The effect of pitching biomechanics on the upper extremity in youth and adolescent baseball pitchers

Effects of Shoulder Corrective Training Program on Pitching Loads and Sonographic Morphology in Elbow Joint in Youth Baseball Players

ABSTRACT

Chen, P-T, Lin, Y-C, Chang, H-Y, Chiu, C-H, Chen, C-Y, Chen, P, and Lin, Y-H. Effects of shoulder corrective training program on pitching loads and sonographic morphology in elbow joint in youth baseball players. J Strength Cond Res 38(8): e440-e447, 2024-We assessed the effects of a 12-week shoulder corrective training program for shoulder flexibility and strengthening on pitching loads and sonographic morphology of the elbow joints in youth baseball players. Seventeen subjects were recruited and underwent evaluations before and after the training program. We found that following training, subjects demonstrated significantly increased ranges of shoulder internal rotation (38.9 ± 12.9° vs. 69.2 ± 10.8°, p < 0.001), external rotation (91.2 ± 14.6° vs. 107.3 ± 9.5°, p = 0.004), and horizontal adduction (21.5 ± 8.0° vs. 32.7 ± 7.3°, p = 0.002); improved strength in the shoulder internal rotators (8.7 ± 1.6 kg vs. 9.8 ± 2.1 kg, p = 0.04), external rotators (6.5 ± 1.9 kg vs. 7.5 ± 2.8 kg, p = 0.04), middle trapezius (12.7 ± 2.1 kg vs. 14.3 ± 2.4 kg, p = 0.04), and middle deltoid muscles (10.8 ± 3.3 kg vs. 14.8 ± 3.2 kg, p = 0.001); and decreased thickness of the ulnar collateral ligament (6.1 ± 0.6 mm vs. 4.8 ± 0.7 mm, p = 0.002). Although there was no substantial change in elbow torque and arm speed, significantly increased ball speed (51.2 ± 4.6 mph vs. 54.1 ± 4.5 mph, p < 0.001) and decreased arm slot (63.8 ± 11.9° vs. 53.0 ± 12.7°, p = 0.02) were observed. We suggest that adequate corrective training should be performed regularly to minimize or mitigate adverse soft tissue changes at the elbow in youth baseball players. Balanced shoulder strength and flexibility may decrease medial elbow stress during pitching. Future studies should consider the kinetic and kinematic effects of other corrective training programs on the shoulder or elbow joint during pitching.

A narrative review of little league shoulder: proximal humeral physis widening is only one piece of the puzzle, it is time to consider posterior glenoid dysplasia

Baseball athletes across all levels of play are at an increased risk for upper extremity injury due to the supraphysiologic demands on the shoulder and elbow during overhead throwing. Little league baseball players present with a unique subset of injuries that can affect the growth plate, commonly at the shoulder or the elbow. Ascertaining a diagnosis and plan of care for little league shoulder (LLS) historically focuses on the proximal humeral physis in skeletally immature throwing athletes presenting with shoulder pain. However, while not a current standard of care, posterior glenoid dysplasia is often present in youth baseball athletes presenting with LLS, warranting a shift in the way clinicians evaluate for and treat the youth baseball athlete's pathologic shoulder. Therefore, purpose of this narrative review is 2-fold: first, to describe the current standard of care as it relates to a diagnosis of LLS, and second, to critically describe a comprehensive evaluation process for youth throwing athletes with shoulder pain that includes screening for evidence of posterior glenoid dysplasia. This paper summarizes the current state of the available evidence for anatomic considerations of LLS in the baseball athletes throwing shoulder. Additionally, we provide a framework for clinical evaluation using a multidisciplinary approach to evaluate the entire kinetic chain of the youth baseball athlete presenting with LLS and posterior glenoid dysplasia. A case study is presented to describe common presentations, clinical and objective examinations, and a plan of care from time of evaluation to return to throwing.

Biomechanical effects of foot placement during pitching

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

Characteristics and Clinical Assessment of Elbow Pain in Youth Baseball Players

Elbow injuries related to the throwing motion in baseball during the growth period present difficulties for early detection and may cause serious future disabilities. This study aimed to comprehensively determine the characteristics and clinical assessment of elbow pain in youth baseball players. Two hundred and sixteen young baseball players underwent elbow medical examination. Basic information and physical examination, clinical assessment, and ultrasonography results were examined. Univariate analyses were statistically performed between the pain-free (98 participants) and elbow pain (118 participants) groups. The mean age was 11.6 years, and ultrasonographic abnormalities were found on the medial side of the elbow in 37.5%. In total, 118 (54.6%) participants experienced elbow pain, with 64.4% of them complaining of elbow pain on the medial side. Players with multiple positions (≥2 positions) had a significantly higher prevalence of elbow pain. Height, weight, length of baseball experience, and positive rates of horizontal flexion and moving valgus stress tests were higher in the elbow pain group than in the pain-free group. The risk factors and clinical assessment for elbow pain are useful for the prevention and early detection of throwing elbow injuries in youth baseball players.

Evolution of the throwing shoulder: why apes don't throw well and how that applies to throwing athletes

BACKGROUND

Humans have unique characteristics making us the only primate that can throw well while most other primates throw predominately underhand with poor speed and accuracy. The purpose of this study is to illuminate the uniquely human characteristics that allow us to throw so well. When treating an injury such as a labral tear or capsule tear, this study hopes the reader can gain a better understanding of the issues that lead to the tear and those that may determine the success of treatment besides the actual repair.

METHODS

In addition to a review of scientific and medical literature, information was obtained from interviews and experience with primate veterinarians, anthropologists, archeologists, and professional baseball players. These sources were used to study the connection between evolutionary throwing activities and current sports medicine issues.

RESULTS

Arm acceleration requires a functional kinetic chain, rapid motor sequences, and the ability to absorb elastic energy in the shoulder. Successful treatment of the throwing shoulder requires awareness of the shoulder's position in the kinetic chain and correction of defects in the ability to execute the kinetic chain. Some problems in the shoulder could reflect regression to a more primitive anatomy or dyskinesis. Return of performance requires regaining the elasticity in the tissues of the shoulder to temporarily store kinetic energy. For example, tissue remodeling after rotator cuff repair continues for months to years; however, the newly formed tissue lacks the same elasticity of the native tendon. This suggests why throwing performance typically does not return for 7 or more months after repair even though there may be structural integrity at 3-4 months.

CONCLUSION

The shoulder has developed uniquely in modern man for the act of throwing. The anatomic deficiencies in primates for throwing provide an illustration of the more subtle changes that a throwing athlete might have that are detrimental to throwing. Nonhuman primates have been unable to demonstrate the kinetic chain sequence for throwing secondary to the lack of neurologic pathways required. Humans are more sophisticated and precise in their movements but lack robusticity in their bone and muscle architecture, seen especially in the human rotator cuff. Successful treatment of a throwing injury requires familiarity with the conditions that cause the injury or affect the rehabilitation process. The return of performance following injury or surgery requires regaining the elasticity in the tissues of the shoulder to temporarily store kinetic energy from the kinetic chain.

