Search Results (21)

Background: Anterior cruciate ligament (ACL) injuries are increasing in young athletes and many are related to non-contact, spontaneous mechanical fatigue-related ruptures. The objective of this narrative review is to identify and synthesize the anatomical, histological, physiological, and biomechanical basis of extracellular matrix (ECM) factors that contribute to ACL injuries and suggest ways to decrease their occurrence. Methods: The primary investigator searched PubMed, Web of Science, and Google Scholar database titles and abstracts using search phrases with Boolean operators: “anterior cruciate ligament” OR “ACL”, OR “cranial cruciate ligament” AND “disease”; “anterior cruciate ligament” OR “ACL”, OR “cranial cruciate ligament” AND “spontaneous rupture” OR “non-contact injury”; and “anterior cruciate ligament” OR ACL, OR cranial cruciate ligament” AND “crosslink”, “collagen” OR “extracellular matrix”; and “anterior cruciate ligament” OR “ACL”, OR “cranial cruciate ligament” AND “microtrauma”, OR “sudden” OR “fatigue failure”. The primary investigator and a sports orthopedic surgeon reviewed titles and abstracts of diverse evidence sources. From these identified sources, the study team performed full text reviews, selected contributing articles, performed Strength of Recommendation Taxonomy (SORT) grading, and synthesized the following themes: A Hostile Environment, ACL Strain, and Poor Nutrient Delivery; Accumulative ACL Microtrauma and Mechanical Failure; The ACL Differs From Other Ligaments; Collagen, the ECM, and ACL Mechanobiology; Crimps and ACL ECM Stretch; Crosslinks Improve ECM Mechanical Properties; The Delicate Collagen Synthesis and Degradation Balance; Exercise Training and the ACL; Can Nutraceuticals Help Restore the Balance?; Training Induced ACL Hypoxia; Estrogen and the Female Athlete; Counting Pitches or Counting Collagen Fiber Ruptures; and Restoring A Positive Anabolic–Catabolic Collagen Balance. Results: Regular exercise training within a physiologically safe loading range is vital to ACL ECM health. However, low or moderate evidence suggested that poor blood supply, slow metabolism, and a hypoxic environment may unbalance anabolic and catabolic homeostasis. Active rest and recovery concepts that prevent youth baseball shoulder and elbow injuries may help prevent non-contact ACL injuries. Conclusions: More prescriptive active rest and recovery intervals and neuromuscular control training may restore the anabolic–catabolic balance that increases mature crosslink density and improves ACL ECM strength. Confirmatory studies are needed to better establish therapeutic intervention mode(s), timing, dosage, and frequency optimization. Full article

Background/Objectives: This study investigated biomechanical differences between right-handed (RHPs) and left-handed (LHPs) youth baseball players by analyzing shoulder and elbow range of motion (ROM), muscle strength, and humeral torsion. Side-to-side asymmetries were also examined to identify potential handedness-related adaptations. Methods: This cross-sectional study included 2008 youth baseball players (1829 RHPs and 179 LHPs) aged 9–13 years; female players were excluded because of their small number, and only male participants were analyzed. Shoulder and elbow ROM, muscle strength, and humeral torsion were evaluated, with humeral torsion data collected from 1024 measurements (946 RHPs, 78 LHPs). Group differences were analyzed using the Mann–Whitney U and Wilcoxon Signed-Rank tests. Logistic regression analysis identified independent factors associated with being an LHP, while Pearson correlation analyses explored the relationships between humeral torsion and external/internal rotation. Results: LHPs exhibited significantly larger nondominant shoulder external rotation (p < 0.001), dominant internal rotation (p = 0.003), dominant shoulder horizontal adduction (p = 0.007), dominant elbow flexion (p = 0.006), and side-to-side prone internal rotation strength ratio (p < 0.001). LHPs also showed smaller dominant shoulder external rotation (p = 0.012), nondominant shoulder internal rotation (p = 0.001), nondominant horizontal adduction (p = 0.037), dominant prone external rotation strength (p = 0.002), and humeral torsion (p = 0.031). Humeral torsion differences correlated with external rotation in LHPs (r = 0.236) and internal rotation in RHPs (r = −0.153). Predictors of left-handedness included lower dominant shoulder external rotation (OR = 0.937) and higher dominant elbow flexion (OR = 1.410). Conclusions: This study provides novel insights into the normal functional characteristics of LHPs, an area that has been relatively underexplored. These findings serve as a basis for future studies on risk assessment, injury prevention, and performance optimization in youth baseball players. Full article

