Maximum Shoulder External Rotation Research Articles

Limited Total Arc Glenohumeral Rotation and Shoulder Biomechanics During Baseball Pitching.

Upper extremity injuries in baseball pitchers cause significant time loss from competing and decreased quality of life. Although shoulder range of motion (ROM) is reported as a key factor to prevent potential injury, it remains unclear how limited glenohumeral ROM affects pitching biomechanics which may contribute to upper extremity injuries. To investigate how pitchers with decreased total arc glenohumeral ROM of the throwing arm differed in upper extremity pitching kinematics and kinetics as well as ball velocity compared with pitchers with greater levels of glenohumeral ROM. Cross-sectional study. Laboratory. Fifty-seven baseball pitchers (ages 18-24) were divided into either control (≥160° total arc) or lower ROM (<160° total arc) groups. The mean glenohumeral ROM deficits, pitching kinematic and kinetic outcomes, and ball velocity were compared between groups. The control group demonstrated significantly less deficit in total arc ROM between arms than the lower ROM (control: -1.5° ± 10.0°; lower ROM: -12.4° ± 13.9°; P < .001). While the lower ROM group displayed less maximal shoulder external rotation (ER) while pitching, the control group had significantly less difference in ROM between maximal shoulder ER while pitching and clinically measured ER (lower ROM: 64.4° ± 12.1°; control: 55.8° ± 16.6°; P = .025). The control group had significantly faster ball velocity than the lower ROM group (control: 85.0 ± 4.3 mph; lower ROM: 82.4 ± 4.8 mph; P = .024). Pitchers with decreased total arc glenohumeral ROM (<160° total arc) may undergo overstretching toward ER in the shoulder during the late cocking phase. Pitchers with higher total arc ROM can pitch the same or faster ball without increasing loading in the upper extremity. Total arc glenohumeral ROM measurement can be a clinical screening tool to monitor shoulder condition over the time, and pitchers with limited total arc ROM might be at higher risk of shoulder injury.

Professional baseball pitchers produce similar ball velocity and kinematics when pitching from the wind-up and stretch deliveries: a biomechanical analysis

ABSTRACT Historically, the wind-up delivery is considered a more biomechanically advantageous pitching motion compared to the stretch. Recently, some pitchers have shifted to pitching exclusively from the stretch regardless of the game situation. The goal of this study was to compare temporal, kinematic and kinetic variables between the wind-up and stretch deliveries. Professional pitchers (n = 52, 189.1 ± 4.8 cm, 92.8 ± 8.4 kg) threw fastballs evaluated by 3D-motion capture (480 Hz) from both the wind-up and stretch deliveries. Within a pitcher, there was no significant difference in ball velocity between the two deliveries (p = 0.15). The stretch delivery was significantly quicker to ball release at toe off 2 (p < 0.001) (the last frame the pitcher’s foot contacts the ground before progressing to maximum knee height) and maximum knee height (p < 0.001). The majority of differences occurred prior to foot contact. The wind-up delivery produced greater maximum shoulder external rotation (p < 0.001) and lead knee flexion at ball release (p < 0.001). Pitching from the stretch incurred greater shoulder superior force (p < 0.001). It remains unknown if this is clinically significant as pooled means show only a 2% difference. Therefore, pitching a fastball from either the wind-up or stretch delivery provides comparable mechanics and throwing arm load with likely comparable risk of injury.

Literature review of specific techniques in catching and throwing in infield defense in baseball - retrospective article