History of Ulnar Collateral Ligament Injury and College Pitcher Fastball Profiles: A Retrospective, Observational, Live Pitching Analysis

PURPOSE

The aim of this study was to retrospectively compare the fastball profiles of pitchers who had previously sustained grade I or II ulnar collateral ligament (UCL) injuries, were rehabilitated, and released back for competition with those of pitchers with no history of elbow injury.

METHODS

Eighteen pitchers from the pitching staff of 1 National Collegiate Athletic Association Division III team participated in this study. Group 1 had a history of grade I or II UCL injury (n = 8), and group 2 (n = 10) did not. A computerized pitch tracking device was used to analyze ball movement and pitching mechanics. The hypothesis was that the pitchers with a history of injury (group 1) would display differing fastball velocity-ball movement relationships compared to those without (group 2).

RESULTS

The groups had similar heights, weights, pitching experiences, and arm slot positions at ball release. The pitching coach-determined preinjury arm slot position and the postinjury computerized pitch tracking device measurements after return to competition displayed strong agreement (r = 0.83), suggesting comparable pre and postinjury pitching techniques. The groups had comparable glenohumeral joint range of motion and fastball profiles, except that group 1 released the ball at a 2.5 times lesser horizontal distance away from the pitching rubber center. Group 2 also displayed consistently more robust and more frequent fastball movement relationships with velocity, horizontal break, and vertical break than group 1.

CONCLUSIONS

Reduced horizontal ball release distances at comparable vertical ball release heights without changes in the arm slot position suggest that pitchers with a history of grade I or II UCL injury have greater contralateral trunk tilt and elbow flexion at ball release. Increased contralateral trunk tilt may occur to increase pitch velocity at the expense of ball movement while placing the pitching elbow in a potentially injurious position. Computerized fastball profile analysis using a computerized pitch tracking device, in conjunction with coach pitching technique observation, and team medical staff clinical examination may help better identify pitchers with an increased risk of UCL injury.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic II.

Feasibility of the pitch efficiency rating: A novel tool for systematic assessment of pitching mechanics in developing throwing athletes

BACKGROUND

Injuries in younger baseball athletes continue to increase despite work characterizing risk factors. Three-dimensional (3D) motion capture may identify suboptimal pitching mechanics that predispose an athlete to injury, but 3D-motion analysis is often inaccessible. Thus, there is a gap between the current biomechanics literature and its practical application in young athletes. The current study aims to assess the reliability of the pitch efficiency rating (PER) as a systematic tool to evaluate throwing mechanics in developing baseball pitchers.

OBJECTIVE

To determine the feasibility of application and reliability of a novel, scientifically informed tool (PER) for the assessment of pitching mechanics.

DESIGN

Reliability study using Bland-Altman methods for assessing agreement between two raters.

SETTING

Academic medical center through community outreach.

PARTICIPANTS

Pitching mechanics were assessed and rated with the PER for 40 athletes (26 high school, 14 Division III), average age 19.0 years old (range 15.3-23.7 years old).

INTERVENTIONS

N/A.

MAIN OUTCOME MEASURES

Interrater and intrarater reliability as calculated by intraclass correlation coefficient (ICC).

RESULTS

For initial readings comparing interrater reliability between Rater 1 and Rater 2, the ICC was calculated at 0.80 (95% confidence interval [CI] 0.66-0.89) and 0.76 (95% CI 0.60-0.86) for the second set of ratings. Regarding intrarater reliability across reads, ICC was found to be 0.63 (95% CI 0.43-0.79) for Rater 1, and 0.91 for Rater 2 (95% CI 0.85-0.95).

CONCLUSIONS

The present study introduces the PER as a potential tool for evaluating pitching mechanics. However, the intrarater reliability of the PER did not meet preestablished criteria in one of the two pilot raters. Further study is needed to continue to assess the reliability of the tool across diverse demographics.

Relationship between shoulder and elbow range of motion and ultrasonographic structural abnormalities in the elbow of Taiwanese high school baseball players

BACKGROUND

Ultrasonographic structural abnormalities are regarded as one of the risk factors of elbow injuries. Elbow injuries are commonly associated with decreased shoulder/elbow range of motion (ROM). The purpose of this study is to determine the relationship between shoulder/elbow ROM and elbow ultrasonographic structural abnormalities in Taiwan high school baseball players.

METHODS

A total of 533 Taiwan high school baseball players were enrolled. Physical examinations including measurements on shoulder/elbow ROM and elbow sonographic examinations were performed and recorded by professional physicians. The analyses were conducted in three subgroups according to their defensive position because the training programs were different. All players pooled, pitchers-only, and fielders-only, due to several demographic differences among these subgroups. In all the subgroups, univariate analyses were conducted separately for participants with and those without elbow ultrasonographic structural abnormalities, and then multivariate analyses were conducted to identify factors significantly related. The odds ratios (ORs) were used to estimate the risk of elbow ultrasonographic structural abnormalities.

RESULTS

Demographic data showed that pitchers had taller body height (P < 0.001) and greater elbow flexion/extension ROM (P < 0.001). When all players were pooled, significant risk factors included started playing baseball at an younger age (OR = 1.202; 95% CI = 1.064-1.357; P = 0.003), longer experience of official baseball (OR = 1.154; 95% CI = 1.038-1.283; P = 0.008), lower total shoulder rotation angle (OR = 1.007; 95% CI = 1.000-1.014; P = 0.050), and less total elbow arm angle (OR = 1.052; 95% CI = 1.017-1.088; P = 0.003) For pitchers, significant risk factors included longer experience of official baseball (OR = 1.342; 95% CI = 1.098-1.640; P = 0.004), lower total shoulder rotation angle (OR = 1.016; 95% CI = 1.004-1.027; P = 0.006), and lower total elbow arm angle (OR = 1.075; 95% CI = 1.024-1.129; P = 0.004) (Table 5). There were no significant risk factors for elbow structural abnormalities in fielders.

CONCLUSION

For Taiwan high school pitchers, longer official baseball experience, decreased shoulder total rotational angle, and decreased elbow total flexion/extension angle, were related to ultrasonographic structural abnormalities in elbows.

Rehabilitation of the painful elbow

Although lateral elbow pain and medial ulnar collateral ligament injury are common musculoskeletal pathologies in overhead athletes, the evidence supporting specific interventions for managing these conditions is scarce. Management of these conditions has been guided mostly by expert opinion rather than empirical evidence, yet the lack of comparative data in the literature has not negatively affected return-to-play rates following surgery. However, an understanding of what is known regarding unimodal and multimodal treatments for lateral elbow pain and medial ulnar collateral ligament injury is needed for clinicians to select evidence-based treatment pathways and highlight what is not known to develop future high-quality investigations.

Adaptive pathology: new insights into the physical examination and imaging of the thrower's shoulder and elbow

Throwing with high velocity requires extremes of glenohumeral external rotation of the abducted arm where particularly high forces in the shoulder and elbow are endured. Repeated throwing leads to dominant-arm bony remodeling of the humerus, glenoid, and elbow, and multiple soft tissue changes that would be considered abnormal. Many of these features are thought to be adaptive and protective. The purpose of this work is to (1) define the concept of adaptive pathology; (2) review the mechanics of the throwing motion; (3) review pertinent physical examination and imaging findings seen in asymptomatic throwers' shoulders and elbows and describe how these changes develop and may be adaptive-allowing the thrower to perform at high levels; and then (4) review the principles of surgical treatment in the throwing athletes, which should focus on reducing symptoms, but not necessarily restoring the thrower's anatomy to normal.