Pelvis and trunk counter-rotation are key factors known to effect throwing arm kinematics in baseball pitching, where energy or momentum is transferred from the lower extremities through to the trunk during the pitching cycle. The purpose of this study was to retrospectively analyze previously recorded motion capture data of 19 skilled competitive pitchers to test the a priori hypothesis whether different stride lengths affect transverse pelvis and trunk biomechanics. A blinded randomized crossover design was used where pitchers threw two simulated games at ±25% from desired stride length (DSL), respective of overstride (OS) and under-stride (US). Variables of interest included pelvic–trunk separation (PTS) angle or degree of uncoupling and proximal plyometric effect (PPE) or ratio between trunk–pelvis angular velocities, as surrogate measures of rotational and elastic energy transfer. Paired t-tests were used to compare across stride conditions. A one-way ANOVA with a Bonferroni post hoc analysis demonstrated stride lengths differed statistically, (DSL vs. OS p = 0.006), (DSL vs. US, p < 0.001), and (US vs. OS, p < 0.001). Despite the statistically different stride lengths, fastball velocities tracked with radar were consistent. No significant differences within and across innings pitched between OS and OS conditions were found. The ±25% stride length changes influenced temporal parameters within the pitching cycle. Shorter stride elicited by early SFC reduced time during the Generation phase and extended the Brace-Transfer duration (p < 0.001). Statistically different transverse pelvis and trunk kinematics at hallmark events and phases consequently influenced pelvic–trunk separation and proximal plyometrics. During the Generation (PKH-SFC) and Brace-Transfer (SFC-MER) phases, the pelvis and trunk were significantly more externally rotated (p < 0.001) with shorter strides, concomitant with less separation at the instant of SFC and the Generation phase with greater peak proximal plyometrics effect ratios peak during throwing arm acceleration, indicative of greater contribution of trunk angular velocity (p < 0.05). Greater transverse trunk angular velocities relative to the pelvis late in double support necessitates the throwing arm to “catch up” from a position of greater arm lag, which compromises the dynamic and passive stabilizers. In conclusion, stride length alters pitching biomechanics and timing of peak pelvic–trunk separation and trunk angular velocity relative to the pelvis. Increased shoulder and elbow tensile stress is to be expected, consequently increasing risk for injury. Full article

Background/Objectives: Baseball pitchers accumulate extreme upper extremity forces during the repetitive, high-velocity motion of throwing, which can lead to shoulder dysfunction and overuse injuries. Although scapular dyskinesis has been linked to various shoulder pathologies, there is a lack of evidence on the specific scapular patterns predisposing pitchers to injury. Methods: A total of 85 professional pitchers from a single professional baseball organization participated in the entirety of this study. All subjects had their scapular positions and motion patterns measured via a digital goniometer prior to the beginning of a competitive season. Scapular upward/downward rotation, anterior/posterior tilt, and internal/external rotation were assessed with the shoulder at rest and during elevation to 120° in the scapular plane. Overuse injuries of the shoulder/elbow sustained during the subsequent competitive season were documented by the team’s medical staff, with statistical comparisons between the injured (n = 34) and non-injured (n = 51) group for each scapular measure. Results: Pitchers who sustained shoulder/elbow injuries demonstrated significantly more scapular anterior tilt during humeral elevation compared to those without an injury (p = 0.04). The difference in anterior tilt between the two groups was 3.8° and had a medium effect size, suggesting clinical relevance. No significant between-group differences were found in any other scapular positions or motions (p > 0.22). Conclusions: Pitchers with increased scapular anterior tilt were more likely to sustain a shoulder/elbow injury, highlighting this kinematic feature as a potential risk factor. This finding suggests that anterior tilt might contribute to soft tissue strain, increasing injury susceptibility in pitchers. Full article

