Deficits in Glenohumeral Passive Range of Motion Increase Risk of Shoulder Injury in Professional Baseball Pitchers: A Prospective Study

Shoulder External Over Internal Rotation Ratio Is Related to Biomechanics in Collegiate Baseball Pitching

Altering baseball pitching mechanics affects both performance and the risk of injury. The purpose of this study is to investigate the relationships of shoulder external over internal rotation ratio (SEIR) and other shoulder rotational properties during physical exam and biomechanics of pitching for 177 collegiate baseball pitchers. The shoulder range of motion was quantitatively measured using a custom-made wireless device. Pitching motion data were collected at 240 Hz, and a custom program was created to calculate the throwing arm motion and loading during baseball pitching. Linear regression and analysis of variance tests were performed to investigate the relationships between the shoulder physical exam outcomes and throwing arm biomechanics. SEIR had significant correlations with shoulder horizontal adduction angle at foot contact, maximum shoulder external rotation angle, maximum shoulder linear velocity, and elbow angle at ball release. SEIR groups had significant differences in shoulder proximal force, adduction torque, internal rotation torque, and horizontal adduction torque, and in elbow medial force and varus torque. Glenohumeral internal rotation deficit and total rotational motion deficit had no relationships with throwing arm motions or joint loadings. Shoulder health should be monitored to improve understanding of pitching mechanics in collegiate baseball pitchers.

Throwing Shoulder Adaptations Are Not Related to Shoulder Injury or Pain: A Preliminary Report

BACKGROUND

Overhead throwing in baseball and softball athletes induces shoulder adaptations theorized to increase risk of shoulder musculoskeletal injury (MSI) and/or pain due to range of motion (ROM) deficits.

HYPOTHESIS

Shoulder ROM adaptations are associated with a higher risk for developing shoulder MSI and pain.

STUDY DESIGN

Prospective cohort study.

LEVEL OF EVIDENCE

Level 3.

METHODS

A total of 60 National Collegiate Athletic Association Division I athletes cleared for full athletic participation and free from upper extremity MSI in the last 4 weeks (age, 19.0 ± 1.2 years; weight, 82.1 ± 13.7 kg; height, 178.6 ± 11.2 cm; softball, n = 23; baseball, n = 37). Passive glenohumeral internal rotation (IR), external rotation (ER), and horizontal adduction (HA) ROM were measured with the scapula stabilized and used to categorize participants with/without external rotation gain (ERG), external rotation insufficiency (ERI), glenohumeral internal rotation deficit (GIRD), pathological GIRD, and posterior shoulder tightness (PST) before the competitive season. Groups were then compared to assess the incidence of shoulder MSI prospectively and prevalence of shoulder pain at the initial evaluation.

RESULTS

Baseball and softball athletes demonstrated significantly less IR ROM in the dominant shoulder (50.6° ± 9.4°) compared with the nondominant shoulder (59.1° ± 8.6°; P < 0.01) and significantly more ER ROM (dominant, 104.6° ± 12.1°; nondominant, 97.7° ± 12.0°; P < 0.01). Incidence of shoulder MSI was 15% but was not significantly related to any shoulder adaptations. No significant relationship was found between prevalence of pain and any shoulder adaptations in the 27% of athletes with pain.

CONCLUSION

Increased ER and decreased IR ROM adaptations in intercollegiate overhead throwing athletes do not appear to be correlated to risk of shoulder MSI or pain.

CLINICAL RELEVANCE

The findings of this level 3 prospective study provide clinicians working with overhead athletes information regarding shoulder MSI risk and pain. It is recommended that clinicians should not use ROM adaptations exclusively to determine increased risk of shoulder MSI.

Comparison of glenohumeral and scapulothoracic kinematics between fastballs and curveballs during baseball pitching

Shoulder injuries are common in baseball pitchers and primarily involve the glenohumeral joint. Past analyses have examined shoulder biomechanics during different pitch types simply as the motion of the upper arm relative to the thorax. In this study, glenohumeral and scapulothoracic kinematics were compared between fastballs and curveballs at key timepoints throughout a pitch. Upper extremity kinematics of thirteen collegiate pitchers were collected during fastball and curveball pitches with motion capture. A linear model approach was utilised to estimate scapular kinematics based on measurable humerothoracic motion. Glenohumeral kinematics were computed from the scapular and humeral motion data. Comparisons of scapulothoracic and glenohumeral kinematic variables at times of maximum glenohumeral external rotation, ball release, and maximum glenohumeral internal rotation between pitch types were made using paired t-tests with Benjamini-Hochberg corrections. There were no significant differences in glenohumeral kinematics. Fastballs elicited significantly less scapulothoracic internal rotation and more posterior tilt at maximum glenohumeral external rotation. Fastballs produced significantly less scapulothoracic internal rotation and anterior tilt at maximum glenohumeral internal rotation. This study provides further evidence that risk of injury to the glenohumeral joint may be consistent between fastballs and curveballs and offers insights into subtle differences in scapular kinematics between pitch types.

Reproducibility and Validity of the Kerlan-Jobe Orthopedic Clinic Shoulder and Elbow Score (Japanese Version)

BACKGROUND

The Kerlan-Jobe Orthopedic Clinic (KJOC) questionnaire is a self-reported performance and functional assessment tool with good reliability and validity for overhead athletes with shoulder and elbow injuries. This study aimed to develop a Japanese version of the KJOC (J-KJOC) to clarify its reproducibility and validity for use by Japanese university baseball players.

METHODS

The J-KJOC was translated according to the guidelines for cross-cultural adaptation. A total of 88 university baseball players completed the J-KJOC and the Quick-Disabilities of the Arm, Shoulder, and Hand (Q-DASH) questionnaires. Thirty players completed the J-KJOC two times after a median interval of two weeks. We assessed the absolute reliability, construct validity, internal consistency, and test-retest reliability.

RESULTS

Cronbach's alpha coefficients ranged from 0.88 and the intraclass correlation coefficient for the total score was 0.91. A fixed bias was absent in the J-KJOC scores (mean difference: -2.2, 95% CI: -4.8 to 0.5). Furthermore, the J-KJOC score was correlated with the Q-DASH-disability/symptom (r = -0.60, p<0.01) and Q-DASH-sports/music (r = -0.63, p<0.01) scores but not correlated with the Q-DASH-work score (r = -0.11, p = 0.316).

CONCLUSIONS

The J-KJOC questionnaire demonstrated good reproducibility and validity for assessing upper arm performance in Japanese university baseball players. The results of this study support the use of the J-KJOC for Japanese-speaking baseball players. Further research using this instrument on other types of overhead athletes is needed to determine its wider utility in sports medicine applications.

Utilizing the Pronated Forearm Technique for Measuring Glenohumeral External Rotation in Baseball Players

BACKGROUND

Alterations in glenohumeral internal rotation (GIR), glenohumeral external rotation (GER), and total range of motion (TROM) have been linked with increased injury risk. GER capacity has been measured routinely with the forearm in neutral rotation (GERN), but a recent study reported GERN was greater than GER with the forearm in pronation (GERP) in Minor League pitchers. This work has not yet been replicated or extended to other groups.

HYPOTHESIS

GERP would be significantly less than GERN in Independent League baseball pitchers, and there would be no difference in GERP or GERN measurements between this new group and the previous group of Minor League pitchers.

STUDY DESIGN

Cross-sectional study.

LEVEL OF EVIDENCE

Level 3.

METHODS

Goniometric measurements were recorded for bilateral GIR, GERN, and GERP, and resulting TROM for 37 Independent League baseball pitchers. These data were compared with the previous study. All motions were compared individually between groups, between throwing and nonthrowing arm, and both within and between techniques (forearm neutral or pronated).

RESULTS

GERP was significantly less than GERN for both arms within each group tested (P < 0.01). Independent League pitchers had greater between arm differences for GIR (-16.9° vs -6.9°), GERN (+15.1° vs -0.6°), and GERP (+13.1° vs -5.9°) compared with Minor League pitchers. TROM for the Independent League pitchers was not statistically different for either measurement technique, while TROM for the throwing arm of the Minor League pitchers was statistically reduced with varying effect sizes (d = 0.35-0.99) compared with the nonthrowing arm (P < 0.01).

CONCLUSION

This study confirmed earlier findings that the pronated forearm resulted in decreased GER capacity, illustrating the adaptive response to throwing and the need to evaluate for this variable.

CLINICAL RELEVANCE

GERP should be evaluated in all groups of pitchers, but there may be variations within tested groups.

The COVID-19 lockdown as a model of detraining in division 1 college softball players

BACKGROUND

The COVID-19 pandemic interrupted the organized training of softball players, similar to the abrupt cessation of sports participation that can happen after an injury. Thus, the COVID-19 pandemic offers a unique model to study how sudden detraining influences softball players.

METHODS

We recruited a sample of convenience of National Collegiate Athletic Association Division 1 softball players. They participated in three data collections: pre-lockdown (Jan 2020, T1), post-lockdown (Sept 2020, T2), and before the 2021 season (Jan 2021, T3). Between T1 and T2, players received an at-home conditioning and throwing program, but compliance was not strictly monitored. Between T2-T3, players resumed formal fall training (team-organized workouts, on-field practice, and within-team scrimmage games). At each time point, we collected bilaterally: 1) shoulder internal rotation (IR) and external rotation (ER) range of motion (ROM); 2) shoulder IR and ER strength; 3) hip IR and ER ROM; and 4) hip abduction and extension strength. We used four independent (2 Sides × 3 Timepoints) MANOVA with repeated measures; we followed up significant MANOVA main effect of time with Sidak posthoc tests for pairwise comparisons between time points.

RESULTS

Fifteen players participated in this study. We found a significant MANOVA main effect of time for shoulder and hip ROM (p < 0.01). Between T1-T2, dominant shoulder ER ROM decreased 6.5°, dominant shoulder IR ROM increased 4.3°, and lead hip IR ROM increased 4.4°. Between T2-T3, dominant shoulder ER ROM increased 6.3° and trail hip ER ROM increased 5.9°. We found a significant MANOVA main effect of time for shoulder strength (p = 0.03) but not for hip strength (p = 0.18). Between T2-T3, non-dominant shoulder IR and ER increased 1.8 kg and 1.5 kg, respectively.

