Shoulder Internal Rotation Torque Research Articles

Kinematic and Kinetic Comparisons of Arm Slot Position Between High School and Professional Pitchers.

Throwing arm kinetics differ in pitchers at varying arm slot (AS) positions (frontal-plane arm position at ball release relative to the vertical axis). To determine how kinematic and kinetic values differ between professional and high school pitchers with varying AS positions, and whether these differences are similarly observed in both populations. High school (n = 130) and professional (n = 288) pitchers threw 8 to 12 fastballs under 3-dimensional motion capture technology. Pitchers in each cohort were subdivided based on mean AS position at ball release: AS1 (least degree of AS: most overhand throwing styles), AS2 (intermediate degree of AS: three-quarter throwing styles), or AS3 (greatest degree of AS: most sidearm throwing styles). Kinetic and kinematic parameters were compared between groups. Controlled laboratory study. High school pitchers had a more overhand AS at ball release (50° ± 11°) compared with professional pitchers (58° ± 14°) (P < .001). In both cohorts, AS1 pitchers had significantly greater shoulder abduction (high school, P <0.001; professional, P <0.0001) and lateral trunk flexion (high school, P < 0.001; professional, P <0.0001) at ball release compared with AS3 pitchers. Professional pitchers with an AS3 position had significantly delayed timing of maximum upper trunk angular velocity compared with AS1 pitchers (64% ± 7% vs 57% ± 7% of pitch time, respectively; P < .0001). A significant positive correlation between AS and elbow flexion torque was found in high school pitchers (P = .002; β = 0.28), and a significant negative correlation between AS and elbow varus torque (P < .001; β = -0.22) and shoulder internal rotation torque (P < .001; β = -0.20) was noted in professional pitchers. AS position was related to shoulder abduction and trunk lateral tilt. Professional and high school pitchers with varying AS positions did not experience similar changes in throwing arm kinetics. In professional pitchers, the earlier onset of maximum upper trunk angular velocity with overhand throwing style may reflect inappropriate pelvis-trunk timing separation, a parameter implicated in upper extremity injury, and the negative correlation between AS and elbow varus and shoulder internal rotation torque suggests that both excessive and minimal AS positions have negative implications.

Mechanism for control of ball spin rate by the upper limb in baseball pitching based on singular value decomposition

This study aims to examine the mechanism by which the ball spin rate during fastball pitching is controlled by synergistic joint torque. The participants were seven baseball players. The kinematics and kinetics of the fingers, wrist, elbow, and shoulder were calculated using the inverse dynamics method. The synergistic relationship between the joint torques was calculated using singular value decomposition. The similarity of the spatial pattern of the joint torque in each participant was evaluated using cosine similarity. The results indicated that there were three types of synergistic torque control: (1) two pitchers had a synergistic torque control that was primarily based on shoulder internal rotation torque, (2) two pitchers had a synergistic torque control that was primarily based on elbow extension torque, and (3) three pitchers had a synergistic torque control that was primarily based on shoulder horizontal adduction torque. In particular, pitchers with a high spin rate relative to the ball velocity (SPV) had a torque control of the shoulder internal rotation type. In contrast, pitchers with a low SPV had a torque control of the shoulder horizontal adduction type. It is considered that pitchers with a high SPV execute shoulder internal rotation torque, which has the same direction as that of ball spin, based on hierarchical control to increase the ball spin rate. These results suggest that pitchers with high and low SPVs exhibit different motor patterns. Pitchers and coach need to focus on the shoulder joint as well as the fingers when they throw fastball.

Clinical shoulder measurements related to joint loads in collegiate pitchers

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. 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. 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. 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.

The influence of excessive ipsilateral trunk tilt on upper-extremity throwing mechanics: a newly characterized parameter for biomechanical evaluation in high school and professional pitchers.