Association of Head-Neck Rotation With History of Pitching-Related Elbow Pain in Youth Baseball Players

Background

Prevention of pitching-related elbow pain in youth baseball players is important. Overhead pitching involves a whole-body motion, including head-neck rotation. A limited range of motion of head-neck rotation may cause inefficient pitching motion; however, this association is unclear.

Purpose

To determine whether the range of motion of head-neck rotation is associated with the history of pitching-related elbow pain in youth baseball players.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

A total of 311 youth baseball players were selected and asked to complete a questionnaire survey about their age, weight, height, sex, baseball experience, main position, pitching side, and previous/current elbow pain during pitching. The range of motion of the upper and lower limb joints, head-neck rotation, and thoracic kyphosis angle were measured. Binomial logistic regression analysis was used to identify factors associated with the history of elbow pain related to pitching.

Results

There were 101 players with a history of pitching-related elbow pain (history group) and 142 players with no pitching-related elbow pain (no-history group). The history group had significantly lower values than the no-history group regarding the range of motion of head-neck rotation on the nondominant side (74.9°± 9° vs 77.7°± 9.6°; P = .02) and overall head-neck rotation (150.6°± 14.7° vs 154.9°± 18.4°; P = .04). Binomial logistic regression analysis identified head-neck rotation on the nondominant side (odds ratio [OR], 0.97 [95% CI, 0.94-1.00]), shoulder horizontal adduction on the dominant side (OR, 0.98 [95% CI, 0.96-1.00]), height (OR, 1.04 [95% CI, 1.00-1.08]), and playing position (pitcher) (OR, 0.40 [95% CI, 0.21-0.76]) as factors associated with a history of pitching-related elbow pain.

Conclusion

Our cross-sectional analysis demonstrated that youth baseball players with a history of pitching-related elbow pain had limited head-neck rotation range of motion on the nondominant side, and this was a significant factor associated with the history of pitching-related elbow pain.

Evaluation of Hip Characteristics in Baseball and Softball Athletes with and Without Throwing Arm Pain

During throwing, the lower extremity assists in the generation and transfer of momentum. Lower extremity stability assists in this transfer by providing a base for distal mobility of the arm segments. This study aimed to determine differences between hip rotational range of motion and strength based on the presence of throwing-arm pain (yes/no) and throwing sport (baseball/softball). We hypothesized those experiencing pain would display decreases in hip range of motion and strength, and that softball players would display greater range of motion than baseball, but less strength based on sex-specific characteristics. Forty-four baseball (13±2 years, 165.2±13.0 cm, 58.5±13.4 kg) and 50 softball players (13±2 years, 160.9±11.2 cm, 62.7±17.9 kg) participated. Multivariate analysis of variance tests (2×2) determined differences in bilateral hip range of motion, total arc of motion, and strength between pain status and sport. There were no significant interactions (>0.05) for pain status and sport on hip range of motion, total arc of motion, and strength. Furthermore, no significant main effects (>0.05) were found for pain status or sport alone on range of motion or strength. Future work should be directed at explaining the effects of hip characteristics on the throwing motion and how it equates to throwing-arm health.

Machine Learning Approach for Pitch Type Classification Based on Pelvis and Trunk Kinematics Captured with Wearable Sensors

The large stream of data from wearable devices integrated with sports routines has changed the traditional approach to athletes' training and performance monitoring. However, one of the challenges of data-driven training is to provide actionable insights tailored to individual training optimization. In baseball, the pitching mechanics and pitch type play an essential role in pitchers' performance and injury risk management. The optimal manipulation of kinematic and temporal parameters within the kinetic chain can improve the pitcher's chances of success and discourage the batter's anticipation of a particular pitch type. Therefore, the aim of this study was to provide a machine learning approach to pitch type classification based on pelvis and trunk peak angular velocity and their separation time recorded using wearable sensors (PITCHPERFECT). The Naive Bayes algorithm showed the best performance in the binary classification task and so did Random Forest in the multiclass classification task. The accuracy of Fastball classification was 71%, whilst the accuracy of the classification of three different pitch types was 61.3%. The outcomes of this study demonstrated the potential for the utilization of wearables in baseball pitching. The automatic detection of pitch types based on pelvis and trunk kinematics may provide actionable insight into pitching performance during training for pitchers of various levels of play.

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.

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.

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.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

Forearm Flexor Tendon Injury in Adolescent Athletes: Risk Factors, Treatment, and Prevention

ABSTRACT

Injury to the flexor pronator mass is a common condition that is especially prevalent in overhead throwing athletes. The increasing incidence of these injuries has promoted considerable efforts in research to better understand the pathology, risk factors, and potential mechanisms to prevent injury in these athletes. While there are numerous intrinsic and extrinsic factors associated with injury, a common theme involves chronic overuse and microtrauma with inadequate resting intervals between performances. The purpose of this review is to discuss medial elbow injuries in young athletes with a particular focus on the flexor pronator mass.

Increasing rates of ulnar collateral ligament repair outpace reconstruction in isolated injuries: review of a Texas surgical database

Background

The gold standard of treatment for ulnar collateral ligament (UCL) injuries has been reconstruction. Despite early repair studies yielding less than satisfactory results, there has been recent renewed interest in UCL repair due to improved outcomes and new technologies. Data regarding clinical use of these procedures are lacking. The purpose of this study was to define the epidemiological trends of UCL repair and reconstruction surgery from 2010 to 2019, compare demographic characteristics of patients undergoing either procedure, and determine incidence of concomitant procedures in each surgical group as well as comparing respective patient-level charges.

Methods

A retrospective database analysis of UCL surgeries was performed through the Texas Healthcare Information Collection database, a comprehensive and publicly available statewide billing dataset. Inclusion criteria were defined using Current Procedural Terminology billing codes for elbow UCL repair and reconstruction between 2010 through 2019, excluding patients who had concomitant elbow fractures or lateral collateral ligament tears indicative of high-energy trauma. Procedural volume changes, patient demographics, and commonly performed concomitant procedures including elbow arthroscopy, ulnar nerve surgery, and platelet-rich plasma injection were compared. Total patient-level charges were compared across groups.

Results

A total of 1664 patients were included, consisting of 484 UCL repairs and 1180 reconstructions. Total UCL surgeries increased eleven-fold when corrected for population growth from 2010 (N = 25) to 2019 (N = 315). In 2010, repair constituted 23% of all UCL tear surgeries and increased to 40% by the end of 2019. The annual frequency of UCL repair increased at a 5.4% faster rate than UCL reconstruction from 2010 to 2019 (P < .001). There were no significant differences between any demographic data between UCL repair and reconstruction except for rural surgical settings which demonstrated 1.8 times greater odds of undergoing reconstruction (P = .05). There were no differences among commonly associated procedures including ulnar nerve surgery (P = .217), elbow arthroscopy (P = .092), and platelet-rich plasma injection (P = .837) with no differences in patient-level charges at any time point (P = .47).

