BACKGROUND

In the throwing elbow, increased elbow torque has been correlated with increased injury risk. Additional insight into the relationships between anthropometric factors and elbow joint loading is warranted.

PURPOSE

To investigate the relationship among physical limb length characteristics, elbow kinetics, and elbow kinematics in youth baseball pitchers and to examine the relationship between elbow varus loading rate and elbow kinetics.

DESIGN

Descriptive laboratory study.

METHODS

A total of 27 male youth baseball pitchers participated (mean ± SD: age, 15.8 ± 2.7 years; height, 176.3 ± 13.0 cm; weight, 71.7 ± 16.4 kg). Upper arm (UA) and forearm (FA) lengths were measured using a moveable sensor to digitize bony landmarks. Kinematic data were collected at 240 Hz using an electromagnetic tracking system. Participants threw 3 fastballs to a catcher at a regulation distance (60 ft 6 in), and the fastest velocity trial was used for analysis. Linear regression was used to determine the relationship among limb length characteristics, elbow kinetics, and elbow kinematics after accounting for the effects of body weight and height.

RESULTS

Pitchers with longer UA length experienced increased maximum elbow varus torque (P = .005) and maximum net elbow force (P = .001). Pitchers with an increased forearm to UA ratio had decreased elbow compression force (P < .001) and exhibited a more flexed elbow at foot contact (P = .001). Pitchers with greater maximum loading rates experienced greater elbow varus torque (P = .002).

CONCLUSION

In youth baseball pitchers, longer UA length and greater loading rate increase varus torque about the elbow during a fastball pitch.

CLINICAL RELEVANCE

Longer UA length and greater loading rate may place pitchers at risk of injury because of their relationship with kinetic values.