Although contralateral trunk tilt has been recognized, the phenomenon of excessive ipsilateral trunk tilt, often observed during earlier portions of the pitch, has not been explored as a potential correlate with throwing-arm kinetics among baseball pitchers. The purpose of this study was to evaluate kinetic and kinematic parameters among high school and professional pitchers related to excessive ipsilateral and contralateral trunk tilt. Professional and high school pitchers were assessed with a 3-dimensional motion capture system (480 Hz) while pitching. Pitchers were grouped as follows: excessive ipsilateral tilt at foot contact (FC), neutral, or excessive contralateral tilt at ball release (BR). Trunk and shoulder kinematics as well as throwing-arm kinetics were compared between subgroups via post hoc regression analysis. Professional pitchers (n=287) had significantly higher ipsilateral trunk tilt at FC (P<.001) than high school pitchers (n=59). High school pitchers with excessive contralateral trunk tilt at BR experienced significantly higher shoulder superior force (27.0%±7.4% body weight [BW] vs. 17.6%±5.1% BW, P<.001) and shoulder anterior force (39.6%±8.2% BW vs. 35.7%±5.4% BW, P<.001) compared with the ipsilateral trunk tilt cohort but had comparable ball velocity (30.2±3.2 m/s vs. 30.4±2.1 m/s, P=.633). For professionals, for every 10° increase in ipsilateral trunk tilt at FC, ball velocity increased by 0.2 m/s (B = 0.02, β = 0.07, standard error [SE] = 0.005, P= .010) whereas elbow varus torque decreased by 0.1% BW × height (B = -0.01, β = -0.08, SE = 0.002, P<.001) and shoulder internal rotation torque decreased by 0.1% BW × height (B = -0.01, β = -0.07, SE = 0.002, P= .005). High school and professional pitchers with excessive ipsilateral trunk tilt at FC consistently demonstrated significantly decreased throwing-arm kinetics (shoulder anterior force and shoulder superior force for high school pitchers and shoulder internal rotation torque and elbow varus torque for professional pitchers) compared with pitchers with excessive contralateral trunk tilt at BR, with equivalent ball velocity. In addition, professional pitchers appeared to engage in significantly greater ipsilateral trunk tilt during early portions of the pitch when compared with 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.

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.

Pitching Mechanics and the Relationship to Accuracy in Professional Baseball Pitchers

Background: Biomechanical predictors of pitching accuracy are underevaluated in baseball research. It is unclear how pitchers with higher accuracy differ in terms of kinematics and upper extremity kinetics. Purpose: To differentiate high- and low-accuracy professional pitchers by full-body kinematic and upper extremity kinetic parameters. Study Design: Descriptive laboratory study. Methods: In total, 121 professional baseball pitchers threw 8 to 12 fastballs while assessed with motion-capture technology (480 Hz). Pitchers were divided into high-accuracy (n = 33), moderate-accuracy (n = 52), and low-accuracy (n = 36) groups based on the absolute center deviation of each pitcher’s average pitch to the center of the pitching chart by greater or less than 0.5 SD from the mean, respectively. The 95% confidence ellipses with comparisons of major and minor radii and pitching probability density grids were constructed. Analysis of variance was used to compare kinematic and kinetic values between groups. Results: The absolute center deviation (14.5% ± 6.7% vs 33.5% ± 3.7% grid width; P < .001) was significantly lower in the high-accuracy compared with the low-accuracy group, with no significant difference in ball velocity (38.0 ± 1.7 vs 38.5 ± 2.0 m/s; P = .222). Lead knee flexion at ball release (30.6°± 17.8° vs 40.1°± 16.3°; P = .023) was significantly less for the high-accuracy pitchers. Peak normalized shoulder internal rotation torque (5.5% ± 1.0% vs 4.9% ± 0.7% body weight [BW] × body height [BH]; P = .008), normalized elbow varus torque (5.4% ± 1.0% vs 4.8% ± 0.7% BW × BH; P = .008), and normalized elbow medial force (42.9% ± 7.3% vs 38.6% ± 6.2% BW; P = .024) were significantly greater for the low-accuracy group compared with the high-accuracy group. Conclusion: Professional pitchers with increased accuracy experienced decreased throwing arm kinetics. These pitchers had increased lead knee extension at later stages of the pitch, potentially providing more stable engagement with the ground and transference of kinetic energy to the upper extremities. Professional pitchers can consider increasing lead knee extension at the final stages of the pitch to improve the accuracy of their throws and mitigate elbow varus torque. Clinical Relevance: Increased elbow varus torque, shoulder internal rotation torque, and elbow medial force in less accurate pitchers may contribute to increased injury risk in this group.