CONCLUSION

A sudden and prolonged cessation of organized training generated changes in shoulder and hip ROM but affected strength to a lesser extent. The loss of shoulder ER and increased lead hip IR ROM are maladaptive as they are associated with injury in overhead athletes. Resuming team-organized training and scrimmage reversed some (shoulder ER), but not all of these changes. Practitioners should monitor clinical variables regularly and be aware of potential changes due to unexpected and prolonged interruptions in training, such as when players suffer sports-related injuries.

Rehabilitation of the painful shoulder

Managing the painful shoulder in overhead athletes can be difficult because of a lack of time-loss injuries in overhead sports and focusing primarily on either pathoanatomic causes or movement impairments. Although managing the painful shoulder can be challenging, the combination of identifying pathoanatomic causes with movement impairments can provide a more focused rehabilitation approach directed at the causes of shoulder pain. Understanding the potential influence of scapular positioning as well as mobility and/or strength impairments on shoulder pain can help clinicians develop more directed rehabilitation programs. Furthermore, sports-specific methods such as long toss or the use of weighted balls for achieving physiological or performance-based gains have limited empirical evidence regarding their clinical and performance-based benefits, which may impede the rehabilitation process. Applying a comprehensive evaluation approach prior to and throughout the treatment process can assist clinicians with selecting the most appropriate treatment based on patient need. Reconsidering traditional treatments based on existing evidence may help refine the treatment process for overhead athletes with shoulder pain.

Defining humeral axial rotation with optical motion capture and inertial measurement units during functional task assessment

Humeral motion can be challenging to measure and analyze. Typically, Euler/Cardan sequences are used for humeral angle decomposition, but choice of rotation sequence has substantial effects on outcomes. A new method called True axial rotation calculation may be more precise. The objective of this study is to compare humeral axial rotation measured from two systems (optical motion capture and inertial measurement units (IMUs)) and calculated with two methods (Euler angles and True axial). Motion of torso and dominant humerus of thirty participants free from any upper limb impairments was tracked using both systems. Each participant performed a functional tasks protocol. Humeral axial rotation was calculated with Euler decomposition and the True axial method. Waveforms were compared with two-way ANOVA statistical parametric mapping. A consistent pattern emerged: axial rotation was not different between motion capture systems when using the True axial method (p > .05), but motion capture systems showed relatively large magnitude differences (~ 20-30°) when using Euler angle calculation. Between-calculation method differences were large for both motion capture systems. Findings suggest that the True axial rotation method may result in more consistent findings that will allow for precise measurements and comparison between motion capture systems. Two methods for calculating humeral axial rotation measured from optical motion capture and inertial measurement units were compared.

Stability, performance and upper and lower extremities range of motion in elite beach handball athletes: A cross sectional study

Although beach handball is a popular sport worldwide, information about the functional profile in elite athletes are lacking. This study generate a descriptive profile of stability, performance and upper and lower extremities ROM in elite beach handball athletes. Secondary proposals were to compare these outcome measures between sexes and sides, and to report the frequency of athletes "at risk" according to cutoff values for shoulder ROM and dynamic postural stability of the lower extremities. Twenty-eight (n = 16 males, 28.7 ± 5.3 years; n = 12 females, 27.5 ± 5.5 years) elite beach handball athletes were tested. Closed Kinetic Chain Upper Extremity Stability Test (CKCUEST), single hop test, modified Star Excursion Balance Test (mSEBT) and passive shoulder, hip and ankle dorsiflexion ROM were assessed. Male athletes presented greater reach distance in the anterior direction [P < .0001; Mean Difference (MD): 36%] and lower reach distance in the posteromedial direction (P < .0001; MD: -29.7%) than female athletes in the mSEBT. Bilateral differences were observed for male athletes during the mSEBT, with the dominant stance limb obtaining a smaller reach distance in the anterior direction (P < .01; MD: -38.3%) and greater reach distance in the posteromedial direction (P < .0001; MD: 30.8%). Male athletes had less upper and lower extremities ROM and reached a smaller normalized single hop distance than female athletes. Most athletes presented mSEBT asymmetries and shoulder ROM deficits which have been shown to increase injury risk. Dynamic postural stability adaptations are present in elite beach handball athletes of both sexes, with more pronounced upper and lower extremity flexibility deficits in male athletes.

A Field-expedient Arm Care Screening Tool Can Identify Musculoskeletal Risk Factors in Baseball Players

BACKGROUND

Preseason movement screening can identify modifiable risk factors, deterioration of function, and potential for injury in baseball players. Limited resources and time prevent high school baseball coaches from performing movement screens on their players.

HYPOTHESIS

The arm care screen (ACS) will be highly sensitive to detecting musculoskeletal risk factors.

STUDY DESIGN

Cross-sectional.

LEVEL OF EVIDENCE

Level 3.

METHODS

A total of 150 baseball players were independently scored on the ACS electronically by reviewing a video recording of each player's screening performance. Discriminability of the ACS was determined with a 2 × 2 contingency table dichotomizing musculoskeletal risk factors as present or absent based on a predetermined cutoff value and those who passed or failed the corresponding ACS subtest.

RESULTS

High sensitivity was observed on the reciprocal shoulder mobility (0.89; 95% CI 0.81-0.94), 90/90 total body rotation (0.86; 95% CI 0.79-0.92), and lower body diagonal reach (0.85; 95% CI 0.78-0.91) tests of the ACS suggesting sufficient ability to identify musculoskeletal impairments and risk factors.

CONCLUSION

The ACS is a simplistic screening tool that the coach can administer to discriminate between youth, high school, and college-level baseball players who possess musculoskeletal risk factors. The ACS subtests demonstrated high sensitivity for correctly identifying musculoskeletal risk factors common in baseball players and can be useful as a screening tool for baseball coaches developing arm care exercise programs.

CLINICAL RELEVANCE

A field-expedient screen could provide coaches the ability to identify musculoskeletal risk factors that need to be addressed to minimize injury risk factors in a time-efficient manner.

Organizational risk profiling and education associated with reduction in professional pitching arm injuries: a natural experiment

Background

Risk profiling and education are strategies implemented to help reduce injury risk; however, currently. there is little evidence on the effect of these interventions on injury incidence. The purpose of this study was to evaluate the influence of risk profiling and education on upper extremity injury incidence in minor league (MiLB) pitchers and to stratify by injury severity.

Methods

A prospective natural experiment study was conducted from 2013 to 2019 on MiLB pitchers. Beginning in the 2015 season, pitchers were examined and risk profiled for upper extremity injury. Shoulder external, internal, total range of motion, horizontal adduction, and humeral torsion were measured. Organizational risk profiling and education was implemented starting in 2015, based on preseason assessments. Chi-squared test was performed to investigate potential differences between shoulder range of motion risk categories between 2013-2014 (pre) and 2015-2019 (post) seasons. Interrupted time series analyses were performed to assess the association between organizational risk profiling and education on arm injury in MiLB pitchers and were repeated for 7-27 and 28+ day injury severity.

Results

297 pitchers were included (pre: 119, post: 178). Upper extremity injury incidence was 1.5 injuries per 1000 athletic exposures. Pitchers in the 2015-2019 seasons demonstrated increased preseason shoulder injury risk for internal (P = .003) and external (P = .007), while the 2013-2014 seasons demonstrated greater horizontal adduction risk (P = .04). There were no differences between seasons for total range of motion risk (P =.76). Risk profiling and education resulted in an adjusted time loss upper extremity injury reduction for the 2015-2019 seasons (0.68 (95% CI: 0.47, 0.99)), which impacted 7-27 days (0.62 (95% CI: 0.42, 0.93)) but not for 28+ days (0.71 (95% CI: 0.47, 1.06)) time loss. There was no reduction in combined trunk and lower extremity injuries for the 2015-2019 seasons (1.55 (95% CI: 0.79, 3.01)).

Conclusions

Organizational risk profiling and education appear to reduce professional pitching overall and 7-27-day upper extremity injury risk by 33%-38%. There was no difference in trunk and lower extremity injuries over the period, strengthening the reduction in upper extremity injury risk results. This suggests that while injury risk increased over time, organizational risk profiling mitigated the expected increase in upper extremity injury rates. Risk profiling and education can be used as a clinical screening and intervention tool to help decrease upper extremity injuries in professional baseball populations.

Reliability Analysis of In-person and Virtual Goniometric Measurements of the Upper Extremity

Background

Virtual healthcare has forced clinicians to modify or eliminate parts of the musculoskeletal evaluation such as motion assessment. Although acceptable to excellent levels of in-person goniometric reliability is achievable, reliability of virtual assessments is unknown.

Purpose

To determine if similar upper extremity goniometric measurements could be obtained in-person and virtually.

Study Design

Reliability study; classroom setting.

Methods

Publicly recruited sample over 18 years of age with no upper extremity injuries. Each subject was tested in a standing position with dominant arm facing the clinicians to visualize the landmarks for goniometer placement. Flexion and extension of the shoulder, elbow and wrist were measured. Prior to performing in-person goniometric measurements for each joint, an image was captured of each pre-determined joint position using a mobile device with a camera. This image represented the screenshot on a virtual platform. Four clinicians performed in-person measurements twice during the same session on each subject. The following week clinicians measured virtual images using the same techniques. Inter-rater and intra-rater reliability were determined via intraclass correlation coefficients (ICC).

Results

Inter-rater reliability for five of the six in-person (ICC≥0.81) and virtual measurements (ICC≥0.78 ) were classified as excellent. In-person wrist extension (ICC=0.60) and virtual wrist flexion (ICC=0.65) were classified as good. Intra-rater reliability for individual clinicians were between good and excellent for the in-person measurements (ICC:0.61-0.96) and virtual measurements (ICC:0.72-0.97). There were a greater number of excellent ICC values for the virtual measurements (90%) compared to in-person measurements (70%). There were statistically significant differences between in-person and virtual sessions for five of six measurements (p≤0.006). Only elbow extension did not differ between sessions (p=0.966).

Conclusion

Virtual assessment compared to goniometric measurements showed good to excellent inter- and intra-rater reliabilities (ICC > 0.60), which suggests clinicians can utilize goniometry either in person or on a virtual platform.