Conclusion

While reconstruction remains more common, the annual frequency of UCL repair is increasing at a faster rate. Since were no demographic differences aside from surgical setting, it can be inferred that patients who were previously receiving reconstruction are instead undergoing repair. This highlights the need for future studies to further identify surgical indications for the two interventions.

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.

Determinants of Biomechanical Efficiency in Collegiate and Professional Baseball Pitchers

BACKGROUND

Biomechanical efficiency, defined as fastball velocity per unit of normalized elbow varus torque, is a relatively new metric applied to improving the performance and health of baseball pitching.

PURPOSE/HYPOTHESIS

The purpose of this work was to evaluate kinematic parameters influencing biomechanical efficiency among professional and collegiate pitchers. Kinematic differences were compared between pitchers of high and low biomechanical efficiency. We hypothesized that professional pitchers would have greater biomechanical efficiency than collegiate pitchers.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A deidentified biomechanical database of 545 pitchers (447 professional, 98 collegiate) was analyzed. A multivariate linear regression model was used to evaluate significant findings a priori with α = .05. Additionally, biomechanical differences were identified between competition levels and between high and low biomechanical efficiency groups using Mann-Whitney U test (α = .05).

RESULTS

Competition level and 11 (of 21) kinematic variables explained 27% of the variance in biomechanical efficiency, with most of the predictors being throwing arm kinematics (elbow flexion at stride foot contact [SFC]: β, -1.47; SE, 0.26; shoulder abduction at SFC: β, -1.78; SE, 0.39; shoulder external rotation at SFC: β, 0.60; SE, 0.22; maximum external rotation [MER] angle: β, 1.82; SE, 0.42; shoulder horizontal adduction at MER: β, -3.42; SE, 0.71) (all P≤ .05). Professional pitchers had greater biomechanical efficiency than collegiate pitchers (711.0 ± 101.0 vs 657.0 ± 99.3, respectively; P < .001; d = 0.53). Compared with the low-efficiency group, the high-efficiency group had significantly lower normalized elbow varus torque with greater weight and height (high: 0.047 ± 0.004 %wt*ht vs. low: 0.063 ± 0.006 %wt*ht, P <.001; d = 3.20). At the instant of SFC, the high-efficiency group demonstrated greater shoulder external rotation and less elbow flexion, shoulder abduction, and pelvic rotation. The high-efficiency group also had greater MER and less shoulder horizontal adduction at MER, trunk side tilt at ball release, and knee excursion from foot contact to ball release.

CONCLUSION

Professional pitchers had greater biomechanical efficiency than collegiate pitchers. Biomechanical efficiency was also affected by 11 kinematic variables identified in this study. Pitchers with higher efficiency had distinct differences in arm position, trunk side tilt, and lead-knee extension range of motion in the delivery. Thus, pitchers and baseball organizations should focus on these factors to lower normalized elbow varus torque relative to ball velocity.

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.

Shoulder and Elbow Injuries in Elite Taiwanese High School Baseball Pitchers From 2016 to 2017

Background

Numerous studies have discussed the risk factors for shoulder and elbow injuries in high school baseball players worldwide.

Purpose

To determine the risk factors for pitching-related shoulder and elbow injuries in Taiwanese high school pitchers.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

Included in the study were 144 pitchers from 11 top-ranked Taiwanese high school baseball teams between 2016 and 2017 high school baseball season. The participants answered a 55-item questionnaire concerning physical characteristics, pitching activities, injury history, and off-season activities. Univariate analyses were conducted separately for participants with and those without a pitching-related injury in the 12-month study period. The chi-square test or Fisher exact test was applied to categorical variables, and the F test or t test was applied to continuous variables. A stepwise multivariate logistic regression analysis was used to identify factors related to pitching-related injuries, and those results were calculated as odds ratios (ORs).

Results

Having a pitching-related injury was significantly related to the number of pitches per week in the past 12 months (OR, 1.01; P = .006), pain over the shoulder and/or elbow in the past 12 months (OR, 3.56; P = .008), pitching competitive baseball for more than 8 of the past 12 months (OR, 2.53; P = .036), throwing sliders (OR, 2.97; P = .026), and lack of participating in other over-the-shoulder activities (0.03-0.11 fewer odds; P ≤ .010).

Conclusion

For elite high school pitchers in Taiwan, pitching-related shoulder and elbow injuries were related to the number of pitches per week, pitching competitive baseball for more than 8 of the past 12 months, pain over the shoulder and/or elbow in the past 12 months, throwing sliders, and a lack of participation in other sports with over-the-shoulder activities.

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.

Four-dimensional computed tomography evaluation of shoulder joint motion in collegiate baseball pitchers

The purpose of this study is to evaluate the glenohumeral contact area, center of glenohumeral contact area, and center of humeral head during simulated pitching motion in collegiate baseball pitchers using four-dimensional computed tomography (4D CT). We obtained 4D CT data from the dominant and non-dominant shoulders of eight collegiate baseball pitchers during the cocking motion. CT image data of each joint were reconstructed using a 3D reconstruction software package. The glenohumeral contact area, center of glenohumeral contact area, center of humeral head, and oblateness of humeral head were calculated from 3D bone models using customized software. The center of glenohumeral contact area translated from anterior to posterior during maximum external rotation to maximum internal rotation (0.58 ± 0.63 mm on the dominant side and 0.99 ± 0.82 mm on the non-dominant side). The center of humeral head translated from posterior to anterior during maximum external rotation to maximum internal rotation (0.76 ± 0.75 mm on the dominant side and 1.21 ± 0.78 mm on the non-dominant side). The increase in anterior translation of the center of glenohumeral contact area was associated with the increase in posterior translation of the center of humeral head. Also, the increase in translation of the center of humeral head and glenohumeral contact area were associated with the increase in oblateness of the humeral head. 4D CT analyses demonstrated that the center of humeral head translated in the opposite direction to that of the center of glenohumeral contact area during external rotation to internal rotation in abduction in the dominant and non-dominant shoulders. The oblateness of the humeral head may cause this diametric translation. 4D CT scanning and the software for bone surface modeling of the glenohumeral joint enabled quantitative assessment of glenohumeral micromotion and be used for kinematic evaluation of throwing athletes.

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.

Lead Foot Progression Angle in Baseball Pitchers: Implications to Ball Velocity and Upper-Extremity Joint Moments

The instant of foot contact is an important transition point during the pitch cycle between the linear portion of the pitch, as a pitcher strides down the mound and the rotational portion of the pitch. Understanding the implications of lead foot angle at foot contact is an essential information needed to assist pitching coaches in their work with individual pitchers. Therefore, the purpose of this study was to determine the association between lead foot progression angle at foot contact and ball velocity, elbow varus moment, and pelvic rotation. Kinematic and kinetic data were collected from 99 collegiate pitchers and analyzed using a random intercept, mixed-effects regression model. Significant associations were found between lead foot progression angle at foot contact and elbow varus moment (P = .004), as well as pelvic rotation throughout the pitching motion (P < .001). The data indicate that increased lead foot internal rotation at foot contact is associated with increases in the elbow varus moment but is not associated with ball velocity. This study provides scientific evidence that the rotational positioning of the lead foot can affect both pelvic motion and upper-extremity joint moments.