Increased Shoulder Distraction Force and Shoulder Horizontal Abduction in Professional Baseball Pitchers With Discordant Torso Rotation Order

Background: Inefficient energy transfer from the pelvis and trunk has been shown to increase compensation at the level of the shoulder. Kinetic chain sequencing of the core segments is underexamined in professional baseball pitchers, especially as it relates to changes in upper extremity kinetics. Purpose: To evaluate elbow and shoulder kinetics in a cohort of professional pitchers differentiated by instances of discordant pelvic to upper torso sequencing during the pitch. Study Design: Descriptive laboratory study. Methods: 285 professional baseball pitchers were evaluated using 3D motion capture (480 Hz). Pitchers were divided into “chronological” and “discordant” groups based on whether maximum pelvic rotation velocity occurred before (chronological) or after (discordant) maximum upper torso rotation velocity during the pitch motion. Pelvic, upper torso, and shoulder kinematic parameters, shoulder distraction force, shoulder internal rotation torque, and pitch efficiency (PE) were compared between groups. Results: Pitchers with discordant torso sequencing (n = 30; 110 pitches) had greater shoulder horizontal adduction at maximum external rotation (mean difference, 3.6°; 95% CI, −5.2° to −2.0°; t = −4.5; P < .001) and greater maximum shoulder external rotation (mean difference, 3.7°; 95% CI, 5.7° to 1.5°; t = −3.5; P < .001) than chronological pitchers (n = 255; 2974 pitches). PE did not differ between groups (P = .856), whereas ball velocity was significantly faster in the discordant group (mean difference, 0.6 m/s; 95% CI, −1.1 to −0.3 m/s; t = −3.3; P = .0012). Chronological pitchers had significantly reduced shoulder distraction force (mean difference, −4.7% body weight (BW); 95% CI, −7.9% to −1.5% BW; t = −2.9; P = .004) with no difference in shoulder internal rotation torque (P = .160). These kinematic and kinetic differences were not observed when accounting for interpitcher variability. Conclusion: Between pitchers, those who had a discordant pelvic to upper torso sequence experienced significantly greater shoulder distraction forces, potentially compensating by increasing maximum shoulder external rotation and horizontal abduction. Achieving maximal pelvic rotation velocity before maximal rotation velocity may be advantageous in preventing compensation at the upper extremity and excessive throwing arm loading. Clinical Relevance: Identifying risk factors for increased upper extremity forces has potential implications in injury prevention. Specifically, mitigating shoulder distraction forces may be beneficial in reducing risk of injury.

Association of Pitch Timing and Throwing Arm Kinetics in High School and Professional Pitchers