&lt;p&gt;目的：內野手可以是整個棒球守備的核心，棒球守備各階段全身上下的協調，有許多值得探討的專項技巧。方法：本研究使用Google scholar，以Baseball infielder、內野、野球守備、內野捕球、守備ゴロ等關鍵字，搜尋台灣、日本、美國三國關於棒球內野守備專項技巧的文獻做歸納，以不同角度探討內野守備的專項技巧：一、內野守備接球，二、內野守備傳球，三、守備的分期與各分期之動作控制。結果：本篇回顧性論文發現，一、移動腳步到好接球的彈跳點是良好守備的關鍵。二、減少軸心腳在接球位置上的變化和較為前面的接球點，對於接球的穩定性至關重要，甚至會影響到後續傳球的動能。三、精簡接傳的動作相較於增加傳球球速可能可以更能有效減少整體守備時間。四、優秀選手在接球的過程中會儘早讓軸心腳著地，並前期和中期將重心保留在軸心腳。五、內野手傳球在前導腳接觸時，軀幹向後扭轉和肘部伸展角度都會比投手小。結論：無論是接球前腳步移動的節奏和精確性，還是接球時的接球點和接短彈跳的能力，甚至是軀幹和骨盆前傾的時機點，對於內野守備過程都產生一定的影響。建議在日常練習時，就能將接短彈跳、腳步移動，納入訓練課表中，並且在動作過程中，加以檢視軀幹的姿勢，方能在比賽時擁有良好的守備表現。&lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;&lt;p&gt;The standing throw with run-up is the best approach to evaluate the performance of energy transfer and the efficiency of throwing motions for handball players. Purpose: This research aims at analyzing the usage of the standing throw with run-up among the handball players in Taiwan. The roles of body kinematics, strength of core muscles and standing balance of the drive leg played in the standing throw with run-up are also discussed. Methods: Nine Division I handball players from college went through a series of tests. The motions and the speed of the handball throwing were detected by a 3D electromagnetic motion analysis system and a sports radar gun, respectively. The maximum isometric muscle strength of trunks and hips were measured by a torque sensor and a home-made device of strength measurement. The standing balance of the drive leg was measured by a force plate with a mat. Results: The maximal shoulder external rotation angle in the arm cocking phase, the maximal trunk rotation velocity in the arm acceleration phase and the maximal shoulder horizontal adduction velocity showed moderate positive relationships with the ball velocity. The strength of back muscles had a moderate negative relationship with the ball velocity. The correlation between the balance ability of the drive leg and the ball velocity was not observed. Conclusion: The importance of proximal segments to the standing throw with run-up is analyzed by kinematical analysis. It is suggested that the energy of handball throwing is generated by the upper extremities or other limb segments in the processes of the standing throw with run-up. Our findings can serve as a helpful reference for both coaches and players.&lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;

Kinematic Modeling of Pitch Velocity in High School and Professional Baseball Pitchers: Comparisons With the Literature.

Kinematic parameters predictive of pitch velocity have been evaluated in adolescent and collegiate baseball pitchers; however, they have not been established for high school or professional pitchers. To create multiregression models using anthropometric and kinematics features most predictive for pitch velocity in high school and professional pitchers and compare them with prior multiregression models evaluating other playing levels. Descriptive laboratory study. High school (n = 59) and professional (n = 337) baseball pitchers threw 8 to 12 fastballs while being evaluated with 3-dimensional motion capture (480 Hz). Using anthropometric and kinematic variables, multiregression models for pitch velocity were created for each group. A systematic review was conducted to determine previous studies that established kinematic models for ball velocity in youth, high school, and collegiate pitchers. Leg length was predictive of pitch velocity for high school and professional pitchers (P < .001 for both). When compared with previously established models for pitch velocity, almost all groups were distinct from one another when assessing age (P maximum < .001), weight (P max = .0095), and pitch velocity (P max < .001). Stride length was a significant predictor for the youth/high school pitchers, as well as the current study's high school and professional pitchers (P < .001 for all). Maximal shoulder external rotation (collegiate: P = .001; professional: P < .001) and maximal elbow extension velocity (high school/collegiate: P = .024; collegiate: P < .001; professional: P = .006) were shared predictors for the collegiate and current study's professional group multiregression models. Trunk flexion at ball release was a commonly shared predictor in the youth/high school (P = .04), high school/collegiate (P = .003), collegiate (P < .001), and the current study's professional group (P < .001). Youth, high school, collegiate, and professional pitchers had unique, predictive kinematic and anthropometric features predictive of pitch velocity. Leg length, stride length, trunk flexion at ball release, and maximal shoulder external rotation were predictive features that were shared between playing levels. Coaches, clinicians, scouts, and pitchers can consider both the unique and the shared predictive features at each playing level when attempting to maximize pitch velocity.