Level of Evidence

3b©The Author(s).

Is Workload Associated With Internal Impingement in Professional Baseball Pitchers? An Analysis of Days of Rest, Innings Pitched, and Batters Faced

Background

Internal impingement is a common cause of shoulder pain and dysfunction in baseball pitchers.

Purpose/Hypothesis

The purpose of this study was to determine if the amount of rest days between outings, the number of innings pitched in each outing, and the number of batters faced in each outing are risk factors for internal impingement in professional baseball pitchers. It was hypothesized that a higher workload would significantly increase a pitcher's risk of developing internal impingement.

Study Design

Case-control study; Level of evidence, 3.

Methods

All professional (Major and Minor League) baseball pitchers who were diagnosed with internal impingement between 2011 and 2017 were identified using the Major League Baseball's Health and Injury Tracking System. A separate player usage data set was used to determine workload. The authors compared workload variables (days of rest, innings pitched, and batters faced per game) between each of 4 injury-exposure groups (pitchers with documented internal impingement <2, <6, <12, and >12 weeks after a game) and a control group of pitchers with no internal impingement using Student t tests or Mann-Whitney U tests. In a within-pitcher paired analysis of the injury groups, the workload variables during 3 acute periods (<2, <6, and <12 weeks preinjury) were compared with the baseline values (>12 weeks preinjury).

Results

Overall, there were 624 professional baseball pitchers diagnosed with internal impingement during the study period. Compared with pitcher games (n = 213,964), pitchers in all 4 injury-exposure groups had significantly more innings pitched per game (P ≤ .003 for all) and faced significantly more batters per game (P < .001 for all). There were significantly more starting pitchers in each of the injury-exposure groups when compared with the controls (P < .001 for all). However, when comparing acute and baseline workloads in the pitchers diagnosed with internal impingement, there were no significant differences in the number of innings pitched, batters faced, or days of rest.

Conclusion

This analysis revealed significantly greater pitcher workload and percentage of starting pitchers in professional baseball players diagnosed with internal impingement when compared with healthy controls. However, this injury did not seem to be associated with an acute increase in workload.

Measuring the Average Peak Timing of Kinematic Variables in Youth and Adolescent Baseball Pitchers

Background

Previous studies have examined the timing of peak kinematic variables during the pitching cycle in high school, collegiate, and professional pitchers. These same variables have been studied less in younger populations.

Purpose

To determine whether youth and adolescent baseball pitchers will experience peaks in certain kinematic variables at different times throughout the pitching cycle compared to professional/collegiate pitchers.

Study Design

Cross-sectional, descriptive study.

Methods

Twenty-four participants were recruited for testing consisting of five recorded pitches using 3-Dimensional VICON® motion analysis system. The maximum values and timing of the peak kinematic variables were averaged across all trials using VICON Polygon® data analysis software. These values were recorded as percentages of the pitching cycle, defined from foot contact (0%) to ball release (100%). The following variables were examined: shoulder external rotation range of motion, shoulder internal rotation velocity, trunk rotation range of motion, trunk rotation velocity, pelvic rotation velocity, and stride length. Descriptive outcomes were calculated and results were compared to previous studies examining the same variables in collegiate and professional pitchers.

Results

Twenty-four male participants (mean age 12.75 years, SD ± 2.02) were included in the study. Mean and standard deviations were identified for peak kinematic variables of shoulder external rotation ROM (158.71°, ±9.32), shoulder internal rotation velocity (92.26 rad/sec, ±19.29), trunk rotation velocity (15.94 rad/sec, ±1.68), trunk rotation ROM (23.57°, ±8.14), and average stride length (81.97% height ±4.57). Additionally, mean and standard deviations of peak kinematic variables were expressed as percentages to reflect when they occurred in the pitching cycle and included trunk rotation ROM (8.45%, ±12.72), pelvic rotation velocity (33.26%, ±16.42), trunk rotation velocity (41.59%, ±9.27), shoulder external rotation ROM (71.34%, ±6.61), and shoulder internal rotation velocity (86.93%, ±6.45).

Conclusion

The sequential order of each variable was similar in youth and adolescents in comparison to collegiate and professional pitchers. However, the timing of each variable within the pitching cycle occurred approximately 10% earlier in the younger pitchers. The findings suggest differences in pitching mechanics exist between younger and more experienced populations.

Level of Evidence

Level 3.

Hidden Pitches in Major League Baseball: What Are the Injury Implications of These Often Overlooked Pitches?

Background

Pitch counts are tightly monitored in Major League Baseball (MLB). Hidden pitches-including warm-up pitches before and between innings and pitches before the starting/relieving pitcher's appearance in a game-are not as closely monitored.

Purpose/Hypothesis

To report the number of hidden pitches thrown per game and over the course of a season for a single organization. We hypothesized that players who threw more hidden pitches would be at an increased risk of injury compared with those who threw fewer hidden pitches.

Study Design

Case-control study; Level of evidence, 3.

Methods

All pitchers who played for a single MLB organization in the 2021 season were included. Hidden pitches, in-game pitches, and total pitches thrown during all games in the season were recorded. Injuries to these pitchers were also recorded. Players were defined as having an injury if they spent any time on the injured list.

Results

Overall, 137 pitchers were included, 66 (48%) of whom sustained an injury and were placed on the IL during the 2021 season (mean time on IL, 53.6 ± 45.6 days). Of the 66 players who sustained an injury, 18 (27.3%) sustained an elbow injury, while 12 (18.2%) sustained a shoulder injury. Only 1 player sustained an ulnar collateral ligament tear. When comparing hidden pitches, in-game pitches, and total pitches between pitchers who sustained an injury and those who did not, there were no significant differences between groups (P = .150; P = .830; and P = .377, respectively). On average, hidden pitches made up 45.4% of the total number of pitches thrown during the course of the season. When evaluating the number of hidden pitches as a percentage of the total number of pitches thrown in a season, there was no significant difference between pitchers who sustained an injury and those who did not (P = .654).

Conclusion

MLB pitchers who sustained an injury did not throw more hidden pitches than those who did not sustain an injury. Larger scale studies are needed to confirm the results of this single-team study.

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.

Personalized Injury Reduction Strategies in Sports Medicine: Lessons Learned from Advances in Breast Cancer Treatment: A Clinical Commentary

Background

Injury rates across sport have risen over the past twenty years, despite increased efforts in training and injury prevention. The rise in injury rates suggest that current approaches to estimating injury risk and risk management are not effective. One factor limiting progress is the inconsistency in screening, risk assessment, and risk management strategies to guide injury mitigation approaches.

Clinical Question

How can sports physical therapists identify and apply lessons learned from other healthcare fields to improve athlete injury risk and risk management strategies?

Key Results

Breast cancer mortality has consistently decreased over the last 30 years, largely attributed to advances in personalizing the prevention and treatment strategies which include modifiable and non-modifiable factors when assessing risk, the transition to personalized medicine, and the systematic approach used to investigate individual risk factors. Three critical phases have facilitated the identification and importance of individual risk factors and developing targeted, personalized strategies for breast cancer risk including: 1) Establishing the potential relationship between factors and outcomes; 2) Prospectively investigate the strength and direction of the relationship; 3) Investigating if intervening on identified factors alters prognosis.

Clinical Application

Applying lessons learned from other healthcare fields could improve shared decision making between the clinician and athlete concerning risk assessment and management. Examples include calculating only non-modifiable risk, creating individualized screening schedules based on risk assessment, or calculating the influence of each intervention on the athlete's injury risk. A systematic approach to identify and intervene on risk is needed to improve athlete outcomes.

Relationships Among Shoulder Rotational Strength, Range of Motion, Pitching Kinetics, and Pitch Velocity in Collegiate Baseball Pitchers

ABSTRACT

Cross, JA, Higgins, AW, Dziuk, CC, Harris, GF, and Raasch, WG. Relationships among shoulder rotational strength, range of motion, pitching kinetics, and pitch velocity in collegiate baseball pitchers. J Strength Cond Res 37(1): 129-135, 2023-Throwing shoulder injuries are the most common type of injury experienced by baseball pitchers. Weakness in the shoulder musculature and insufficient throwing arm range of motion are both risk factors for developing a shoulder injury. The goal of this study was to determine correlations among shoulder rotational strength, range of motion, pitching kinetics, and pitch velocity in collegiate pitchers. Thirteen uninjured male college pitchers were evaluated. Clinical measures included shoulder internal and external rotation range of motion, peak isokinetic internal and external rotator strength, and peak isometric internal and external rotator strength. Three-dimensional biomechanics were assessed as subjects threw from an indoor pitching mound to a strike zone net at regulation distance. Pearson's correlations were used to assess the associations among the clinical measures and throwing metrics. Five significant correlations were found between peak shoulder compressive force and strength, and 4 significant correlations were found between pitching velocity and strength ( p < 0.05). No significant correlations were found between range of motion and pitching kinetics or velocity. Our results suggest that as shoulder rotational strength increases, the peak shoulder compressive force and pitch velocity both increase. Knowledge of relationships between strength metrics and pitching biomechanics may allow for improved strength training routines with the goal of increasing velocity without increasing injury risk.

Risk Factors for Glenohumeral Internal Rotation Deficit in Adolescent Athletes: A Comparison of Overhead Sports and Non-overhead Sports

Background A glenohumeral internal rotation deficit (GIRD) occurs in baseball players due to the repetitive pitching motion. However, few reports have addressed associations between GIRD and sports other than baseball. In this study, we investigated whether GIRD occurs in adolescent athletes playing overhead sports other than baseball, and also, the risk factors that cause GIRD in these sports were examined. Methods A total of 214 junior high school athletes who had undergone medical checks were evaluated. Seventy-five athletes playing sports requiring overhead motions were classified into the overhead sports group (39 tennis, 18 handball, 12 badminton, and 6 softball players). Eighty athletes participating in sports requiring the use of the upper limbs but not requiring frequent overhead motions were classified into the non-overhead sports group (31 kendo, 20 fencing, 19 basketball, and 10 table tennis players); 59 athletes who mainly did not use an upper limb were classified into the contact sports group (22 judo, 15 wrestling, 13 soccer, and 9 rugby football players). The range of shoulder motion (internal rotation, external rotation, and total arc), background factors, general laxity, and flexibility of the lower body were compared among the three groups. Results Thirty-four (16%) of 214 players were classified as having GIRD (internal rotation deficit >15°). Significantly more athletes had GIRD in the overhead sports group than in the other groups (p=0.007). The internal rotation deficit was significantly worse in the overhead sports group than in the other groups (p=0.006, p=0.02, respectively). Background factors, general laxity, and lower body flexibility did not differ significantly among the groups. Conclusion The sole risk factor for GIRD was participating in any sport that required overhead movements. Thus, not only baseball players, but also other athletes who participate in sports requiring overhead movements should receive correct information to prevent GIRD.