Ulnar collateral ligament (UCL) injuries are a major concern in baseball because of repetitive valgus stress from overhead throwing, often leading to surgical intervention. In recent years, UCL reconstruction has become increasingly frequent. Although this procedure has a high success rate, revision surgery is often required. This systematic review and meta-analysis examined the incidence of UCL surgery and revision procedures in baseball players, explored potential risk factors, and identified areas for future research. A comprehensive search of PubMed, Google Scholar, CINAHL, Embase, and SportDiscus databases was conducted for studies published between 2014 and 2024. Studies reporting the incidence of primary and revision UCL reconstructions in baseball players were included. The quality of the included studies was assessed using the Methodological Index for Non-randomized Studies (MINORS). A meta-analysis using RevMan 5.4 software calculated the pooled proportions and 95% confidence intervals for UCL surgery and revision rates. Six studies met the inclusion criteria, including data from 27,366 baseball players. The pooled incidence of UCL surgery was 4.52% (95% CI: 4.20–4.84%), and the pooled incidence of revision surgery was 8.42% (95% CI: 5.49–11.35%). Statistical analyses showed high heterogeneity (I² = 100%, p < 0.00001). Sensitivity analyses were performed to assess the robustness of the results, both in the incidence of surgery and in the revision surgery. UCL surgery is a common procedure in baseball, and a notable proportion of athletes require revision. Further research is necessary to identify the risk factors and develop preventive strategies to reduce UCL injury rates. Full article

Background/Objectives: In overhead throwing sports such as baseball and softball, upper extremity injuries are prevalent at both collegiate and high school levels. Currently, there is no universal assessment protocol to identify athletes at risk for injury or to determine their readiness to return to sport. This study aimed to investigate the relationship between shoulder internal rotation (IR) and external rotation (ER) isometric strength in a throwing position and three upper extremity functional tests among collegiate baseball players. It was hypothesized that there would not be significant correlations between shoulder IR and ER peak isometric force and the following functional assessments: the Upper Quarter Y Balance Test (YBT-UQ), seated single-arm shot put, and Closed Kinematic Chain Upper Extremity Strength Test (CKCUEST). Methods: Forty healthy collegiate baseball players volunteered for the study. After completing a self-guided warm-up, participants performed bilateral isometric shoulder IR and ER strength tests at 90 degrees of shoulder abduction and elbow flexion, followed by the three functional tests in random order. Relationships were analyzed using Pearson’s correlation coefficients (r), with a significance level set at p < 0.05. Results: Correlations were generally low, ranging from r = 0.001 to r = 0.551. Significant correlations were observed between the CKCUEST and dominant IR strength (r = 0.345, p = 0.031), dominant ER strength (r = 0.407, p = 0.010), and non-dominant ER strength (r = 0.551, p < 0.001). Additionally, a significant correlation was found between the dominant ER/IR strength ratio and the dominant arm superolateral reach on the YBT-UQ (r = −0.352, p = 0.026). No significant correlations were identified between isometric shoulder strength and the single-arm shot put. Conclusions: Most correlations were low to moderate, and only significant correlations between shoulder rotation isometric strength and one direction of the YBT-UQ and the CKCUEST were observed. Thus, shoulder rotation strength in a position similar to the cocking phase of overhead throwing may be valuable for return-to-sport criteria and injury screening for overhead athletes. However, further research is needed to validate these findings. Full article