Relationship between glenohumeral horizontal abduction angle and scapular internal rotation angle at maximum shoulder external rotation during baseball pitching

BackgroundIncreased scapulothoracic (ST) internal rotation at maximum external rotation (MER) during baseball pitching can decrease glenohumeral (GH) horizontal adduction, leading to excessive GH horizontal abduction. However, few studies have examined this direct relationship, and none have investigated the ST internal rotation angle at stride foot contact (FC) and MER. This study investigated the relationships between GH horizontal adduction and ST internal rotation angles at MER and between ST internal rotation angles at FC and MER. MethodsWe recruited 15 asymptomatic collegiate baseball pitchers and assessed the ST internal rotation angle at FC and MER and GH horizontal adduction angle at MER during pitching using an optical motion tracking system. Pearson’s correlation coefficients determined the relationships between GH horizontal adduction and ST internal rotation angles at MER and between ST internal rotation angles at FC and MER. ResultsThe GH horizontal adduction angle at MER was significantly related to the ST internal rotation angle at MER (r = -0.58, p = 0.022). The ST internal rotation angle at FC was significantly related to the ST internal rotation angle at MER (r = 0.53, p = 0.045). ConclusionsThe GH horizontal adduction angle at MER is associated with the ST internal rotation angle at MER in asymptomatic collegiate baseball pitchers and the ST internal rotation angle at FC is related to the ST internal rotation angle at MER. Thus, the scapula and humerus should be controlled from FC to MER during pitching to reduce internal impingement risk in asymptomatic baseball pitchers.

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 240Hz, 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.

Correlation between run-up speed and throwing distance of elite javelin athletes

&lt;p&gt;目的：本研究探討台灣優秀標槍選手助跑速度與投擲距離之相關性。方法：8位國內優秀標槍選手 (身高：176.2 &amp;plusmn; 4.5公分，體重：87.7 &amp;plusmn; 10.7公斤，年齡：21.1 &amp;plusmn; 3.7歲，平均投擲距離：68.8 &amp;plusmn; 6.9公尺)，本研究採用實際比賽進行數據收集，本研究使用高速攝影機 (60Hz) 紀錄投擲標槍助跑過程，透過影像分析獲得助跑距離及時間。本研究採用相依樣本t檢定比較預賽及決賽的助跑速度及投擲表現及使用皮爾森積差相關分析比較助跑速度及投擲表現之相關性，顯著水準訂為 &amp;alpha; = .05。結果：研究結果發現，預賽與決賽的投擲表現顯著大於決賽有顯著差異 (p &lt; .05)，但預賽與決賽的助跑速度無顯著差異 (p &gt; .05)，另外，預賽與決賽的投擲距離與助跑速度相關性沒有顯著差異。結論：當助跑速度越快不會增加投擲距離。選手可能會有個別最佳的助跑速度。&lt;/p&gt;&lt;p&gt;The standing throw with run-up is the best approach to evaluate the performance of energy transfer and the efficiency of throwing motions for handball players. Purpose: This research aims at analyzing the usage of the standing throw with run-up among the handball players in Taiwan. The roles of body kinematics, strength of core muscles and standing balance of the drive leg played in the standing throw with run-up are also discussed. Methods: Nine Division I handball players from college went through a series of tests. The motions and the speed of the handball throwing were detected by a 3D electromagnetic motion analysis system and a sports radar gun, respectively. The maximum isometric muscle strength of trunks and hips were measured by a torque sensor and a home-made device of strength measurement. The standing balance of the drive leg was measured by a force plate with a mat. Results: The maximal shoulder external rotation angle in the arm cocking phase, the maximal trunk rotation velocity in the arm acceleration phase and the maximal shoulder horizontal adduction velocity showed moderate positive relationships with the ball velocity. The strength of back muscles had a moderate negative relationship with the ball velocity. The correlation between the balance ability of the drive leg and the ball velocity was not observed. Conclusion: The importance of proximal segments to the standing throw with run-up is analyzed by kinematical analysis. It is suggested that the energy of handball throwing is generated by the upper extremities or other limb segments in the processes of the standing throw with run-up. Our findings can serve as a helpful reference for both coaches and players.&lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;

Poster 107: Biomechanical Effect of “AIGHL Reconstruction” for Bankart Lesion in Thrower’s Shoulder: A Novel Surgical Treatment to Maintain Maximum Shoulder External Rotation Angle after Surgery