Background: Understanding the relationship between the temporal phases of the baseball pitch and subsequent joint loading may improve our understanding of optimal pitching mechanics and contribute to injury prevention in baseball pitchers. Purpose: To investigate the temporal phases of the pitching motion and their associations with ball velocity and throwing arm kinetics in high school (HS) and professional (PRO) baseball pitchers. Study Design: Descriptive laboratory study. Methods: PRO (n = 317) and HS (n = 54) baseball pitchers were evaluated throwing 8 to 12 fastball pitches using 3-dimensional motion capture (480 Hz). Four distinct phases of the pitching motion were evaluated based on timing of angular velocities: (1) Foot-Pelvis, (2) Pelvis-Torso, (3) Torso-Elbow, and (4) Elbow-Ball. Peak elbow varus torque, shoulder internal rotation torque, and shoulder distraction force were also calculated and compared between playing levels using 2-sample t tests. Linear mixed-effect models with compound symmetry covariance structures were used to correlate pitch velocity and throwing arm kinetics with the distinct temporal phases of the pitching motion. Results: PRO pitchers had greater weight and height, and faster ball velocities than HS pitchers (P < .001). There was no difference in total pitch time between groups (P = .670). PRO pitchers spent less time in the Foot-Pelvis (P = .010) and more time in the Pelvis-Torso (P < .001) phase comparatively. Shorter time spent in the earlier phases of the pitching motion was significantly associated with greater ball velocity for both PRO and HS pitchers (Foot-Pelvis: B = −6.4 and B = −11.06, respectively; Pelvis-Torso: B = −6.4 and B = −11.4, respectively), while also associated with increased shoulder proximal force (Pelvis-Torso: B = −76.4 and B = −77.5, respectively). Decreased time in the Elbow-Ball phase correlated with greater shoulder proximal force for both cohorts (B = −1150 and B = −645, respectively) with no significant correlation found for ball velocity. Conclusion: Significant differences in temporal phases exist between PRO and HS pitchers. For all pitchers, increased time spent in the final phase of the pitching motion has the potential to decrease shoulder distraction force with no significant loss in ball velocity. Clinical Relevance: Identifying risk factors for increased shoulder and elbow kinetics, acting as a surrogate for loading at the respective joints, has potential implications in injury prevention.

Influence Of Back Foot Orientation On Kinetics And Kinematics During Baseball Pitching

The objective of pitching is to generate the most speed, accuracy, and efficiency as possibly in every pitch. The pitching motion is a kinetic chain, where the lower extremity and trunk generate force during the wind up and stride phase which is transferred to the ball through the shoulder and elbow. PURPOSE: The purpose of this study was to assess the back foot orientation’s influence on ball velocity and injury risk. A secondary purpose was to see if the back foot orientation has a relationship to different aspects of the kinetic chain. METHODS: The data examined was from seventeen collegiate baseball pitchers (age = 20.4 ± 1.2 years, height = 1.87 ± 0.05 m, mass = 94 ± 7 kg). One representative fastball pitch was extracted in this study in which 3D motion data was collected utilizing a 38 reflective marker set and a 12-camera motion analysis system at a sampling rate of 400 Hz. Back foot orientation data was extracted at maximum knee height of the stride leg during the stride phase. Statistical analyses were conducted in SPSS 25.0 using bivariate pearson correlation coefficients analysis. RESULTS: Back foot orientation data was collected at knee high of the stride leg (98.8 ± 6.2). There were no significant interactions between backfoot orientation and ball velocity or injury risk. Back foot orientation with respect to ball velocity resulted in a p-value of 0.160, indicating that there was no relationship between these variables in the data collected. Back foot orientation with respect to MEVT (injury risk) and MSIRT (maximal shoulder internal rotation torque) resulted in p-values of .718 and .896, respectively, which also indicated that there was not a significant relationship between these variables in the data collected. There was a significant association (r2 = 0.25, p = 0.041) between backfoot orientation and RPVZ_WORK_RFA (induced work of the forearm by pelvic rotation). CONCLUSIONS: The research conducted in this study was the first to look at foot orientation during pitching. The information gained is a starting point to see how backfoot orientation influences the kinetic chain. Although there were no statistically significant interactions between back foot orientation and ball velocity, MEVT, and MSIRT, there was a significant interaction with the mechanical energy transferred to the right forearm from pelvic rotation.

The association of stride length to ball velocity and elbow varus torque in professional pitchers

ABSTRACT Professional basebal pitchers (n =315) were divided into quartiles based on increasing stride length and random intercept linear mixed-effect models were used to correlate stride length with ball velocity, pelvis and trunk rotation at foot contact, and throwing arm kinetics. Average stride length among all pitchers was 78.3±5.3%body height (%BH). For every 10% increase in stride length, ball velocity increased by 0.9 m/s (B =0.089, β =0.25, p <0.001) and trunk rotation initiation occurred 4.23 ms earlier (B =−0.42, β =−0.14, p <0.001). When divided into quartiles pelvis rotation was less towards home plate in Q1 compared to Q3 and Q4 (70.0±10.7° vs. 60.9±8.9° and 58.6±9.1°, p <0.001). No significant differences in shoulder internal rotation torque (p =0.173) or elbow varus torque (p =0.072) were noted between quartiles. Professional baseball pitchers who reached stride lengths of 80%BH or greater achieved faster ball velocity without an increase in elbow varus torque. This may, be a byproduct of rotating the pelvis for a greater proportion of the pitching motion and thereby more effectively utilising the lower extremities in the kinetic chain. Encouraging players to achieve this threshold of stride length may enhance ball velocity outcomes.

