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Background: Excessive shoulder anterior force has been implicated in pathology of the rotator cuff in little league and professional baseball pitchers; in particular, anterior laxity, posterior stiffness, and glenohumeral joint impingement. Distinctly characterized motions associated with excessive shoulder anterior force remain poorly understood. Methods: High school and professional pitchers were instructed to throw fastballs while being evaluated with 3D motion capture (480 Hz). A supplementary random forest model was designed and implemented to identify the most important features for regressing to shoulder anterior force, with subsequent standardized regression coefficients to quantify directionality. Results: 130 high school pitchers (16.3 ± 1.2 yrs; 179.9 ± 7.7 cm; 74.5 ± 12.0 kg) and 322 professionals (21.9 ± 2.1 yrs; 189.7 ± 5.7 cm; 94.8 ± 9.5 kg) were included. Random forest models determined nearly all the variance for professional pitchers (R2 = 0.96), and less than half for high school pitchers (R2 = 0.41). Important predictors of shoulder anterior force in high school pitchers included: trunk flexion at maximum shoulder external rotation (MER) (X.IncMSE = 2.4, β = −0.23, p < 0.001), shoulder external rotation at ball release (BR)(X.IncMSE = 1.7, β = −0.34, p < 0.001), and shoulder abduction at BR (X.IncMSE = 3.1, β = 0.17, p < 0.001). In professional pitchers, shoulder horizontal adduction at foot contact (FC) was the highest predictor (X.IncMSE = 13.9, β = 0.50, p < 0.001), followed by shoulder external rotation at FC (X.IncMSE = 3.6, β = 0.26, p < 0.001), and maximum elbow extension velocity (X.IncMSE = 8.5, β = 0.19, p < 0.001). Conclusion: A random forest model successfully selected a subset of features that accounted for the majority of variance in shoulder anterior force for professional pitchers; however, less than half of the variance was accounted for in high school pitchers. Temporal and kinematic movements at the shoulder were prominent predictors of shoulder anterior force for both groups. Clinical relevance: : Our statistical model successfully identified a combination of features with the ability to adequately explain the majority of variance in anterior shoulder force among high school and professional pitchers. To minimize shoulder anterior force, high school pitchers should emphasize decreased shoulder abduction at BR, while professionals can decrease shoulder horizontal adduction at FC. [ABSTRACT FROM AUTHOR]

Background: Elbow flexion at late portions of the pitch has been associated with increased elbow varus torque, a kinetic surrogate associated with injury risk. Direct examinations of injury incidence with elbow flexion angles have not been conducted in professional pitchers. Purpose: To compare elbow and shoulder injury incidence among professional baseball players stratified by degree of elbow flexion at ball release (BR). Study Design: Descriptive laboratory study. Methods: Professional pitchers (N = 314) were instructed to pitch between 8 and 12 fastballs while being evaluated using motion capture technology. Upper extremity injury incidence was recorded upon interview. Pitchers were subsequently subdivided into 3 groups based on increasing elbow flexion at BR. Analysis of variance was used to compare participant characteristics and kinematic and peak kinetic variables. An odds ratio (OR) was calculated to determine the risk of having a previous upper extremity injury based on the degree of elbow flexion at BR. Results: A total of 116 pitchers (132 documented injuries) had a previous upper extremity injury, with elbow injury (76 injuries; 57.6%) being the most common. Evaluation of kinetic values showed that pitchers with the smallest elbow flexion at BR had significantly less peak elbow flexion torque than did those with greatest elbow flexion at BR (3.8 ± 0.5 vs 4.1 ± 0.6 %weight × height; P =.003). Pitchers who demonstrated a greater than average degree of elbow flexion at BR when pitching were more likely to have a history of elbow injury (OR, 1.97; 95% CI, 1.14-3.40; P =.015) and olecranon spur formation or stress fracture (OR, 5.79; 95% CI, 1.25-26.85; P =.025). Conclusion: Pitchers with greater elbow flexion at BR had significantly higher odds of previous injury of the elbow and olecranon. Increasing elbow flexion has been shown to place the medial elbow in a position to carry a greater amount of load, which may be exacerbated during the final moments of the pitching motion. Professional pitchers can consider decreasing elbow flexion at BR as a potential, modifiable risk factor for elbow injury, in particular for olecranon spur formation and fracture. Clinical Relevance: This study attempts to associate injury incidence with a modifiable, kinematic variable for an at-risk population. [ABSTRACT FROM AUTHOR]

Background Core injuries in professional baseball pitchers have been linked to both diminished performance and time missed during the season injury was sustained. It is currently unclear how a history of a core injury may affect the future pitching performance and mechanics of professional baseball pitchers. Purpose To compare kinetic and kinematic variables between professional baseball pitchers with prior core/groin injuries and those without prior injury. Study design Descriptive laboratory study. Methods Professional baseball pitchers with a history of core injury pitched 8--12 fastball pitches while evaluated with 3D-motion capture (480 Hz). Inclusion criteria necessitated that the core injury occurred within one to four-years prior to biomechanical evaluation and that the core injury required time off from professional play for a minimum of 2 weeks and maximum of 3 months. These pitchers were 4:1 propensity-scored matched by age, height, weight, and handedness to pitchers with no prior injury history (control). Twenty kinematic and eleven normalized and non-normalized kinetic parameters were compared between groups using appropriate parametric testing. Sub-analysis of pitchers with distinct core muscle and spinal injuries were also analyzed. Results The No Prior Injury (NPI) subgroup (n = 76) had significantly less elbow flexion at ball release (31 ± 5° vs. 35 ± 6° respectfully, p = 0.044) compared to the Core Musculature/Soft Tissue subgroup (CM/ST, n = 10), with no significant difference in kinematics for other injury groups (p > 0.05). The General Core/Groin injury group (GCG, n = 19) had significantly greater normalized elbow anterior force (43.9 ± 4.7 vs. 40.0 ± 5.2 %BodyWeight[BW], p = 0.006) and elbow flexion torque (4.3 ± 0.5 vs. 3.8 ± 0.5 %BWxBodyHeight[BH], p = 0.001) than the NPI pitchers. CM/ST had significantly greater normalized elbow anterior force (p = 0.031), elbow flexion torque (p = 0.002), and shoulder adduction torque (p = 0.007) than NPI pitchers. Conclusion Professional baseball pitchers with prior core/groin injuries demonstrated increased elbow anterior force and elbow flexion torque compared to pitchers with no prior core injuries. One possible explanation for this finding includes inadequate recruitment and utilization of the lower extremities as a component of the kinetic chain leading to compensation at the level of the throwing arm. Whether these kinetic differences arise as a consequence of injury or present a risk for such warrants additional investigation. [ABSTRACT FROM AUTHOR]