Objectives: For anterior shoulder instability, antero-inferior labral repair (Bankart repair) is a reliable surgery to prevent shoulder dislocation. However, in biomechanical and clinical studies, maximum shoulder external rotation angle is reported to be decreased by about 10 degrees due to shortening of the anterior band of the inferior glenohumeral ligament (AIGHL) length after Bankart repair. For overhead throwing athletes, the 10 degrees reduction in shoulder external rotation makes it difficult to return to the previous performance level, although it does not affect daily activity. To prevent shortening of the AIGHL length, an AIGHL reconstruction was developed using fascia lata graft. Preliminary clinical results in overhead throwing athletes showed that a throwing program could start with complete restoration of maximum shoulder external rotation angle 3 months after AIGHL reconstruction. In this study the effect of AIGHL reconstruction on shoulder external rotation and anterior stability for simulated Bankart lesion in a cadaveric model of a thrower’s shoulder was evaluated (Fig. 1). Methods: Eight cadaveric shoulders were tested at 60° of glenohumeral abduction (90° of shoulder abduction) to simulate throwing motion. Glenohumeral translations at 60° and 90° of external rotation, maximum humeral rotational range of motion, and humeral head shift were measured using goniometer and MicroScribe 3D-digitizer. Each specimen was subjected to five experimental stages: (1) intact condition; (2) simulation of thrower’s shoulder by anterior capsular stretching based on previously reported method; (3) creation of Bankart lesion (AIGHL and the labrum were detached at glenoid side); (4) Bankart repair using three suture anchors; and (5) AIGHL reconstruction using allograft of fascia lata. In the AIGHL reconstruction, allograft was patched between the detached AIGHL and glenoid at maximum shoulder external rotation position to restore the original AIGHL length (Fig. 2). For statistical analysis, linear mixed-effects model and Tukey’s post-hoc analysis were used. Results: After 20% stretching, shoulder external rotation and anterior translation were significantly increased (intact 128.3° and 2.8mm, thrower’s shoulder 141.9° and 7.3mm, p&lt;0.001). Creation of Bankart lesion significantly increased anterior translation (8.3mm) compared with intact condition (p=0.021). Bankart repair completely restored anterior translation (3.0mm) to intact level; however, maximum shoulder external rotation angle after Bankart repair (134.8°) was significantly less than that in thrower’s shoulder (p=0.009). AIGHL reconstruction completely restored anterior translation (6.5mm) to thrower’s shoulder without decreasing maximum shoulder external rotation angle (144.4°) compared with thrower’s shoulder (Fig. 3 &amp; 4). At maximum humeral external rotation, the humeral head was significantly shifted superiorly after creation of Bankart lesion compared with intact condition(p=0.005). After Bankart repair, the humeral head was significantly shifted inferiorly from the Bankart lesion (p=0.003) and was significantly inferior relative to the position after AIGHL reconstruction (p=0.007). Conclusions: While Bankart repair completely restored anterior translation to the intact level (tighter than thrower’s shoulder), AIGHL reconstruction completely restored to the thrower’s level. Furthermore, maximum shoulder external rotation angle was maintained after AIGHL reconstruction although Bankart repair decreased external rotation significantly. Therefore, AIGHL reconstruction can be a useful surgical option for Bankart lesion in overhead throwing athletes to restore anterior stability while maintaining maximum shoulder external rotation angle after surgery.

Comparison of Pitching Kinematics between Normal-Weight and Overweight Group in High School Baseball Pitchers