Torso kinematic patterns associated with throwing shoulder joint loading and ball velocity in Little League pitchers

The purpose of this study was to investigate the associations between kinematic patterns of the torso segment and shoulder joint loading as well as pitching performance in youth pitchers. Twenty-four Little League pitchers threw fastballs while motion capture and force plate data were collected and ball speed was measured with a radar gun. Three-dimensional torso segment kinematics (absolute angles and angular velocities) and shoulder net joint moments (NJM) and forces were calculated. The time-series kinematic data were used as inputs to a principal components analysis to extract torso movement patterns. Associations between torso movement patterns and discrete peak shoulder NJM, compressive force, and ball speed were investigated with nonparametric correlations. Torso segment motion patterns related to forward flexion, lateral flexion (away from pitching arm), and axial rotation and rotational velocities were associated with shoulder joint kinetics and ball speed. In addition, excessive axial (transverse plane) torso rotation at ball release correlated positively with shoulder joint loads but not ball speed, which may indicate the prospect for decreasing joint kinetics while maintaining pitching performance through targeted interventions. These results provide a deeper understanding about the interrelationships between torso kinematic patterns, shoulder kinetics, and pitching performance.

Reliability of an Observational Biomechanical Analysis Tool in Adolescent Baseball Pitchers

BACKGROUND

Improper pitching mechanics are a risk factor for arm injuries. While 3-dimensional (3D) motion analysis remains the gold standard for evaluation, most pitchers and clinicians do not have access to this costly technology. Recent advances in 2-dimensional (2D) video technology provide acceptable resolution for clinical analysis. However, no systematic assessment tools for pitching analysis exist.

PURPOSE

To determine the reliability of the Assessment of biomeChanical Efficiency System (ACES) screening tool using 2D video analysis to identify common biomechanical errors in adolescent pitchers.

STUDY DESIGN

Cross-sectional.

METHODS

Adolescent baseball pitchers underwent analysis using 2D video in indoor settings. Observational mechanics were collected using a 20-item scoring tool (ACES) based on 2D video analysis. Fleiss' kappa, interclass correlation coefficients (ICC), and frequencies were used to examine intra-/interrater reliability based on common pitching errors.

RESULTS

Twenty asymptomatic pitchers ages 12-18 years were included. Total ACES scores ranged from 1 to 13, normally distributed. ACES total score demonstrated excellent intra-rater reliability within each rater (ICC for rater 1 = 0.99 (95% CI; 0.98, 0.99); ICC for rater 2 = 0.94; 95% CI: 0.84, 0.97); ICC for rater 3 = 0.98 (95% CI: 0.96, 0.99)). There was excellent interrater reliability across the trials and raters (ICC = 0.91; 95% CI: 0.82, 0.96). The ACES tool demonstrated acceptable kappas for individual items and strong ICC 0.91 (95% CI: 0.82, 0.96) for total scores across the trials. Regarding identification of biomechanical errors, "front side position" was rated erroneous in 84/120 ratings (70%), stride length in 52/120 ratings (43.3%) and lead hip position in 53/120 ratings (44.2%).

CONCLUSIONS

The 20-item ACES scoring tool with 2D video analysis demonstrated excellent intra- and interrater reliability when utilized by raters of different musculoskeletal disciplines. Future studies validating 2D vs. 3D methodology are warranted before ACES is widely disseminated and utilized for adolescent pitchers. ACES is a practical and reliable clinical assessment tool utilizing 2D video analysis for coaches, instructors, and sports medicine providers to screen adolescent pitchers for common biomechanical errors.

LEVEL OF EVIDENCE

3b.

Risk Factors for Throwing-Related Shoulder and Elbow Pain in Adolescent Baseball Players: A Prospective Study of Physical and Developmental Factors

Background:

Throwing-related shoulder and elbow pain continues to be reported among adolescent baseball players. Few prospective studies have specifically examined the association between throwing-related shoulder and elbow pain and physical and developmental changes.

Purpose:

To evaluate the changes in physical and developmental characteristics during 1 year with respect to throwing-related shoulder and elbow pain in adolescent baseball players.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

This 1-year prospective follow-up study investigated 164 baseball players aged 7 to 13 years. Player data (age, height, weight, field position, and pitch count), lower extremity muscle tightness, and range of motion (ROM) of the shoulder, elbow, and hip joints were assessed during the 2016 and 2017 preseason medical examinations. After the 2016 season, the participants completed questionnaires related to throwing-related shoulder and elbow pain, defined as an inability to play for ≥1 week because of elbow or shoulder difficulties. For study participants with and without throwing-related shoulder or elbow pain during the 2016 season, we conducted univariate and multivariate logistic regression analysis to identify risk factors for throwing-related shoulder or elbow pain.

Results:

Overall, 21 players (12.8%) reported a shoulder pain episode, 56 players (34.1%) had an elbow pain episode, and 70 players (42.7%) reported having experienced shoulder and/or elbow pain during the 2016 season. In multivariate logistic regression analysis, (1) shoulder pain was associated with 2016 preseason height (odds ratio [OR], 1.06; 95% CI, 1.01-1.11; P = .01) and change in dominant-side elbow extension ROM from 2016 to 2017 (OR, 1.12; 95% CI, 1.02-1.24; P = .02); (2) elbow pain was associated with change in weight from 2016 to 2017 (OR, 1.21; 95% CI, 1.04-1.41; P = .014); and (3) throwing-related shoulder and/or elbow pain was associated with greater 2016 preseason height (OR, 1.04; 95% CI, 1.003-1.68; P = .03) and an increase in height from 2016 to 2017 (OR, 1.17; 95% CI, 1.01-1.35; P = .03).

Conclusion:

Our results indicated that adolescent baseball players who were taller in the preseason and those with an increase in height over the 1-year study period faced significant risks for developing throwing-related shoulder and/or elbow pain.

Relationships between Hip Flexibility and Pitching Biomechanics in Adolescent Baseball Pitchers

CONTEXT

Inadequate hip active range of motion (AROM) may stifle the energy flow through the kinematic chain and decrease pitching performance while increasing the risk for pitcher injury.

OBJECTIVE

To examine the relationship of hip AROM and pitching biomechanics during a fastball pitch in adolescent baseball pitchers.

DESIGN

Cross-Sectional study.

SETTING

Biomechanics laboratory.

PARTICIPANTS

A voluntary sample of 21 adolescent baseball pitchers (16.1 ± 0.8 yrs.; 183.9 ± 5.2 cm; 77.9 ± 8.3 kg). Main Outcome Measure (s): Bilateral hip internal rotation (IR), external rotation (ER), flexion, extension, and abduction AROM were measured. Three-dimensional biomechanics were assessed as participants threw from an indoor pitching mound to a strike zone net at regulation distance. Pearson correlation coefficients were used to determine correlations between hip AROM and biomechanical metrics.

RESULTS

Statistically significant negative correlations were found at foot contact between back hip ER AROM and back hip abduction angle (p=0.030, r=-0.474), back hip ER AROM and torso rotation angle (p=0.032, r=-0.468),and back hip abduction AROM and lead hip abduction angle (p=0.037, r=-0.458). Back hip extension AROM was positively correlated with increased stride length (p=0.043, r=0.446). Lead hip abduction AROM was also positively correlated with normalized elbow varus torque (p=0.034, r=0.464).