Relationship of Subtalar Joint Range of Motion to Ankle Injuries in NBA G League and Collegiate Basketball Players

BACKGROUND

This study sought to determine whether range of motion (ROM) of the ankle and subtalar joint complex (STJ) is correlated with ankle injuries in National Basketball Association (NBA) G-league and collegiate basketball players to identify an at-risk population that may benefit from participation in an ankle injury prevention program.

METHODS

This prospective cohort study encompassed 103 player-seasons (68 collegiate, 35 NBA G-League). Patient demographics, passive ankle and STJ range of motion measurements, anterior drawer, and talar tilt tests were collected at preseason physicals along with plain radiographs. Subtalar eversion and inversion measurements were added to assess the Combination Motion (CM) of the STJ and subtracted to calculate the Subtalar Difference (SD). We defined the ratio of CM to SD as Subtalar Mobility Index (SMI=CM/SD).

RESULTS

Twenty-one ankle injuries occurred with 10 405 player exposures yielding an incidence of 2.11/1000 exposures, resulting in 113 days of missed playing time. No direct measures of ankle, subtalar, or combined motion were associated with risk of injury, rejecting our original hypothesis that increased STJ ROM would predispose to ankle injuries. However, we did find that athletes with CM >16 degrees in combination with either SD <6 degrees (P = .025) or SMI >3.75 (P = .032) were nearly 3 times more likely to have an ankle injury (3.14 vs 2.97, respectively).

CONCLUSION

Using the predictive subtalar mobility thresholds found in this study may help identify at-risk players that may benefit from targeted ankle injury prevention programs.

LEVEL OF EVIDENCE

Level II, prospective cohort study.

Shoulder Range of Motion Measurements and Baseball Elbow Injuries: Ambiguity in Scientific Models, Approach, and Execution is Hurting Overhead Athlete Health

Elbow injuries are a significant and increasing issue in baseball. Elbow injuries account for 16% of all injuries sustained at the professional level and collegiate level. Because of the continued rise in injury rates, loss of performance value, and medical burden, sports medicine clinicians have attempted to research the causes underlying this injury epidemic in an attempt to help mitigate baseball elbow injuries. Shoulder range of motion (ROM) is the most researched clinical metric related to elbow injuries in baseball and has the greatest consensus as a viable prognostic factor specifically for medial elbow injury. Shoulder ROM is easy to measure, can be modified through stretching and manual therapy interventions, and can be easily assessed during preseason screening throughout all baseball levels. Despite a large number of studies and the widespread use of shoulder ROM in injury risk screening, current findings are unclear as to whether there is a true cause-effect relation with baseball elbow injuries. We argue that the conflicting findings revolving around the value of shoulder ROM measurements associated with baseball elbow injuries are the result of 4 gaps in the research approaches implemented to date: ambiguous research questions, mixed study populations, statistical models used, and shoulder ROM methodology. Specifically, there is a mismatch of methods, statistical models, and conclusions such as (1) investigating the association (i.e., correlation) between shoulder ROM measurements and injury and (2) investigating the cause-effect relation of shoulder ROM to baseball injuries. The purpose of this article is to detail the required scientific steps to evaluate whether preseason shoulder ROM is a potential causal factor for pitching elbow injury. We also provide recommendations to allow for future causal inferences to be made between shoulder ROM and elbow injury. This information will ultimately assist in informing clinical models of care and decision making for baseball throwers.

Assessing the Association of Shoulder Pain Risk with Physical Fitness in Badminton Players at National Tournament Level

Background: Shoulder pain which affects sports performance and activities of daily life, is a common musculoskeletal problem experienced by badminton players. Objectives: This study aimed to identify the association of shoulder pain with physical fitness in elite university badminton players participating in the national tournament via medical check-ups. Methods: Physical fitness evaluations were performed among fifty-two 18 - 22 years old university badminton players participating in the national tournament. Handgrip strength, heel buttock distance, angle of straight leg raise, single leg stance, shoulder range of motion, and trunk range of motion were assessed. The prevalence of present shoulder pain was described. Multivariable logistic regression was used to examine the association of present shoulder pain with physical fitness. Results: Sixteen badminton players (30.8%) sustained present shoulder pain related to badminton. Dominant trunk rotation (adjusted OR: 0.91, 95% CI: 0.84 - 0.99, P-value = 0.028) and single leg stance of the nondominant leg (adjusted OR: 0.97, 95% CI: 0.94 - 1.00, P-value = 0.048) were significantly associated with the presence of present shoulder pain. Conclusions: Decreased trunk rotation and deficit in single-leg stance balance might be potential risk factors associated with physical fitness for shoulder pain in university badminton players at national tournament level. These findings can help draw the attention of badminton coaches, players, and team members to facilitate physical fitness promotion for badminton pain/injury prevention.

Development of an Injury Burden Prediction Model in Professional Baseball Pitchers

Background

Baseball injuries are a significant problem and have increased in incidence over the last decade. Reporting injury incidence only gives context to rate but not in relation to severity or injury time loss.

Hypothesis/Purpose

The purpose of this study was to 1) incorporate both modifiable and non-modifiable factors to develop an arm injury burden prediction model in Minor League Baseball (MiLB) pitchers; and 2) understand how the model performs separately on elbow and shoulder injury burden.

Study Design

Prospective longitudinal study.

Methods

The study was conducted from 2013 to 2019 on MiLB pitchers. Pitchers were evaluated in spring training arm for shoulder range of motion and injuries were followed throughout the season. A model to predict arm injury burden was produced using zero inflated negative binomial regression. Internal validation was performed using ten-fold cross validation. Subgroup analyses were performed for elbow and shoulder separately. Model performance was assessed with root mean square error (RMSE), model fit (R2), and calibration with 95% confidence intervals (95% CI).

Results

Two-hundred, ninety-seven pitchers (94 injuries) were included with an injury incidence of 1.15 arm injuries per 1000 athletic exposures. Median days lost to an arm injury was 58 (11, 106). The final model demonstrated good prediction ability (RMSE: 11.9 days, R2: 0.80) and a calibration slope of 0.98 (95% CI: 0.92, 1.04). A separate elbow model demonstrated weaker predictive performance (RMSE: 21.3; R2: 0.42; calibration: 1.25 [1.16, 1.34]), as did a separate shoulder model (RMSE: 17.9; R2: 0.57; calibration: 1.01 [0.92, 1.10]).

Conclusions

The injury burden prediction model demonstrated excellent performance. Caution should be advised with predictions between one to 14 days lost to arm injury. Separate elbow and shoulder prediction models demonstrated decreased performance. The inclusion of both modifiable and non-modifiable factors into a comprehensive injury burden model provides the most accurate prediction of days lost in professional pitchers.

Level of Evidence

2.

The relationship between scapular position and glenohumeral rotational range of motion in high school baseball players

BACKGROUND

Past research indicated that scapular malposition is related to the glenohumeral internal rotation deficit (GIRD). However, there is no research examining the effect of throwing-related pain on this relationship. This study investigated the relationship between scapular position and range of motion (ROM) and compared the difference in this relationship between with and without throwing-related pain.

METHODS

Forty male baseball players in high school were recruited for this study. The existence and degree of throwing-related pain were obtained from a questionnaire. Participants were divided into 2 groups according to the presence or absence of the pain. Glenohumeral internal and external rotation ROM (abduction internal rotation angle and abduction external rotation angle [ABER], respectively) were measured using a digital inclinometer. The pectoralis minor muscle length was measured using a vernier caliper and scapula index, which indicated the scapular position, measured using a measuring tape. All these measurements were taken on both dominant and nondominant sides. The GIRD and total motion arc (TMA) deficit were calculated from the ROM measurements. Groups were compared using a mixed-model analysis of variance.

RESULTS

There was a significant interaction between group and ABER dominance. Other variables were not seen as the interaction effect. There was a significant positive correlation between the scapula index and TMA (r = 0.47, P = .02) and a negative correlation between the scapula index and GIRD (r = -0.65, P < .01) in the dominant side of the pain group. In addition, in the nondominant side of the pain group, the scapula index and ABER were significantly correlated (r = 0.43, P = .04).

CONCLUSIONS

The results of this study indicate that the scapular position is associated with the glenohumeral ROM in high school baseball players. In addition, this study demonstrated that the scapular internally rotated position was correlated with the GIRD and TMA deficit in high school baseball players who had throwing-related pain. On the other hand, the scapular externally rotated position was correlated with increased ABER, mainly in the pain-free baseball players or on the nondominant side. These results indicated that the scapular position might affect the glenohumeral rotational ROM in high school baseball players.

Predicting the Clean Movement Technique in Crossfit® Athletes Using an Optimal Upper-Limb Range of Motion: A Prospective Cohort Study

BACKGROUND

The aim of this study was to determine the optimal upper-limb range of motion (ROM) profile for the catch phase of the clean movement (CPCM) and to identify the key ROMs for performing the CPCM in CrossFit^® athletes.

METHODS

A prospective cohort study of twenty CrossFit^® athletes aged 20-36 years was conducted. Data were collected regarding age, anthropometrics, CrossFit^® training experience and upper-limb ROM. The ROM was measured using the ROM-SPORT method. After 7 months, athletes performed a clean movement with a load of 80% one repetition maximum. A Bayesian Student's t-analysis, binary logistic regression analysis and Receiver Operating Characteristic analysis were performed.