This study compared differences in pitching kinematics between normal-weight and overweight high school baseball pitchers. Twenty male pitchers were included in the study. According to the 2020 guidelines on the Body Mass Index (BMI) standard for children and adolescents by the Korean Society for the Study of Obesity, 10 participants with BMI below the 85% percentile were assigned to the normal-weight group, and 10 participants with BMI above the 85% percentile were assigned to the overweight group. The two groups threw 10 trials for a fastball with maximum effort. Out of 10 trials, three pitches thrown in the strike zone with the fastest velocity were extracted. The mean ball velocity was measured, and the mean and maximum angle and angular velocity of the knee, pelvis, trunk, shoulder, and elbow joints were calculated. The differences in the ball velocity, angle, and angular velocity between the two groups were compared using an independent t-test (p&lt;0.05). There were no differences in mean ball velocity between the two groups. However, compared with the normal-weight group, the overweight group showed smaller knee flexion, trunk forward tilt, trunk rotation, maximum trunk angular velocity, shoulder external rotation and maximum shoulder external rotation, while shoulder abduction and maximum elbow flexion were greater. These results suggest that the overweight group may have a high risk of soft tissue damage in the knee, shoulder, and elbow joints caused by limited movement of the trunk and inefficient movement between the extremities during power pitching.

Effects of Repetitive Pitching on Trunk Muscle Endurance and Thoracic and Shoulder Kinematics.

Baseball players are aware of the potential of shoulder problems due to repetitive throwing. However, few studies have examined how pitching repeatedly affects the thoracic spine and shoulder. This study aimed to determine the effects of pitching repeatedly on the endurance of trunk muscles and kinematics of the thoracic spine and shoulder. Cohort study. Trunk muscle endurance was assessed in flexion, extension, and lateral flexion positions in 12 healthy amateur baseball players. The positions of stride foot contact (SFC) during the early cocking phase and maximal shoulder external rotation (MER) during the late cocking phase were used to compute the thoracic and shoulder kinematics in degrees. Participants were then asked to throw 135 fastballs (~9 innings with 15 throws per inning). Throwing motions were monitored throughout the first, seventh, eighth, and nine innings, whereas trunk muscular endurance was assessed before and after the repetitive throwing activity. Ball speed during pitching was measured using a radar gun. All outcome measures were statistically compared to examine differences over time. The trunk muscle endurance declined after the throwing task. In the eighth inning, compared with the first inning, the thoracic rotation angle at the SFC increased toward the throwing side. In contrast, the shoulder horizontal adduction angle at MER decreased in the seventh and ninth innings. With repeated pitching, trunk muscle endurance gradually declines, and repetitive throwing significantly altered kinematics of the thoracic rotation at SFC and shoulder horizontal plane at MER. 2a.

The biomechanical analysis of the standing throw with run-up

&lt;p&gt;為了解手球選手在投擲動作上的效率，墊步射門是檢視能量傳遞好壞的最佳方式。目的：分析臺灣手球選手使用墊步射門的情形，以及探討肢體運動學，核心肌群肌肉力量和前導腳站立平衡能力在墊步射門中的重要性。方法：9 位大專男子甲組選手 (年齡 22.0 &amp;plusmn; 1.3 歲、身高 177.1 &amp;plusmn; 3.1 公分、體重 78.4 &amp;plusmn; 5.1 公斤)，以三度空間電磁場動作分析系統擷取墊步射門動作，並以雷達測速槍測量球速；以力矩傳感器搭配特製測力裝置測量軀幹及髖關節各肌群之最大等長肌力；以軟墊置於測力板上測量前導腳站立平衡能力。使用肯德爾相關係數探討射門運動學參數、核心肌群肌肉力量和前導腳站立平衡能力與墊步射門球速之相關性，顯著水準定在 p &lt; .05。結果：引臂期的肩膀最大外轉角度 (Kendall’s tau-b = .54)，手臂加速期的軀幹最大旋轉速度 (Kendall’s tau-b = .54)、肩膀最大水平內收速度 (Kendall’s tau-b = .69) 與射門球速皆有中度的正相關。背部肌肉力量與射門球速有中度的負相關 (Kendall’s tau-b = -.57)。前導腳平衡能力參數與射門球速皆無相關性存在。結論：透過運動學分析了解到大專男子甲組選手在執行墊步射門時的動作表現，並發現身體近端對於墊步射門的重要性。建議應加強墊步射門時的軀幹動作，藉由較快的軀幹旋轉速度來帶動上肢的投擲表現，以提升射門球速。&lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;&lt;p&gt;The standing throw with run-up is the best approach to evaluate the performance of energy transfer and the efficiency of throwing motions for handball players. Purpose: This research aims at analyzing the usage of the standing throw with run-up among the handball players in Taiwan. The roles of body kinematics, strength of core muscles and standing balance of the drive leg played in the standing throw with run-up are also discussed. Methods: Nine Division I handball players from college went through a series of tests. The motions and the speed of the handball throwing were detected by a 3D electromagnetic motion analysis system and a sports radar gun, respectively. The maximum isometric muscle strength of trunks and hips were measured by a torque sensor and a home-made device of strength measurement. The standing balance of the drive leg was measured by a force plate with a mat. Results: The maximal shoulder external rotation angle in the arm cocking phase, the maximal trunk rotation velocity in the arm acceleration phase and the maximal shoulder horizontal adduction velocity showed moderate positive relationships with the ball velocity. The strength of back muscles had a moderate negative relationship with the ball velocity. The correlation between the balance ability of the drive leg and the ball velocity was not observed. Conclusion: The importance of proximal segments to the standing throw with run-up is analyzed by kinematical analysis. It is suggested that the energy of handball throwing is generated by the upper extremities or other limb segments in the processes of the standing throw with run-up. Our findings can serve as a helpful reference for both coaches and players.&lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;