CONCLUSIONS

There were several relationships between hip AROM and biomechanical variables during the pitching motion. The findings support the influence hip AROM can have on pitching biomechanics. Overall, greater movement at the hips allows for the kinematic chain to work at its maximal efficiency, increasing pitch velocity potential.

Effect of Forearm Position on Glenohumeral External Rotation Measurements in Baseball Players

BACKGROUND

Alterations in glenohumeral internal rotation (GIR), glenohumeral external rotation (GER), and the total arc of motion (TAM) have been linked with increased injury risk in the shoulder and elbow. These motions have been routinely measured with the forearm in neutral rotation (GIRN, GERN, TAMN). GER capacity appears to be especially important. The throwing motion, however, requires forearm pronation as GER occurs to achieve optimal cocking (GERP). No previous studies have evaluated GERP to determine GER capacity or pronated TAM (TAMP) values.

HYPOTHESIS

There would be significant differences between GERN and TAMN and between GERP and TAMP.

STUDY DESIGN

Cross-sectional.

LEVEL OF EVIDENCE

Level 3.

METHODS

Sixty asymptomatic male Minor League Baseball players (32 pitchers, 28 position players) participated in the study and were tested on the first day of spring training. Passive range of motion measurements were recorded using a long-arm bubble goniometer for GIRN, GERN, and GERP on both arms. TAM was calculated separately as the sum of internal and external rotational measurements under neutral and pronated conditions.

RESULTS

Within pitchers and position players, all measurements were statistically reduced for the throwing arm (P ≤ 0.03) except for GERN of the pitchers. GERP measures were significantly less than GERN for both arms of each group (P < 0.01): pitchers throwing arm +11.8°/nonthrowing arm +4.8°, position players throwing arm = +8.6°/nonthrowing arm +4.0°.

CONCLUSION

The forearm position of pronation, which appears to be mediated by tightness of the biceps, decreases GER capacity and TAM. GER and TAM should be calculated in neutral and pronated positions, considering that 80% of the players have a demonstrated difference between 8° and 12°.

CLINICAL RELEVANCE

Measurement of GERP more accurately reflects the GER required in throwing, allows better quantification of the motion capacity necessary to withstand the loads in throwing, and may suggest interventions for at risk athletes.

Relationship between upper limb injuries and hip range of motion and strength in high school baseball pitchers

We aimed to examine the relationship between hip range of motion (ROM) and abduction strength and throwing-related shoulder/elbow injuries in high school baseball pitchers. The study included 135 baseball pitchers. We asked them to fill out a questionnaire at the checkups, that included the dominant arm and the years of baseball experience. To avoid a confirmation bias, the examiners were blinded to the participants' hand dominance. All players underwent physical function measurements, such as height, weight, shoulder and hip strength, and shoulder and hip ROM. Shoulder and elbow injury was defined as shoulder and elbow pain that the patient had been aware of in the past 3 years. The results of injured and non-injured pitchers were compared. Eighty-five pitchers had experienced a shoulder or elbow injury in the past 3 years. The shoulder ROM and strength in the injured and non-injured groups did not differ to a statistically significant extent. The hip external rotation ROM on the dominant side, the hip abduction strength on the non-dominant side, and the hip abduction strength on the dominant side were significantly lower in the injured group than in the non-injured group. The results may contribute to reducing the incidence of these injuries.

Risk factors for throwing elbow injuries during pitching analyzed by simulation using human musculoskeletal model in youth baseball pitchers

BACKGROUND

Pitching mechanics are believed to be risk factors for throwing elbow injury. Thus, a prospective study of abnormal mechanics in youth baseball players is needed. This study aimed to analyze the ulnar collateral ligament during normal pitching using SIMM (Software for Interactive Musculoskeletal Modeling) for analysis and investigate the risk parameters of throwing elbow injuries in youth baseball players. We hypothesized that excessive ulnar collateral ligament force during pitching would be a risk factor for throwing elbow injuries in this population.

METHODS

In this cohort study, youth baseball pitchers (aged 9-11 years) were instructed to throw a ball into a netted target. Using a SIMM musculoskeletal model, we analyzed the force of the anterior band of the anterior oblique ligament, posterior band of the anterior oblique ligament (AOL_PB), and elbow varus moment during pitching (foot contact to ball release). We calculated the integral of each force of the anterior band of the anterior oblique ligament and AOL_PB during pitching and summarized these data to establish an impulse at the medial epicondyle. Each participant was followed up for 12 months to assess the occurrence of throwing elbow injury.

RESULTS

During the 12-month follow-up period, 18 pitchers (28.1%) reported throwing elbow injuries in the throwing arm. The results of this study showed that the maximum AOL_PB force and the impulse at the medial epicondyle were risk factors for throwing elbow injuries. The maximum AOL_PB force was significantly higher in the throwing elbow injury group than in the uninjured group (59.4 ± 17.8 N vs. 47.1 ± 17.5 N, P = .014). The impulse at the medial epicondyle was also significantly different (11.1 ± 4.0 N ･ s in the throwing elbow injury group vs. 8.3 ± 4.4 N ･ s in the uninjured group, P = .025).

CONCLUSIONS

Increasing the AOL_PB force or the impulse at the medial epicondyle may increase the risk of throwing elbow injuries in youth baseball pitchers. It may be possible to reduce injury risk by focusing on ways to decrease AOL_PB load and cumulative stress on the medial epicondyle throughout the throwing motion while still maintaining high levels of ball velocity.

Youth Baseball Caregiver Understanding of Safe Pitching Guidelines and Player Injury

BACKGROUND

As more athletes participate in youth baseball, there has been an associated increase in upper extremity injuries. Knowledge of baseball injury prevention guidelines continues to be developed and defined as throwing-related injuries rise. The purpose of this study was to evaluate how knowledgeable youth baseball caregivers were about safe pitching guidelines and secondarily determine pitching practices which may be associated with increased risk of player injury.

METHODS

A twenty-two question survey comprised of demographic data, knowledge of overhead throwing guidelines, pitching history, presence of risk factors associated with overhead throwing and pitching habits was distributed to the caregivers of youth baseball pitchers in North Central Florida.

RESULTS

Eighty-three percent (81/98) of those polled were unaware of the existence of safe pitching guidelines, regardless of the pitcher's playing experience (p > 0.05). Those who pitched more than six months out of the year were significantly more prone to experience throwing arm pain after a performance (p < 0.05). Fifty-two percent (51/98) of the caregivers recalled their child having throwing arm pain as a direct result of pitching, with twenty-six percent (25/98) of pitchers having to miss either a game or a pitching appearance. Twenty-seven percent (26/98) of all players went on to seek medical evaluation for arm discomfort due to pitching. Pitchers 13 years of age and older were more likely to throw curveballs and miss games because of throwing arm pain (p < 0.05).

CONCLUSION

Despite implementation and accessibility of safe pitching guidelines, a large portion of those surveyed were unaware or noncompliant with these established recommendations. Given the results of this study, further measures need to be taken to improve caregivers' understanding of current guidelines to help increase compliance and protect youth pitchers.