RESULTS

The optimal upper-limb ROM profile that predicted correct CPCM performance was 78° in shoulder extension, 173° in shoulder flexion, 107° in shoulder external rotation, 89° in shoulder internal rotation, 153° in elbow flexion, 99° in elbow pronation and 92° in wrist extension (area under the curve ≥ 651; positive predictive value ≥ 80%). Shoulder external rotation, elbow pronation and wrist extension were found to be the most important ROMs for the efficient and safe performance of CPCM (area under the curve ≥ 854; positive predictive value ≥ 85.7%).

CONCLUSION

The upper-limb ROM profile is associated with proper clean performance. Further studies are warranted to determine whether improving flexibility on upper-limb ROM may improve proper clean movement performance.

Active range of motion of the shoulder: a cross-sectional study of 6635 subjects

Background

Normative data for passive range of motion are well established, but daily living is comprised of active motion. The purpose of this study was to establish normative values for active range of motion of the shoulder across age, sex, and arm. Our hypotheses were that active range of motion of the shoulder (1) decreases with age group, (2) differs between males and females, and (3) differs between the right arm and left arm.

Methods

Shoulder active range of motion was captured with an eight-camera markerless motion capture system. Data were collected for a heterogenous sample of 6635 males and females of all ages. For each subject, 6 shoulder motions were collected with maximum values measured: external rotation, internal rotation, flexion, extension, abduction, and horizontal abduction. Three-way repeated measures analyses were performed, with 2 between-subject factors (age group and sex) and 1 within-subject factor (arm). The unadjusted threshold for statistical significance was α = 0.05.

Results

External rotation decreased with age (approximately 10° decrease from below 30 years to above 60 years). External rotation was approximately 5° greater in the right arm, whereas internal rotation was approximately 5° greater in the left arm. Flexion decreased with age (approximately 15° decrease from below 20 years to above 60 years). For age groups from 10 to 59 years, extension and horizontal abduction were approximately 5° to 10° greater in females than males. Abduction was greater for females than males. Abduction was also greater in younger people (aged 10-29 years) than older people.

Conclusion

In general, active range of motion of the shoulder decreases with age. Sex (male/female) and arm side (right/left) also influence shoulder range of motion.

Increased external rotation related to the soft tissues is associated with pathologic internal impingement in high-school baseball players

BACKGROUND

Changes in soft-tissue structures such as anterior laxity and posterior tightness are thought to contribute to the development of pathologic internal impingement in baseball players. Although side-to-side differences in shoulder rotational range of motion (ROM) is commonly used in clinical practice to quantify the soft-tissue changes, the ROM does not accurately reflect the soft-tissue changes because the ROM is affected not only by the soft tissues, but also by the bone. Increased retroversion of the humeral head is often observed in the dominant shoulder of throwing athletes. The purpose of this study was to determine the relationship between the soft-tissue-related (STR) ROM and pathologic internal impingement in baseball players.

METHODS

Bilateral humeral retroversion and ranges of glenohumeral external rotation (ER) and internal rotation (IR) were investigated in 81 high-school baseball players. The players were divided into two groups: the internal impingement group (19 players) and the control group (62 players). Humeral retroversion was measured using the ultrasound-assisted technique to assess the bone-related ER and IR. The STR ER and IR were defined as subtracting the amount of humeral retroversion from the measured ER and IR.

RESULTS

The side-to-side difference (throwing shoulder - nonthrowing shoulder) in humeral retroversion showed no significant difference between the internal impingement group (6° ± 10°) and control group (11° ± 11°) (P = .064). The side-to-side difference in STR ER was significantly greater in the internal impingement group (12° ± 12°) than that in the control group (1° ± 14°) (P = .002). No significant difference was observed in the side-to-side difference in STR IR between the internal impingement group (-7° ± 16°) and control group (-5° ± 15°) (P = .696). Pathologic internal impingement was significantly associated with the side-to-side difference of STR ER (odds ratio, 1.06 for increase of 1°; 95% confidence interval, 1.02-1.11; P = .008).

CONCLUSION

In high-school baseball players, the increased STR ER in the throwing shoulder may be associated with pathologic internal impingement. An increase of 10° in side-to-side difference in STR ER would increase the risk of pathologic internal impingement by 1.8 times.

Including Modifiable and Nonmodifiable Factors Improves Injury Risk Assessment in Professional Baseball Pitchers

OBJECTIVES

To (1) evaluate an injury risk model that included modifiable and nonmodifiable factors into an arm injury risk prediction model in Minor League Baseball (MiLB) pitchers and (2) compare model performance separately for predicting the incidence of elbow and shoulder injuries.

DESIGN

Prospective cohort.

METHODS

A 10-year MiLB injury risk study was conducted. Pitchers were evaluated during preseason, and pitches and arm injuries were documented prospectively. Nonmodifiable variables included arm injury history, professional experience, arm dominance, year, and humeral torsion. Modifiable variables included BMI, pitch count, total range of motion, and horizontal adduction. We compared modifiable, nonmodifiable, and combined model performance by R2, calibration (best = 1.00), and discrimination (area under the curve [AUC]; higher number is better). Sensitivity analysis included only arm injuries sustained in the first 90 days.

RESULTS

In this study, 407 MiLB pitchers (141 arm injuries) were included. Arm injury incidence was 0.27 injuries per 1000 pitches. The arm injury model (calibration 1.05 [0.81-1.30]; AUC: 0.74 [0.69-0.80]) had improved performance compared to only using modifiable predictors (calibration: 0.91 [0.68-1.14]; AUC: 0.67 [0.62-0.73]) and only shoulder range of motion (calibration: 0.52 [0.29, 0.75]; AUC: 0.52 [0.46, 58]). Elbow injury model demonstrated improved performance (calibration: 1.03 [0.76-1.33]; AUC: 0.76 [0.69-0.83]) compared to the shoulder injury model (calibration: 0.46 [0.22-0.69]; AUC: 0.62 [95% CI: 0.55, 0.69]). The sensitivity analysis demonstrated improved model performance compared to the arm injury model.

CONCLUSION

Arm injury risk is influenced by modifiable and nonmodifiable risk factors. The most accurate way to identify professional pitchers who are at risk for arm injury is to use a model that includes modifiable and nonmodifiable risk factors. J Orthop Sports Phys Ther 2022;52(9):630-640. Epub: 9 July 2022. doi:10.2519/jospt.2022.11072.

Initial kinematic chain injuries increase hazard of subsequent arm injuries in professional baseball pitchers

BACKGROUND

Currently, there are few studies that have evaluated the relationship between a lower extremity or trunk injury (kinematic chain) and subsequent arm injury. The purpose of this study was (1) to investigate the relationship between initial kinematic chain (lower extremity or trunk) injury and subsequent arm injury; and (2) to investigate the relationship between initial shoulder or elbow injury and subsequent arm injury.

METHODS

A 7-year prospective injury risk study was conducted with Minor League Baseball pitchers. Pitches, pitching appearances, athlete exposures (AEs), and arm injuries (≥1-day time loss) were documented throughout the season. Cox survival analyses with 95% confidence intervals (95% CIs) were performed. Confounders controlled for included age, body mass index, arm dominance, pitching role, previous arm injury, number of pitching appearances, and seasonal pitch load.

RESULTS

A total of 297 pitchers participated (total player days = 85,270). Arm injury incidence was 11.4 arm injuries/10,000 AEs, and kinematic chain incidence was 5.2 injuries/10,000 AEs. Pitchers who sustained a kinematic chain injury demonstrated a greater hazard (2.6 [95% CI: 1.2, 5.6], P = .019) of sustaining an arm injury. Pitchers who sustained an initial shoulder injury demonstrated a greater hazard (9.3 [95% CI: 1.1, 83], P = .047) of sustaining a subsequent shoulder or elbow injury compared with pitchers who sustained an initial elbow injury.

CONCLUSIONS

Pitchers who sustained an initial lower extremity or trunk injury demonstrated an increased subsequent arm injury hazard compared with pitchers who did not. Pitchers who sustained an initial shoulder injury demonstrated a greater hazard of sustaining a subsequent arm injury compared with pitchers who sustained an initial elbow injury. However, this secondary analysis should be interpreted with caution. Clinicians should monitor risk with workload accumulation, which may be related to pitching compensatory strategies in a fatigued state. Pitchers who sustain a shoulder injury should be evaluated and perform both shoulder and elbow rehabilitation strategies before return to sport.

Glenohumeral Internal Rotation Deficit in the Adolescent Overhead Athlete: A Systematic Review and Meta-Analysis

OBJECTIVE

The objective of this review was to investigate the average glenohumeral internal rotation deficit (GIRD) in the dominant arm of adolescent overhead athletes and to examine the association with shoulder and elbow injuries.

DESIGN

Systematic review and meta-analysis.

SETTING

MEDLINE, Embase, and PubMed were searched from inception to August 1, 2020.

PARTICIPANTS

Adolescent overhead athletes with glenohumeral range of motion (ROM) measurements.

INTERVENTIONS

Nonoperative treatments of GIRD.

MAIN OUTCOME MEASURES

Glenohumeral ROM measurements comparing the dominant and nondominant extremities were pooled in a meta-analysis.

RESULTS

Twenty-five studies were included in this review, which involved 2522 overhead athletes. Pooled internal rotation (IR) deficit of the dominant arm was 9.60° (95% confidence interval [CI] 7.87°-11.32°, P < 0.00001), with an external rotation (ER) gain of 6.78° (95% CI 4.97°-8.59°, P < 0.00001) and a total ROM (TROM) deficit of 1.78° (95% CI -0.70° to 4.26°, P = 0.16). The association between GIRD and shoulder or elbow injury was not clearly defined. Two studies reported treatment, and both used nonoperative treatment in the form of physiotherapy and sleeper stretches.

CONCLUSIONS

The adolescent overhead athlete has roughly 10° of IR deficit in their dominant arm, accompanied by nearly 7° of ER gain, with similar ROM measurements for injured and uninjured athletes. Those with pathological GIRD have a greater degree of IR deficit, but without an accompanying compensatory increase in ER, leading to a TROM deficit of nearly 15°. Surgical treatment in the absence of other indications is rare, whereas physiotherapy and sleeper stretches remain the first-line treatment.

GIRD syndrome in male handball and volleyball players: Is the decrease of total range of motion the turning point to pathology?

BACKGROUND

Adaptations in glenohumeral range of motion may affect overhead athletes and lead to shoulder pathologies.