Validation of pitchAITM markerless motion capture using marker-based 3D motion capture

ABSTRACT This study sought to compare and validate baseball pitching mechanics, including joint angles and spatiotemporal parameters, from a single camera markerless motion capture solution with a 3D optical marker-based system. Ten healthy pitchers threw 2–3 maximum effort fastballs while concurrently using marker-based optical capture and pitchAITM (markerless) motion capture. Time-series measures were compared using R-squared (r2), and root mean square error (RMSE). Discrete kinematic measures at foot plant, maximal shoulder external rotation, and ball release, plus four spatiotemporal parameters were evaluated using descriptive statistics, Bland-Altman analyses, Pearson’s correlation coefficients, p-values, r2, and RMSE. For time-series angles, r2 ranged from 0.69 (glove arm shoulder external rotation) to 0.98 (trunk and pelvis rotation), and RMSE ranged from 4.37° (trunk lateral tilt) to 20.78° (glove arm shoulder external rotation). Bias for individual joint angle and spatiotemporal parameters ranged from −11.31 (glove arm shoulder horizontal abduction; MER) to 12.01 (ball visible). RMSE was 3.62 m/s for arm speed, 5.75% height for stride length and 21.75 ms for the ball visible metric. pitchAITM can be recommended as a markerless alternative to marker-based motion capture for quantifying pitching kinematics. A database of pitchAITM ranges should be established for comparison between systems.

Paper 35: High School and Professional Pitchers with Early Excessive Ipsilateral Trunk Tilt: A Newly Characterized Parameter for Biomechanical Evaluation