Shoulder and elbow injuries are prevalent among baseball players, particularly pitchers, who experience repetitive eccentric loading of the shoulder, leading to muscle damage and increased injury risk. Nearly 40% of shoulder injuries in baseball occur in pitchers, with many facing low rates of return to sport. The rotator cuff (RC) muscles—supraspinatus (SSP), infraspinatus (ISP), subscapularis (SSC), and teres minor (TMin)—are crucial for shoulder stability, movement, and force generation, particularly in overhead sports. Each RC muscle comprises subregions with distinct biomechanical properties, such as strength, moment arm behavior, and activation patterns. These differences allow for a finely tuned balance between joint stability and mobility. For example, the superior subregion of the ISP significantly contributes to external rotation, a function critical in sports like baseball that require precision and power. During pitching, the SSP, ISP, and SSC stabilize the glenohumeral joint through high activation during explosive phases, such as stride, arm cocking, and arm acceleration. Understanding these functional subregional differences is vital for diagnosing and managing shoulder pathologies like RC tears. Despite advancements, clinicians face challenges in predicting re-injury risks and determining return-to-play readiness for athletes with shoulder injuries. Integrating insights into subregional biomechanics with patient care could enhance outcomes. Tailored interventions—whether surgical or rehabilitative—targeting specific subregions could improve recovery times, reduce re-injury risks, and enable more personalized treatment plans. Such approaches are especially beneficial for athletes, older individuals, and those prone to RC injuries, promoting better long-term shoulder health and performance. The present work aims to highlight some of the research on these subregions and their differences, providing insights to enhance treatment approaches for shoulder injuries. Full article

This study aimed to examine prospectively the relationship between the deep squatting test and medial elbow injuries in elementary school baseball players and to determine the usefulness of the lower extremity field test in throwing injuries. The participants were 254 players who had participated in preseason medical checkups in both 2019 and 2020 and had no problems with the 2019 medical checkups. The evaluation parameters included ultrasonography examination, physical examination, and three types of deep squatting tests. The success rate of deep squatting tests was significantly lower in the injured group than in the non-injured group in the medial elbow injuries. By the difficulty level, the backward test in the deep squatting test was more likely to predict medial elbow injuries than the forward and middle tests. Furthermore, there was a significant difference in the squatting test and medial elbow injuries by grades. In conclusion, this is the first prospective study to provide evidence that the deep squatting tests, classified by difficulty level, can predict the risk of subsequent medial elbow injuries in elementary school players. The deep squatting test may be useful as a field test for lower extremity flexibility that can be performed by athletes and instructors, as it can predict the risk of subsequent medial elbow injuries. Full article

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

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

On-field screening for ‘elbow injury in baseball’, a condition commonly seen in youth baseball players, was conducted over two years on 160 elementary school students in Ibaraki Prefecture, Japan. This on-field screening was conducted in collaboration with the Ibaraki Prefecture High School Baseball Federation. Pitchers, catchers, symptomatic players, and players who had previously experienced elbow pain were given a comprehensive evaluation that included a physical exam and ultrasound. Out of the 135 students who were successfully screened, 10 were diagnosed with osteochondritis dissecans of the humeral capitellum (OCD). Notably, seven among these were asymptomatic. This assessment identified limited range of motion and pain when extending their elbow as significant risk factors for OCD. An attempt at on-field screening for baseball elbow injuries in collaboration with the local baseball federation was introduced. The risk factors for OCD were identified. Considering these factors, more efficient screening will be possible in the next attempt. Full article

There are no reports investigating the relationship between shoulder range of motion (ROM) and pitching elbow torque in junior high school pitchers. Therefore, we aimed to evaluate the factors associated with medial elbow torque in this population. Sixty-three junior high school baseball pitchers were recruited for this study. The participants completed a questionnaire and passive ROM measurements of shoulder abduction and horizontal adduction. All pitchers pitched three fastballs at maximum effort while wearing a wireless sensor recording pitching mechanics and elbow valgus torque for each pitch. Age (r = 0.65, p < 0.001), height (r = 0.83, p < 0.001), body weight (r = 0.82, p < 0.001), BMI (r = 0.60, p < 0.001), and ball velocity (r = 0.80, p < 0.001) were significantly positively correlated with elbow valgus torque. Participants were divided into two groups based on elbow valgus torque, >30 (high torque [HT]) and <30 N·m (low torque [LT]). Age, height, body weight, BMI, and ball velocity were significantly higher in the HT group than in the LT group. The difference between dominant and non-dominant shoulder horizontal adduction ROM was 5.3 ± 9.3° and 1.0 ± 6.4° in the HT and LT groups, respectively, which was also significantly different. Ball velocity, age, larger physique, and increased restriction of the dominant shoulder’s horizontal adduction ROM were associated with higher medial elbow torque in junior high school pitchers. This suggests that improving the dominant shoulder’s horizontal adduction ROM contributes to preventing elbow injuries. Full article