OBJECTIVE

The purpose of this study was to evaluate glenohumeral internal rotation deficit (GIRD) and postero-superior impingement among male handball and volleyball players and the relationship between these pathologies and training level (amateur vs. professional), position (attack vs. no attack), experience (> 5 years vs. < 5 years) and sports.

METHODS

Sixty-seven handball players and 67 volleyball players with a mean age of 25 [± 5] years were included. The range of motion including external and internal rotation in 90∘ abduction of the dominant and non-dominant shoulder was measured of each examined athlete. Visual analogue scale, disabilities of the shoulder and hand score, constant score and subjective shoulder value were recorded. The athletes were examined for postero-superior impingement and abduction force was measured with an isokinetic dynamometer.

RESULTS

Internal rotation was significantly lower and external rotation was significantly greater in the dominant arm for both sports. 72% presented with GIRD. GIRD was more prevalent in athletes active for > 5 years (odds ratio (OR) 3), in those training > 3 times per week (OR 1.4) and in handball players (OR 2.7). 24% presented with postero-superior impingement. Players active for > 5 years (OR 1.22), professionals (OR 1.14), volleyball players (OR 1.19), offensive players (OR 2.2) and athletes with GIRD > 10∘ (OR 1.5) showed a higher prevalence of postero-superior impingement.

CONCLUSION

GIRD is a common phenomenon in handball and volleyball players. Offensive players are frequently suffering from postero-superior impingement. GIRD > 10∘ leads in nearly 75% of the athletes to a decrease of total range of motion and a high rate of postero-superior impingement. Thus, a decreased range of motion seems to be the turning point from adaptation to pathology. Therefore, regular controls of range of motion and countermeasures by means of stretching the posterior shoulder joint should be integrated in the training content.

Is early trunk rotation really hazardous for shoulder biomechanics in baseball throwing?

BACKGROUND AND HYPOTHESIS

Early trunk rotation (ETR), which is a unique kinematics of the trunk that occurs during baseball throwing, is thought to be related to shoulder injuries. Pelvic rotation is a confounder when studying the effects of trunk rotation on shoulder biomechanics. The purpose of this study was to understand the "pure" effects of trunk rotation on shoulder biomechanics, with pelvic rotation under control. Our hypotheses were as follows: (1) throwers with ETR have a different shoulder kinematics pattern compared with throwers without ETR; (2) throwers with ETR have a lower ball speed performance than do throwers without ETR; and (3) throwers with ETR have a greater value of shoulder forces and moments, which may increase risks of shoulder injury, than do throwers without ETR.

METHODS

Fifty-seven elite throwers were enrolled and divided into 2 groups (non-ETR and ETR) using an outdoor motion analysis. Several kinematics and kinetics parameters of the shoulder were analyzed and compared between the 2 groups.

RESULTS

Ball velocity was faster in the non-ETR group (127 km/h) compared with the ETR group (120 km/h). The shoulders of throwers in the ETR group showed pathokinematics of "horizontal adduction lag" and "dropped elbow." The increases in maximal posterior force, inferior force, horizontal abduction moment, and vertical adduction moment were 9.2%, 13.6%, 21.3%, and 24.3%, respectively, in the shoulders of throwers in the ETR group. These results indicate that ETR may be hazardous for the throwing shoulder. With lower ball velocity and higher shoulder joint loading, ETR is not a proper pitching pattern for kinetic energy transfer.

CONCLUSION

Improper pitching mechanics among baseball throwers, such as ETR, may result in higher shoulder joint loading and increased risk of shoulder injuries. When treating throwers with shoulder injuries, it is important not only to address shoulder anatomy and pathology but also to understand the possible pathomechanics and pathogenesis of the shoulder caused by ETR. Furthermore, special training programs focusing on trunk flexibility and core muscle strengthening should be implemented to prevent ETR and decrease the risk of shoulder injuries. Motion analysis is useful for the screening and early detection of improper pitching mechanics in throwers.

Athletic Shoulder Test Differences Exist Bilaterally in Healthy Pitchers

Background

There is a lack of valid and reliable tests that assess upper extremity strength and function for rehabilitation and injury prevention purposes in throwing athletes. The Athletic Shoulder (ASH) test has been proposed as a reliable measure of shoulder strength, but has not yet been studied in baseball pitchers.

Hypothesis/Purpose

The purpose of this study was to establish values for healthy baseball pitchers performing the ASH test, compare those values with other common tests of shoulder strength and function, and compare ASH test performance bilaterally. It was hypothesized that the dominant arm would perform significantly better on the ASH test compared to the non-dominant arm. A secondary purpose of the study was to evaluate if ASH test performance was related to fastball velocity in baseball pitchers. It was hypothesized that ASH test performance would positively correlate with fastball velocity.

Study Design

Cross-Sectional Study.

Methods

College and high school baseball pitchers were recruited to complete shoulder range of motion (ROM), isokinetic shoulder strength, and isometric shoulder strength testing using the ASH test. The ASH test was used to assess force production as a proxy for strength bilaterally at four levels of shoulder abduction (0°, 90°, 135°, and 180°), using a force plate. Approximately one-week later subjects returned for a bullpen session where fastball velocity was recorded with a radar gun. Bilateral differences in passive ROM, isokinetic, and isometric shoulder strength were examined using paired t-tests while linear relationships between isometric shoulder strength and fastball velocity were assessed using Pearson correlations.

Results

Thirty-five healthy pitchers participated in the study (19.7 ± 1.8 years). Pitchers demonstrated significantly greater isometric shoulder strength at the 90° and 135° abduction positions with the throwing arm compared to the non-throwing arm. Pitchers also demonstrated commonly observed musculoskeletal adaptations in the throwing arm such as increased passive external rotation, decreased passive internal rotation, and greater internal and external rotator strength during isokinetic testing. Peak force production during the ASH test was not related to fastball velocity.

Conclusion

The ASH test is capable of detecting bilateral shoulder strength adaptations commonly observed in other clinical tests in healthy pitchers. Pitchers demonstrated greater isometric peak force during the ASH test at levels of shoulder abduction similar to those observed in pitching. While these results may be intriguing for clinical use, peak force from the ASH test was not correlated to fastball velocity in pitchers, and therefore should be used with caution for predictions in this realm.

Level of Evidence

2.

Clinical Relevance

A need exists for objective measures of shoulder strength for rehabilitation and injury risk monitoring in throwing athletes that are easy to administer, have high reliability and validity, and provide minimal re-injury risk to athletes recovering from injury.

What is known about the subject

Data from the ASH test has been published previously in non-throwing athletes and was shown to be valid and reliable in that group. However, the test has not been explored widely in throwing athletes who are known to have significant musculoskeletal adaptations to the throwing shoulder.

What this study adds to existing knowledge

The results from this study confirm that the ASH test is sensitive enough to detect the adaptations that are present in the healthy throwing athlete's shoulder. Due to the prior proven validity and reliability and these results, the test can be used to monitor throwing arm strength and function during rehabilitation or as a pre/intra-season screening tool to help describe arm health.

Age-related differences in glenohumeral internal rotation deficit, humeral retrotorsion angle, and posterior shoulder tightness in baseball players

BACKGROUND

Glenohumeral internal rotation deficit is generally recognized as a risk factor for throwing disability in baseball players. However, the pathology, timing of onset, role in the onset of humeral retrotorsion angle (HTA) and soft tissue extensibility (STE), and the relationship with age remain unclear. Therefore, the purpose of this cross-sectional study was to investigate age-related glenohumeral internal rotation deficit, HTA, and STE in Japanese baseball players and determine whether these factors correlate with throwing disability.

METHODS

Participants were 172 male baseball players divided into a symptomatic group (n = 68) and an asymptomatic group (n = 104). The mean age at examination was 15.4 ± 3.2 (range, 8-22) years. Measurement items were range of motion of bilateral internal and external rotation at 90° abduction (2ndIR and 2ndER, respectively), bilateral HTA, and posterior shoulder muscle elasticity. Correlations of age, symptom, and dominance with these measurements were investigated, and significant bilateral differences in HTA and STE by age and symptom were analyzed.

RESULTS

HTA and 2ndER of the dominant side were significantly greater than those of the nondominant side in those over the age of 13 years in both the asymptomatic and symptomatic groups. In contrast, 2ndIR of the dominant side was significantly smaller than that of the nondominant side in those over the age of 13 years in both the asymptomatic and symptomatic groups. The difference in HTA between the dominant and nondominant sides increased and then plateaued at 12° after the age of 16 years. STE was observed only in the symptomatic group, and the value of STE was significantly greater in players aged >16 years compared with that in players aged <12 years (P = .001). Muscle elasticity did not differ significantly between sides and showed no correlation with STE.

CONCLUSIONS

The difference in HTA between the dominant and nondominant sides increased with age until 16 years old regardless of symptoms. STE in the dominant side was observed only in symptomatic baseball players after the age of 13 years and increased with age, plateauing around the age of 16 years. Posterior shoulder muscle elasticity was not indicated as a cause of STE.

Disabled Throwing Shoulder: 2021 Update: Part 2-Pathomechanics and Treatment

The purpose of this paper is to provide updated information for sports healthcare specialists regarding the disabled throwing shoulder (DTS). A panel of experts, recognized for their experience and expertise in this field, was assembled to address and provide updated information on several topics that have been identified as key areas in creating the DTS spectrum. Each panel member submitted a concise presentation on one of the topics within these areas, each of which were then edited and sent back to the group for their comments and consensus agreement in each area. Part two presents the following consensus conclusions and summary findings regarding pathomechanics and treatment, including (1) internal impingement results from a combination of scapular protraction and humeral head translation; (2) the clinically significant labral injury that represents pathoanatomy can occur at any position around the glenoid, with posterior injuries most common; (3) meticulous history and physical examination, with a thorough kinetic chain assessment, is necessary to comprehensively identify all the factors in the DTS and clinically significant labral injury; (4) surgical treatment should be carefully performed, with specific indications and techniques incorporating low profile implants posterior to the biceps that avoid capsular constraint; (5) rehabilitation should correct all kinetic chain deficits while also developing high-functioning, throwing-specific motor patterns and proper distribution of loads and forces across all joints during throwing; and (6) injury risk modification must focus on individualized athlete workload to avoid overuse. LEVEL OF EVIDENCE: V, expert opinion.