Objectives:Though contralateral trunk tilt has been frequently studied in baseball pitchers, the phenomena of excessive ipsilateral trunk tilt has not been explored as a potential correlate with throwing arm kinetics. Excessive ipsilateral trunk tilt is often observed during earlier portions of the pitch cycle. High school pitchers with excessive contralateral trunk tilt during the late cocking phase of pitching have been noted to have significantly faster ball velocity, as well as increased elbow distraction force, shoulder distraction force, elbow varus torque, and shoulder internal rotation torque. Collegiate pitchers with excessive contralateral trunk tilt at maximum shoulder external rotation and at ball release have significantly faster ball velocity and higher elbow varus torque. The purpose of this study was to evaluate the effect of ipsilateral and contralateral trunk tilt on kinetic and kinematic parameters among high school and professional baseball pitchers.Methods:Professional and high school baseball pitchers were assessed with 3D-motion capture technology (480 Hz) while pitching in a controlled laboratory setting. Pitchers were grouped into ipsilateral, neutral, or contralateral trunk tilt groups based on the degree of lateral trunk tilt at foot contact (FC) and ball release (BR) (Figure 1). Trunk and shoulder kinematics, as well as throwing arm kinetics, were compared between subgroups with post-hoc regression analysis.Results:Professional pitchers (n=287) had significantly higher ipsilateral trunk tilt at FC (p<0.001) compared to high school pitchers (n=59) (Figure 2). High school pitchers with excessive contralateral trunk tilt at BR experienced significantly higher shoulder superior force (27.0 ± 7.4 vs. 17.6 ± 5.1 %Body Weight [BW] respectively, p<0.001) and shoulder anterior force (39.6 ± 8.2 vs. 35.7 ± 5.4 %BW respectively, p<0.001) compared to the ipsilateral trunk tilt cohort, while accomplishing comparable ball velocity (30.2±3.2 vs. 30.4±2.1m/s, p=0.633). For professional pitchers, for every 10° increase in ipsilateral trunk tilt at FC, ball velocity increased by 0.2 m/s (B: 0.02, β: 0.07, SE: 0.005, p=0.010), while elbow varus torque (EVT) decreased by 0.1%BWxHeight (B: -0.01, β: -0.08, SE: 0.002, p<0.001) and shoulder internal rotation torque (SIRT) decreased by 0.1 %BWxHeight (B: -0.01, β: -0.07, SE: 0.002, p=0.005).Conclusions:High school and professional pitchers with excessive ipsilateral trunk tilt at FC consistently demonstrated significantly decreased throwing arm kinetics (high school: shoulder anterior force, shoulder superior force; professional: SIRT, EVT) compared to pitchers with excessive contralateral trunk tilt at BR, with at least equivalent ball velocity. In addition, professional pitchers already appear to engage in significantly greater ipsilateral trunk tilt at early portions of the pitch cycle when compared to high school pitchers, which may represent a kinetically favorable method adopted by pitchers at higher playing levels to maintain adequate ball velocity while concomitantly minimizing throwing arm kinetics. While contralateral trunk tilt has previously been associated with throwing arm kinetics in high school and collegiate pitchers, ipsilateral lateral trunk tilt has not been assessed in professional pitchers, a subgroup characterized by distinct pitching kinematics compared to amateur pitchers. Further research is warranted to determine if the kinetic impact of trunk tilt during the throwing motion of baseball pitchers impacts the risk of injury.UPLOAD-https://planion-client-files.s3.amazonaws.com/AOSSM/blobs/ada6d538-50e8-460e-ac42-c385825f1ce4/1/Trunk_Tilt_Fig_2.docx Figure 1.Lateral trunk till in pitchers; (+) indicates ipsilaleral trunk till, (-) indicates contralateral trunk tilt.

Paper 11: Utility of Objective Testing for Initiation of a Throwing Program Following Shoulder and Elbow Surgery in Competitive Baseball Players

Paper 11: Utility of Objective Testing for Initiation of a Throwing Program Following Shoulder and Elbow Surgery in Competitive Baseball Players

Relationships between throwing mechanics and shoulder anterior force in high school and professional baseball pitchers.

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. 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. 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). 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. : 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.

Relationship between scapular control during isometric shoulder flexion and scapular motion during baseball pitching: a cross-sectional study

BackgroundA baseball pitcher with decreased scapular control may not be able to achieve suitable scapular motion at maximum shoulder external rotation (MER) of baseball pitching during the pitching action. It is common clinically to compare scapular control of the throwing and non-throwing arms to detect side-to-side differences. However, it remains unclear whether scapular control is different between the throwing and non-throwing arms. Moreover, no data exist on the relationship between scapular control and scapular motion at MER of pitching. Primarily, this study aimed to compare scapular control during isometric shoulder flexion between the throwing and non-throwing arms. Secondly, this study aimed to investigate the relationship between scapular control during isometric shoulder flexion and scapular motion at MER of pitching.MethodsFifteen healthy collegiate baseball pitchers (age, 20.2 ± 1.9 years; height, 1.76 ± 0.05 m; body mass, 73.3 ± 6.7 kg) were recruited. An optical motion tracking system was used to assess scapular motion. Scapular control was defined as the amount of change in the scapular internal rotation angle, downward rotation angle, and anterior tilt angle during isometric shoulder flexion. We assessed scapular position at MER of pitching.ResultsNo significant differences were detected for any of the scapular angles during isometric shoulder flexion between the throwing and non-throwing arms. The amount of change in the scapular internal rotation angle, scapular downward rotation angle, and scapular anterior tilt angle during isometric shoulder flexion had a significant relationship with the scapular downward rotation angle at MER.ConclusionsNo side-to-side difference was noted in scapular control during isometric shoulder flexion in healthy collegiate baseball pitchers at the group level. Further studies are required to understand the side-to-side differences at the individual level. Additionally, there was a relationship between scapular control during isometric shoulder flexion and scapular position at MER. These findings suggest that clinicians may consider using isometric shoulder flexion to assess scapular control in baseball pitchers.