LEVEL OF EVIDENCE

Cross-sectional survey study, 3b.

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

BACKGROUND

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

PURPOSE/HYPOTHESIS

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

STUDY DESIGN

Retrospective cross-sectional study.

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

3.

Hip Abduction Strength: Relationship to Trunk and Lower Extremity Motion During A Single-Leg Step-Down Task in Professional Baseball Players

BACKGROUND

The single-leg step down task (SLSD) is a clinical tool to assess movement and control of the lower extremity and trunk. Hip abduction weakness may impact movement quality during the SLSD, however the relationships between movement and strength are unclear.

PURPOSE

To determine the relationship between hip abduction isometric strength and movement during the SLSD of trunk lean, pelvic drop, knee valgus, and hip flexion.

STUDY DESIGN

Cross sectional, cohort study.

METHODS

One hundred-eighteen Minor League baseball players (age=21.6 ± 2.0 years; n=68 pitchers, n=50 position players) participated. Bilateral hip abduction isometric strength was measured using a handheld dynamometer (HHD), and then multiplied by distance from the greater trochanter to the HHD and expressed as hip abduction torque. Video cameras captured the SLSD, with participants standing on one leg while lowering their contralateral heel to touchdown on the floor from a 0.203m (8in.) step. Trunk lean, trunk flexion, pelvic drop, knee valgus, and hip flexion were measured using Dartfish at heel touchdown. A value of 180° indicated no knee valgus. Pearson correlations examined the relationships between hip abduction torque and SLSD motions.

RESULTS

There were no significant correlations for position players. For pitchers, on the lead leg increased hip abduction torque weakly correlated with a decrease in knee valgus (r= 0.24, p=0.049). Also for pitchers on the trail leg, increased hip abduction torque weakly correlated with decreased pelvic drop (r= -0.28, p=0.021).

CONCLUSION

Hip abduction strength contributes to dynamic control of the trunk and legs. Specifically in pitchers, hip abduction weakness was related to increased movement of the lower extremity and lumbopelvic regions during the dynamic SLSD task. These deficits could translate to altered pitching performance and injury.

LEVELS OF EVIDENCE

2.

Shadow pitching deviates ball release position: kinematic analysis in high school baseball pitchers

Background

Although shadow pitching, commonly called “towel drill,” is recommended to improve the throwing motion for the rehabilitation of pitching disorders before the initiation of a throwing program aimed at returning to throwing using a ball, the motion differs from that of normal throwing. Learning improper motion during ball release (BR) may increase shoulder joint forces. Abnormal throwing biomechanics leads to injures. However, there has been no study of shadow pitching focusing on the BR position. The purpose of the present study was to evaluate the BR position and kinematic differences between shadow pitching and normal throwing. In addition, the effect of setting a target guide for BR position on throwing motion was examined in shadow pitching.

Methods

The participants included in this study were 20 healthy male students who were overhand right-handed pitchers with no pain induced by a throwing motion. Participants performed normal throwing (task 1), shadow pitching using a hand towel (task 2), and shadow pitching by setting a target of the BR position (task 3). A motion capture system was used to evaluate kinematic differences in throwing motions, respectively. Examination items comprised joint angles and the differences in BR position.

Results

BR position of task 2 shifted significantly toward the anterior, leftward, and downward directions compared with task 1. The distance of BR position between tasks 1 and 2 was 24 ± 10%. However, task 3 had decreased BR deviation compared with task 2 (the distance between 3 and 1 was 14 ± 7%). Kinematic differences were observed among groups at BR. For shoulder joint, task 2 showed the highest value in abduction and horizontal adduction among groups. In spine flexion, left rotation and thorax flexion, task 2 was significantly higher than task 1. Task 3 showed small differences compared with task 1.

Conclusions

The BR position of shadow pitching deviated significantly in the anterior, leftward, and downward directions compared with normal throwing. Furthermore, we demonstrated that the setting of BR target reduces this deviation. Thus, the target of BR position should be set accurately during shadow pitching exercises in the process of rehabilitation.

Relationship between the Lower Limb Function and Shoulder and Elbow Injuries in Elementary School Baseball Pitchers

Objectives

We aimed to examine the relationship between the hip range of motion (ROM) and ankle ROM and throwing-related shoulder and elbow injuries in elementary school baseball pitchers.

Methods

This retrospective comparative study (Level of evidence: Level III) included 195 baseball pitchers (mean age 10.8±1.0 years, range 8-12 years). All pitchers underwent physical function measurements, including height, weight, shoulder strength, and hip and ankle ROM. Shoulder and elbow injury was defined as shoulder and elbow pain that the pitchers had been aware of in the past or at the time of medical checkups. The results for the injured and non-injured groups were then compared.

Results

The shoulder ROM and strength in the injured and non-injured groups did not differ to a statistically significant extent. The hip external rotation on the dominant side (injured vs. non-injured: 48.9±11.1° vs. 53.3±9.7°, P<0.01), the hip internal rotation on the non-dominant side (injured vs. non-injured: 36.6±12.0° vs. 40.9±11.0°, P=0.01), and ankle plantar flexion on the non-dominant side (injured vs. non-injured: 52.0±6.8° vs. 54.3±6.7°, P=0.02) were significantly smaller in the injured group than in the non-injured group.

Conclusions

The hip external rotation ROM on the dominant side and the hip internal rotation and ankle plantar flexion on the non-dominant side were significantly lower in the injured group than in the non-injured group. These results may suggest measures to reduce the incidence of elbow and shoulder injuries in elementary school baseball pitchers.

Relationship Between Upper Limb Injuries and Hip Range of Motion in Elementary and Junior High School Baseball Players

Background:

Shoulder and elbow injuries are major problems in baseball players. Tightness of the upper extremities has been reported as a risk factor for shoulder and elbow injuries in elementary and junior high school baseball players. However, few studies have been conducted on the relationship between decreased hip range of motion (ROM) and shoulder and elbow injuries.

Purpose/Hypothesis:

This study aimed to prospectively examine the relationship between hip ROM and throwing-related shoulder and elbow injuries in elementary and junior high school baseball players. The hypothesis was that players with unrestricted ROM in the hip would have a reduced risk of upper extremity injuries.

Methods:

The study included 263 baseball players (mean ± SD age, 10.5 ± 1.3 years; range, 7-14 years). The following physical parameters were assessed: (1) hip flexion ROM measured in the supine position and (2) hip internal and external rotation in the prone position. After the season, players completed questionnaires regarding shoulder and/or elbow injuries. For comparison, the players were classified as injured (not able to play for ≥8 days because of shoulder and/or elbow problems) or noninjured.

Results:

During the season, 52 players had shoulder and/or elbow injuries. When the injured and noninjured groups were compared, hip flexion on the dominant side (121.5° ± 12.0° vs 126.7° ± 9.8°, respectively; P < .01), hip flexion on the nondominant side (119.6° ± 11.7° vs 126.0° ± 9.9°, respectively; P < .01), and internal rotation on the dominant side (52.5° ± 11.3° vs 56.8° ± 10.8°, respectively; P = .01) were significantly reduced in the injured group.