Disabled Throwing Shoulder 2021 Update: Part 1-Anatomy and Mechanics

The purpose of this article is to provide updated information for sports health care specialists regarding the Disabled Throwing Shoulder (DTS). A panel of experts, recognized for their experience and expertise in this field, was assembled to address and provide updated information on several topics that have been identified as key areas in creating the DTS spectrum. Each panel member submitted a concise presentation on one of the topics within these areas, each of which were then edited and sent back to the group for their comments and consensus agreement in each area. Part 1 presents the following consensus conclusions and summary findings regarding anatomy and mechanics, including: 1) The current understanding of the DTS identifies internal impingement, resulting from a combination of causative factors, as the final common pathway for the great majority of the labral pathoanatomy; 2) intact labral anatomy is pivotal for glenohumeral stability, but its structure does not control or adapt well to shear or translational loads; 3) the biceps plays an active role in dynamic glenohumeral stability by potentiating "concavity compression" of the glenohumeral joint; 4) the ultimate function of the kinetic chain is to optimize the launch window, the precise biomechanical time, and position for ball release to most effectively allow the ball to be thrown with maximum speed and accuracy, and kinetic chain function is most efficient when stride length is optimized; 5) overhead throwing athletes demonstrate adaptive bony, capsular, and muscular changes in the shoulder with repetitive throwing, and precise measurement of shoulder range of motion in internal rotation, external rotation, and external rotation with forearm pronation is essential to identify harmful and/or progressive deficits. LEVEL OF EVIDENCE: Level V, expert opinion.

The Clinician's Guide to Baseball Pitching Biomechanics

CONTEXT

Improper baseball pitching biomechanics are associated with increased stresses on the throwing elbow and shoulder as well as an increased risk of injury.

EVIDENCE ACQUISITION

Previous studies quantifying pitching kinematics and kinetics were reviewed.

STUDY DESIGN

Clinical review.

LEVEL OF EVIDENCE

Level 5.

RESULTS

At the instant of lead foot contact, the elbow should be flexed approximately 90° with the shoulder at about 90° abduction, 20° horizontal abduction, and 45° external rotation. The stride length should be about 85% of the pitcher's height with the lead foot in a slightly closed position. The pelvis should be rotated slightly open toward home plate with the upper torso in line with the pitching direction. Improper shoulder external rotation at foot contact is associated with increased elbow and shoulder torques and forces and may be corrected by changing the stride length and/or arm path. From foot contact to maximum shoulder external rotation to ball release, the pitcher should demonstrate a kinematic chain of lead knee extension, pelvis rotation, upper trunk rotation, elbow extension, and shoulder internal rotation. The lead knee should be flexed about 45° at foot contact and 30° at ball release. Corrective strategies for insufficient knee extension may involve technical issues (stride length, lead foot position, lead foot orientation) and/or strength and conditioning of the lower body. Improper pelvis and upper trunk rotation often indicate the need for core strength and flexibility. Maximum shoulder external rotation should be about 170°. Insufficient external rotation leads to low shoulder internal rotation velocity and low ball velocity. Deviation from 90° abduction decreases the ability to achieve maximum external rotation, increases elbow torque, and decreases the dynamic stability in the glenohumeral joint.

CONCLUSION

Improved pitching biomechanics can increase performance and reduce risk of injury.

SORT

Level C.

Throwing Injury Prevention Strategies with a Whole Kinetic Chain-Focused Approach

Purpose of Review

This review examines the relationship between the baseball pitching motion and the kinetic chain. The goal was to determine the underlying causes of a deficiency in throwing mechanics throughout a throwing motion, and to provide an evidence-based approach on how to prevent injuries caused by a lack of proper mechanics. In doing so, we sought to provide a warm-up strategy that can be added to every baseball player’s daily on-field routine that is tailored to each phase of the throwing motion.

Recent Findings

To help minimize the risk of injury to overhead throwing athletes, a thorough understanding of the throwing motion is critical. Throwing a ball places extreme stress on the body, notably the shoulder and elbow joints. With a clear understanding of the biomechanics of throwing, we can develop an injury prevention routine to minimize unnecessary stresses throughout the kinetic chain.

Summary

The throwing cycle is a complex motion that places various stresses throughout the thrower’s body, from the ankle to the core, and from the back to the shoulder and elbow. A thorough understanding of the mechanics of this motion, along with specific exercises to target the specific actions of each phase, may allow for throwers, regardless of their age and experience, to minimize injury risk.

The Thrower's Shoulder

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The thrower's shoulder has been a subject of great interest for many decades. Different theories have been proposed to clarify the pathophysiology, clinical presentation, and treatment options for this condition. In this review article, we summarize the relevant anatomy and pathophysiology and how these translate into signs, symptoms, and imaging findings. Also, a historical review of the treatment methodologies in the setting of an evolving concept is presented.

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The initial event in the cascade is thickening and contracture of the posteroinferior capsule resulting from repetitive tensile forces during the deceleration phase of throwing. This is known as "the essential lesion" and is clinically perceived as glenohumeral internal rotation deficit (GIRD), and a Bennett lesion may be found on radiographs.

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Change in the glenohumeral contact point leads to a series of adaptations that are beneficial for the mechanics of throwing, specifically in achieving the so-called "slot," which will maximize throwing performance.

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The complexity of the throwing shoulder is the result of an interplay of the different elements described in the cascade, as well as other factors such as pectoralis minor tightness and scapular dyskinesis. However, it is still unclear which event is the tipping point that breaks the balance between these adaptations and triggers the shift from an asymptomatic shoulder to a painful disabled joint that can jeopardize the career of a throwing athlete. Consequences are rotator cuff impingement and tear, labral injury, and scapular dyskinesis, which are seen both clinically and radiographically.

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A thorough understanding of the pathologic cascade is paramount for professionals who care for throwing athletes. The successful treatment of this condition depends on correct identification of the point in the cascade that is disturbed. The typical injuries described in the throwing shoulder rarely occur in isolation; thus, an overlap of symptoms and clinical findings is common.

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The rationale for treatment is based on the pathophysiologic biomechanics and should involve stretching, scapular stabilization, and core and lower-body strengthening, as well as correction of throwing mechanics, integrating the entire kinetic chain. When nonoperative treatment is unsuccessful, surgical options should be tailored for the specific changes within the pathologic cascade that are causing a dysfunctional throwing shoulder.

Effect of Weather and Game Factors on Injury Rates in Professional Baseball Players

BACKGROUND

Injury rates in baseball players of all ages are increasing. Identifying modifiable risk factors is paramount to implementing injury prevention programs.

PURPOSE/HYPOTHESIS

The purpose was to evaluate the influence of weather (temperature, humidity, atmospheric pressure, and heat index) and game factors (start time, duration, single vs doubleheader) on injury rates in professional baseball players. We hypothesized that colder temperatures would be associated with significantly more injuries per game.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

This was a retrospective database study. Two data sets were combined: 1 containing all injuries in Major and Minor League Baseball between 2011 and 2017 and 1 containing all games played in Major and Minor League Baseball during the same period to determine the number of injuries per game. Temperature, humidity, atmospheric pressure, and heat index were determined for each game using the data from the US Environmental Protection Agency. Additional game variables included the level of play, the turf type (natural vs artificial grass), the stadium type (open vs dome vs retractable), the game start time, the game duration, and whether the game was a doubleheader. Then, a multivariate analysis was conducted to determine which factors were associated with the number of injuries per game.

RESULTS

In total, our analysis included 33,587 injuries and 76,747 games. A total of 25,776 (33.6%) games contained an injury, and 41% of injuries occurred as multiples per game, with up to 9 injuries per game. The multivariate analysis identified significant associations between game duration and injuries per game (P < .001; effect size, 0.013) and the level of play and injuries per game (P < .001; effect size, 0.011). There were significant associations between the venue type (P < .001), the game start time (P < .001), humidity (P < .001), the turf type (P = .016), and barometric pressure (P = .031); however, the effect size for each was <0.001, suggesting that these factors are clinically unimportant. Our overall model produced an R² of 0.04, indicating that these variables only predicted 4% of the variance in injury risk.

CONCLUSION

In professional baseball, the weather is not associated with injury risk; however, game duration may contribute to injury risk.

How does the All-Star break affect injury rates in professional baseball?

Background

Injury rates in professional baseball players are increasing. It is unclear if the time of rest from the All-Star break affects injury risk.

Methods

Every professional baseball game (A-, A+, AA, AAA, and Major League Baseball) played between 2011 and 2017 was included. Each game was then classified as control game (games played in April, May, June, and September) or game within one month after the All-Star break. Incidence of injuries in games within one month of the All-Star break was compared with the control games.

Results

Our analysis included 66,642 games: 46,630 control games and 20,012 games played within one month after the All-Star break. On univariate analysis, there was a mean ± standard deviation of 0.45 ± 0.72 injuries per game in control games and 0.41 ± 0.68 injuries per game in games played within one month after the All-Star break (P<.001). On multivariate analysis, there was a significant association between games played within one month after the All-Star break and number of injuries per game (P<.001) after adjusting for the level of play and game duration. However, the effect size was 0.001, suggesting this effect is clinically insignificant.

Conclusion

There does not appear to be a clinically significant difference in injury rates per game in professional baseball players between games played in the month after the All-Star break and all other games played during the season. Although the All-Star break provides most players with a chance to rest, it does not appear to have an effect on injury rates.

Flexibility, Position, and Strength of the Shoulder Complex in Pediatric and Adult Amateur Tennis Athletes

CONTEXT

Understanding the musculoskeletal adaptations in the shoulder complex of varying ages of tennis athletes may suggest preventive protocols and conditioning and rehabilitation programs to this population. This study aimed to generate a bilateral descriptive profile of shoulder flexibility, scapular and clavicular position, and muscle strength in pediatric and adult amateur tennis athletes. The outcome measures were compared between groups and sides. The number and percentage of athletes "at risk" according to cutoff values for shoulder range of motion (ROM) were also analyzed.

DESIGN

Cross-sectional study.