The Clinician's Guide to Baseball Pitching Biomechanics.

Improper baseball pitching biomechanics are associated with increased stresses on the throwing elbow and shoulder as well as an increased risk of injury. Previous studies quantifying pitching kinematics and kinetics were reviewed. Clinical review. Level 5. 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. Improved pitching biomechanics can increase performance and reduce risk of injury. Level C.

The role of the flexor pronator muscles as dynamic stabilizers against elbow valgus stress in patients with medial ulnar collateral ligament insufficiency.

The flexor pronator muscles (FPMs) have been reported to act as dynamic stabilizers against valgus forces in overhead-throwing athletes. Several studies have demonstrated the anatomic, biomechanical, and clinical effects of the FPMs. However, no studies have investigated the invivo kinematics of the FPMs against the valgus forces on the elbow. This study aimed to clarify the clinical contribution of the FPMs as dynamic stabilizers in medial ulnar collateral ligament (MUCL) insufficiency. Eighteen baseball players with MUCL injury participated in this study. The elbow was flexed to 90°, and the forearm was placed in the supinated position. Manual valgus stress was applied to the elbow joint until maximal shoulder external rotation was achieved. The width of the ulnohumeral joint space was measured using ultrasonography, and any changes in medial elbow pain were recorded before and after isometric forearm pronation. All the subjects had MUCL tenderness and felt medial elbow pain when elbow valgus stress was applied. The width of the medial joint space was significantly larger on the injured side than on the healthy side (5.1 ± 1.0 mm vs. 3.2 ± 1.0 mm) with elbow valgus stress. During isometric forearm pronation, the width of the medial joint space was significantly decreased (3.1 ± 0.9 mm vs. 2.6 ± 1.0 mm) and medial elbow pain had completely diminished. Isometric forearm pronation reduces valgus stress-induced widening of the medial joint space and medial elbow pain in patients with MUCL insufficiency.

Establishing the Role of Elbow Muscles by Evaluating Muscle Activation and Co-contraction Levels at Maximal External Rotation in Fastball Pitching.

Background: Baseball pitching is associated with a high prevalence of ulnar collateral ligament injuries, potentially due to the high external valgus load on the medial side of the elbow at the instant of maximal shoulder external rotation (MER). In-vitro studies show that external valgus torque is resisted by the ulnar collateral ligament but could also be compensated by elbow muscles. As the potential active contribution of these muscles in counteracting external valgus load during baseball pitching is unknown, the aim of this study is to determine whether and to what extent the elbow muscles are active at and around MER during a fastball pitch in baseball.Methods: Eleven uninjured pitchers threw 15 fastball pitches. Surface electromyography of six muscles crossing the elbow were measured at 2000 Hz. Electromyography signals were normalized to maximal activity values. Co-contraction index (CCI) was calculated between two pairs of the flexor and extensor elbow muscles. Confidence intervals were calculated at the instant of MER. Four ranges of muscle activity were considered; 0–20% was considered low; 21–40% moderate; 41–60% high and over 60% as very high. To determine MER, the pitching motion was captured with a highspeed camera at 240 Hz.Results: The flexor pronator mass, pronator teres, triceps brachii, biceps brachii, extensor supinator mass and anconeus show moderate activity at MER. Considerable variation between participants was found in all muscles. The CCI revealed co-contraction of the two flexor-extensor muscle pairs at MER.Interpretation: The muscle activation of the flexor and pronator muscles at MER indicates a direct contribution of forearm muscles crossing the medial side of the elbow in counteracting the external valgus load during fastball pitching. The activation of both flexor and extensor muscles indicates an in-direct contributory effect as the combined activity of these muscles counteract opening of the humeroulnar joint space. We believe that active muscular contributions counteracting the elbow valgus torque can be presumed to relieve the ulnar collateral ligament from maximal stress and are thus of importance in injury risk assessment in fastball pitching in baseball.

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.