This study aimed to describe the injury profiles of young Korean baseball players according to position and age as the proportion and distribution of injuries based on playing position and age remains unclear. A total of 271 elite youth baseball players aged 8 to 16 years were divided into two groups: elementary school (ES) (n = 135) and middle school (MS) (n = 136). The participants’ basic, baseball practice, and injury information were collected. Injuries in the MS group were not limited to the elbow and shoulder, and injury prevalence varied by age group and baseball position. The most injured body region in the ES group was the elbow joint, regardless of the position. In contrast, the most injured body region in the MS group was the lower back, except for infielders whose elbows were the most injured. Additionally, the MS group was more likely to experience injuries to the lower back (OR = 4.27, 95% CI = 2.47–7.40), shoulder (OR = 1.93, 95% CI = 1.08–3.43; p = 0.024), and knee (OR = 2.15, 95% CI = 1.17–3.94; p = 0.012). Our findings indicate that excessive practice and a lack of rest during MS (growth spurt period) can significantly increase the risk of lower back problems in young baseball players. Full article

Altered propulsive and bracing ground reaction forces from lower-body fatigue significantly impact stride length to increase weakness in dynamic elbow stabilizers and risk of medial elbow injury in baseball pitchers. This work investigated altered stride length on three-dimensional ankle joint dynamics to illustrate fatigue-induced changes in ankle motion that can also be impacted by coaching errors. Nineteen pitchers (15 collegiate and 4 high school) were randomized in a crossover design study that encouraged fatigue by throwing two simulated 80-pitch games at ±25% of their desired stride length. An integrated motion-capture system with two force plates and radar gun tracked each throw. Retrospective analysis using pairwise comparisons, including effect size calculations, were undertaken to identify differences in ankle dynamics between stride length conditions for both the drive and stride leg. Longer strides were found to be more effective in drive ankle propulsion and stride-bracing mechanics. Conversely, shorter strides delayed bracing dynamics by demonstrating continued drive ankle plantar flexion moments after stride-foot contact to extend pitchers’ time in propulsion (p < 0.001, d > 0.8). Additionally, heightened braking effects were seen during the acceleration phase of throwing with greater stride knee extension power when pitching with shorter strides (p < 0.001, d > 0.8). The knowledge gained from this work offers new insight into compensatory stride length adaptation that impacts systemic and throwing arm-specific fatigue to maintain ball velocity, as bilateral ankle joint dynamics can be significantly affected in response to cumulative workload. Full article

The pronator teres muscle is a major dynamic stabilizer of elbow valgus stress during throwing. This study aims to investigate pronator teres muscle activation during breaking ball pitching in baseball pitchers. Twelve male college baseball players with more than eight years of baseball experience were included in this study. A wireless surface electromyography (EMG) system was used to measure the activation of the forearm muscles and record EMG data during fastball and curveball pitching. Peak pronator teres muscle activation during curveball pitching was greater than that during fastball pitching (p = 0.03). There was no difference in the muscle activation of the other forearm muscles (p > 0.05). These results indicate that increased muscle activity in the pronator teres may contribute to stiffness and induce pronator teres syndrome or medial elbow injuries related to the overuse of the pronator teres, especially during curveball pitching. Controlling curveball throws contributes to player coaching and conditioning for the prevention of elbow joint disorders and pronator teres syndrome. Full article