METHODS

36 pediatric and 28 adult amateur tennis athletes were tested. Outcome measures were ROM of shoulder flexion, abduction, internal and external rotation, posterior capsule tightness, pectoralis minor index (PMI), scapular upward rotation, clavicular elevation, and strength of the external rotators, serratus anterior, and lower trapezius of the dominant/nondominant sides.

RESULTS

Pediatric athletes had greater dominant side external rotation (P = .01) and total ROM (P = .04), increased Low Flexion test (P = .01), and decreased PMI (P = .01) compared with the adults. Bilaterally, the pediatric athletes had greater dominant side external rotation ROM (P < .01) and decreased PMI (P = .002) as compared with their nondominant side, whereas the adults displayed lower values on posterior capsule tightness (P = .01) and decreased PMI (P = .02) on their dominant side compared with their nondominant side. For the remaining outcomes, no interaction effects were observed. The cutoff values for shoulder ROM showed that several athletes were "at risk" of shoulder problems.

CONCLUSION

Upper extremity adaptations at the shoulder are present in both pediatric and adult tennis athletes. These data can assist clinicians in better understanding the biomechanical adaptations in the shoulder of amateur tennis athletes in different age groups.

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.

Movement System Dysfunction Applied to Youth and Young Adult Throwing Athletes

Shoulder and elbow injuries in overhead athletes, especially baseball pitchers, have become more common and result in limited participation. Upper extremity injuries in baseball can occur secondary to high velocity repetitive loading at extreme ranges of motion causing microtrauma to the musculoskeletal structures. With the vast number of youth and young adult baseball players in the United States and the increasing number of throwing related injuries, it is crucial that clinicians can perform a movement system evaluation of the throwing motion. An adequate evaluation of the movement system as it relates to the throwing motion can provide insight into abnormal throwing mechanics and provide rationale for selecting appropriate interventions to address identified impairments that may lead to injury. The purpose of this clinical commentary is to present a recommended movement system evaluation that can be utilized during both pre-season and in-season to assess for modifiable injury risk factors in youth and young adult baseball players.

LEVEL OF EVIDENCE

5.

Scapular Dyskinesis in Elite Boxers with Neck Disability and Shoulder Malfunction

Background and Objectives: Neck and shoulder injuries commonly occur during boxing, and scapular dyskinesis is related to those injuries. This study investigated scapular dyskinesis with neck disability and shoulder malfunction in elite boxers. Materials and Methods: Seventy-two elite boxers participated in this study. Scapular dyskinesis was evaluated as normal, subtle, and obvious. Neck disability index (NDI), shoulder internal (IR), and external (ER) range of motion (ROM), isometric strength of IR and ER, and pectoralis minor length were measured and compared with the severity of scapular dyskinesis. Results: Thirty-eight boxers (52.7%) showed scapular dyskinesis. NDI score was significantly different (normal = 3.89 ± 3.08, obvious = 7.36 ± 4.95, p = 0.025). Isometric IR strength was significantly different (normal = 10.48 ± 2.86, obvious = 8.46 ± 1.74, p = 0.01). The length of the pectoralis minor was significantly different (normal = 10.17 ± 0.67, subtle = 9.87 ± 0.79, obvious = 9.47 ± 0.85; p = 0.001), and the dominant and non-dominant arm IR ROM was significantly different (dominant = 57.43 ± 11.98, non-dominant = 64.62 ± 10.3, p = 0.001). Conclusions: The prevalence of scapular dyskinesis is high among elite boxers. Boxers with scapular dyskinesis presented shoulder malfunction as well as neck disability. Further investigation is necessary to examine the relationship between scapular dyskinesis and neck disability in boxers.

Shoulder and Hip Range of Motion and Strength Changes Throughout a Season in College Softball Players

BACKGROUND

Many studies have been done on the strength and mobility of the shoulder and hip in baseball players, but fewer studies have examined these metrics in softball players.

PURPOSE

The purpose of this study was to observe and analyze changes in range of motion (ROM) and strength at the hip and shoulder that occur over the course of a competitive season, to describe preseason ROM and strength at the hip and shoulder in healthy college softball players through side-to-side comparison, and to compare measurements between pitchers and position players.

STUDY DESIGN

Descriptive Cohort Study.

METHODS

Data was collected over the course of six seasons, and a total of fifty-four healthy softball athletes (including pitchers and postiion players) who completed at least one set of preseason and postseason measurements were included. Subjects underwent passive ROM (External rotation [ER], internal rotation [IR], total arc of motion [TAM]) and strength (ER/IR at the shoulder, abduction/extension at the hip) measurements at preseason and postseason timepoints.

RESULTS

Over a season, position players demonstrated an increase in all ROM metrics in both shoulders, except dominant IR, and a decrease in ER strength at the shoulder bilaterally (p<0.05). They also showed decreased ROM in all metrics across both hips (p<0.05). Pitchers had increased IR and TAM ROM in the dominant shoulder, decreased strength in both shoulders (ER throwing; ER and IR non-throwing), decreased ROM in both hips, and decreased abduction strength in the non-dominant hip (p<0.05). Position players showed less preseason IR in the dominant shoulder compared to non-dominant IR (Dominant: 31.7 ± 1.6°, Non-dominant: 37.0 ± 2.3°; p<0.05).

CONCLUSION

Softball pitchers and position players both show increased ROM at the shoulder and decreased ROM at the hip over the course of a season. Position players demonstrated side-to-side discrepancies and seasonal changes at the throwing shoulder similar to those seen in baseball players. The preseason mobility of the dominant shoulder of pitchers increased over the season while strength of hip abduction in the non-dominant side was reduced.

LEVEL OF EVIDENCE

3.

The Relationship Between Functional Movement, Dynamic Stability, and Athletic Performance Assessments in Baseball and Softball Athletes

ABSTRACT

Stapleton, DT, Boergers, RJ, Rodriguez, J, Green, G, Johnson, K, Williams, P, Leelum, N, Jackson, L, and Vallorosi, J. The relationship between functional movement, dynamic stability, and athletic performance assessments in baseball and softball athletes. J Strength Cond Res 35(12S): S42-S50, 2021-Despite recent popularity, the relationship between movement quality and measures of athletic performance remains inconclusive. This investigation sought to clarify the relationships between measures of movement quality and measures of athletic performance in baseball and softball athletes. Thirty-eight National Collegiate Athletic Association Division I baseball (n = 23; age 20.00 ± 1.38 years, lower-extremity [LE] limb length 93.91 ± 4.37, upper-extremity [UE] limb length 92.37 ± 4.48) and softball (n = 15; age 19.93 ± 1.28 years, LE limb length 89.43 ± 4.67, UE limb length 84.61 ± 4.39) athletes completed the Functional Movement Screen (FMS) and the Y Balance Test for the lower and upper extremities (YBTLQ and YBTUQ, respectively). Performance assessments were proagility (PA), vertical jump (VJ), and rotational medicine ball throw to the right and left (RMTR and RMTL, respectively). No significant correlations were seen between any of the composite scores of movement quality and athletic performance in baseball athletes; shoulder mobility was weakly correlated with PA (rs = 0.442, p = 0.035). Composite FMS was negatively correlated with RMTR (rs = -0.753) in softball athletes. In addition, in softball athletes, RMTR was negatively correlated with in-line lunge (rs = -0.544, p = 0.04), trunk stability push-up (rs = -0.761, p = 0.002), anterior YBTLQ reach (r = -0.628), and posterolateral YBTLQ reach (r = -0.683); VJ was correlated with posterolateral YBTLQ reach (r = 0.531) and superolateral (SL) YBTUQ reach (r = 0.591), and PA was negatively correlated with posterolateral YBTLQ (r = -0.60) and SL YBTUQ reach (r = -0.557). The differences in correlations of movement quality and athletic performance between baseball and softball athletes suggest movement quality influences performance differently in female athletes and male athletes.

Development and internal validation of a humeral torsion prediction model in professional baseball pitchers

BACKGROUND

Humeral torsion (HT) has been linked to pitching arm injury risk after controlling for shoulder range of motion. Currently measuring HT uses expensive equipment, which inhibits clinical assessment. Developing an HT predictive model can aid clinical baseball arm injury risk examination. Therefore, the purpose of this study was to develop and internally validate an HT prediction model using standard clinical tests and measures in professional baseball pitchers.

METHODS

An 11-year (2009-2019) prospective professional baseball cohort was used for this study. Participants were included if they were able to participate in all practices and competitions and were under a Minor League Baseball contract. Preseason shoulder range of motion (external rotation [ER], internal rotation [IR], horizontal adduction [HA]) and HT were collected each season. Player age, arm dominance, arm injury history, and continent of origin were also collected. Examiners were blinded to arm dominance. An a priori power analysis determined that 244 players were needed for accurate prediction models. Missing data was low (<3%); thus, a complete case analysis was performed. Model development followed the transparent reporting of a multivariable prediction model for individual prognosis or diagnosis (TRIPOD) recommendations. Regression models with restricted cubic splines were performed. Following primary model development, bootstrapping with 2000 iterations were performed to reduce overfitting and assess optimism shrinkage. Prediction model performance was assessed through root mean square error (RMSE), R², and calibration slope with 95% confidence intervals (CIs). Sensitivity analyses included dominant and nondominant HT.

RESULTS

A total of 407 professional pitchers (age: 23.2 [standard deviation 2.4] years, left-handed: 17%; arm history prevalence: 21%) participated. Predictors with the highest influence within the model include IR (0.4, 95% CI 0.3, 0.5; P < .001), ER (-0.3, 95% CI -0.4, -0.2; P < .001), HA (0.3, 95% CI 0.2, 0.4; P < .001), and arm dominance (right-handed: -1.9, 95% CI -3.6, -0.1; P = .034). Final model RMSE was 12, R² was 0.41, and calibration was 1.00 (95% CI 0.94, 1.06). Sensitivity analyses demonstrated similar model performance.

CONCLUSIONS

Every 3° of IR explained 1° of HT. Every 3° of ER explained 1° less of HT, and every 7° of HA explained 1° of HT. Right-handers had 2° less HT. Models demonstrated good predictive performance. This predictive model can be used by clinicians to infer HT using standard clinical test and measures. These data can be used to enhance professional baseball arm injury examination.