Conclusion:

We identified preseason decreases in flexion bilaterally and internal rotation on the dominant side as risk factors for shoulder and elbow injuries in elementary and junior high school baseball players. Further studies are required to prevent disabilities in elementary and junior high school baseball players through development of prevention and intervention programs.

A New Method for Evaluating Pelvic and Trunk Rotational Pitching Mechanics: From Qualitative to Quantitative Approaches

The purpose of this study was to build on existing qualitative to quantitative approaches to develop a new quantitative method for evaluating pelvic and trunk rotational pitching mechanics. Thirty pitchers were divided into two groups ("Pattern1": closed "hip-to-shoulder separation"; "Pattern2": open "hip-to-shoulder separation"). Several parameters were analyzed. Higher ball speeds were found in group of Pattern1, four key characteristics of which were identified. Based on the results, a new evaluation method was developed. Pelvic and trunk rotational mechanics were classified into four types. Type1 (proper mechanics) enabled significantly higher ball speed than the other three types and was thought to involve proper energy transfer from the stride foot to the throwing upper limb. Types 2-4, however, were regarded as "improper mechanics", which could result in slower ball speeds and less efficient energy transfer. A qualitative approach, based on "expert opinion", can specify optimal pelvis and trunk rotational mechanics. However, quantitative analysis is more precise in identifying three improper types of pelvis and trunk rotational mechanics. Furthermore, special programs, such as core strengthening and flexibility training, can be developed for various improper practices in order to improve pitching mechanics.

Stride-Phase Kinematic Parameters That Predict Peak Elbow Varus Torque

Background:

During baseball pitching, a high amount of elbow varus torque in the arm cocking-to-acceleration phase is thought to be a biomechanical risk factor for medial elbow pain and injury. The biomechanics of the stride phase may provide preparation for the arm cocking-to-acceleration phase that follows it.

Purpose:

To determine the kinematic parameters that predict peak elbow varus torque during the stride phase of pitching.

Study Design:

Descriptive laboratory study.

Methods:

Participants were 107 high school baseball pitchers (age range, 15-18 years) without shoulder or elbow problems. Whole-body kinematics and kinetics during fastball pitching were analyzed using 3-dimensional measurements from 36 retroreflective markers. A total of 26 kinematic parameters of the upper and lower limbs during the stride phase leading up to the stride foot contact were extracted for multiple regression analysis to assess their combined effect on the magnitude of peak elbow varus torque.

Results:

Increased wrist extension, elbow pronation, knee flexion on the leading leg, knee extension on the trailing leg at stride foot contact, and upward displacement of the body’s center of mass in the stride phase were significantly correlated with decreased peak elbow varus torque (all P < .05). Moreover, 38% of the variance in peak elbow varus torque was explained by a combination of these 5 significant kinematic variables (P < .001).

Conclusion:

We found that 5 kinematic parameters during the stride phase and the combination of these parameters were associated with peak elbow varus torque. The stride phase provides biomechanical preparation for pitching and plays a key role in peak elbow varus torque in subsequent pitching phases.

Clinical Relevance:

The present data can be used to screen pitching mechanics with motion capture assessment to reduce peak elbow varus torque. Decreased peak elbow varus torque is expected to reduce the risk of elbow medial pain and injury.

The Influence of Pitch Velocity on Medial Elbow Pain and Medial Epicondyle Abnormality Among Youth Baseball Players

BACKGROUND

Pitch velocity is associated with elbow injuries among skillful baseball players. However, the relationship between pitch velocity and throwing elbow injuries among youth players has not yet been clarified.

PURPOSE

To investigate the influence of pitch velocity on medial elbow pain and medial epicondyle abnormality among youth baseball players.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

The participants consisted of 256 elementary school players (mean age, 11 ± 1 years; range, 9-12 years). The medial aspect of the elbow was evaluated using ultrasound imaging. A questionnaire was used to investigate past or present pain in the elbow, background of the players (age, height, body mass index, and years of baseball experience), and playing environment (number of days of practice in a week, experience as a pitcher, and cryotherapy of the shoulder and elbow after practice). Positioning of the scapula, range of motion in shoulder internal/external rotations and hip internal rotation, angle of the straight-leg raise, and heel-to-buttock distance were measured. The pitch velocity was recorded using a pitch velocity radar gun. The relationship between these variables and the presence of medial epicondyle abnormality, as well as past or present elbow pain, were statistically analyzed.

RESULTS

A medial epicondyle abnormality was observed in 130 players (51%), elbow pain in the past in 65 players (25%), and elbow pain during the examination in 14 players (5%). Sixty-nine players (27%) experienced elbow pain either in the past or during examination. Abnormality of the medial epicondyle had a relationship with the pitch velocity (odds ratio [OR], 1.1 for increase of 1 km/h; 95% CI, 1.1-1.2; P < .0001) and the number of practice days in a week (OR, 1.8 for increase of the practice days; 95% CI, 1.4-2.5; P < .0001). Pitch velocity was also significantly related with past pain, present pain, and past and/or present pain of the elbow (OR [km/h], 1.1, 1.1, 1.1; 95% CI, 1.0-1.1, 1.0-1.2, 1.1-1.2; P < .0001, P = .002, P < .0001, respectively).

CONCLUSION

Pitch velocity was significantly associated with abnormality of the medial epicondyle and elbow pain. A 10-km/h increase in pitch velocity would increase the risk of medial epicondyle abnormality and medial elbow pain by 3 times.

Predictors of elbow torque among professional baseball pitchers

BACKGROUND

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Sport Specialization and Increased Injury Frequency in Youth Baseball Players: A Prospective Study

CONTEXT

Sport specialization is thought to be a primary contributor to the throwing-related injury risk in youth baseball players.

OBJECTIVE

To (1) establish arm-injury incidence in a cohort of male youth (9-12 years old) baseball players and (2) examine sport specialization and the frequency of arm injuries in the same cohort.

DESIGN

Cohort study.

SETTING

Greenville, South Carolina, youth baseball programs and tournaments.

PATIENTS OR OTHER PARTICIPANTS

A total of 159 asymptomatic youth baseball players (age = 11.1 ± 1.1 years) were physically assessed and then were prospectively followed for 6.7 ± 1.5 months.

MAIN OUTCOME MEASURE(S)

Athlete demographics and playing and injury histories were initially recorded. Athlete-exposures and presence of arm injury were prospectively tracked. All injuries were physically confirmed by a licensed physical therapist.

RESULTS

Youth players demonstrated an arm-injury incidence rate of 2.22 per 1000 athlete-exposures. Parents and players underestimated sport-specialization status based on the standard research definition (self versus research based: 31% versus 83%, respectively; P = .001). The frequency of arm injuries was higher in specialized players (100%) than in nonspecialized players (80%, P = .03) but did not differ between pitchers and position players (13.2% each, P = 1.00).

CONCLUSIONS

Sport specialization was associated with throwing-related arm injuries in a small cohort of youth baseball players. It is concerning that 57.9% of parents and specialized players were unaware of the athletes' status. Larger studies with longer follow-up periods are needed to further evaluate injury-risk profiles in physically developing youth populations.