The Science and Biomechanics of Long-Toss

Overhead throwing is a particularly violent motion that requires a complex sequence of timed muscle activations to efficiently transfer energy up the kinetic chain to throw a ball. Long-toss has long been utilized as a means of increasing shoulder range of motion, strength, and endurance, as well as an important component of rehabilitation in interval throwing programs. The purpose of this review is to assess the current literature on the science and biomechanics of long-toss. While long-toss is ubiquitously utilized in throwing programs for pitchers of all ages, the definition of long-toss, as well as its primary function in a throwing program, is debated. Throwing biomechanics in long-toss differ from that of mound pitching, although much of the variation is determined by the type of long-toss: shorter distance and on a line versus maximum distance and not on a line. Biomechanical factors including the kinematic changes of increased maximum glenohumeral external rotation, increased maximum elbow flexion, decreased trunk forward flexion at front foot contact, kinetic changes of increased shoulder internal rotation torque, increased elbow varus torque, and increased elbow extension velocity can occur with maximum distance long-toss throwing. Long-toss is a highly variable training supplement that is used in throwing programs at all levels of baseball competition. Current literature has demonstrated a number of kinetic and kinematic changes in the throwing arm and throwing motion related to increasing long-toss distances. However, the exact benefits of long-toss are difficult to quantify due to the numerous definitions and various utilizations of long-toss.

Kinetics Analysis of Overhead Standing Smash in Badminton

The purpose of this study was to analyze the joint motion kinetics of the shoulders, elbows, and wrists between experienced player (skilled player) group and unskilled player group when performing overhead standing smash in badminton game. The samples involved were 26 samples. The samples included 13 male badminton players joining Student Activity Unit who had achieved many achievements and had a high skill (skilled), while the other 13 samples were unskilled players, involving students who had just studied under one year. The mean of participants’ age was 19.4 ± 1.6 years, height was 1.73 ± 0.12m, and body weight was 62.8 ± 3.7kg. This study used 3 Panasonic Handycams, a calibration set, 3D Frame DIAZ IV motion analysis software, and a speed radar gun. Normalization of the kinetic motion score of the shoulder, elbow, and wrist joints was calculated using the inverse dynamics method. The t-test was used to determine the significance of motion kinetic difference of the two different groups. The results presented that the shuttlecock speed of the skilled player group, during the overhead standing smash, showed a significant difference. Meanwhile, the joint motion of the inferior shoulder force, shoulder anterior force, shoulder internal rotation torque, shoulder horizontal abduction torque, elbow anterior force, and wrist flexion torque were higher in the skilled players group than the unskilled player group.

ANALYSIS OF TRUNK POWER AND JOINT STRESSES BETWEEN PROFESSIONAL AND COLLEGIATE PITCHERS

The dynamic motion of a baseball pitch generates high elbow and shoulder torques that can result in injury. Previous research has noted the importance of properly transferring energy from the lower extremities through the throwing arm to decrease joint stress. The goal of this study was to compare segmental powers between two levels of pitchers at various moments throughout the pitching cycle and observe their influence on upper extremity torques. Thirteen professional and thirteen collegiate pitchers participated in this study. Forty-seven reflective markers were attached to the subjects at specific landmarks. An 8-camera motion analysis system was set up surrounding an artificial pitching mound, where participants threw 10 fastballs. Data were exported and processed using Visual 3D software. Welch’s T-tests compared the means between groups with a significance set at p &lt; 0.05. Professional pitchers were found to have significantly greater torso power at foot contact, maximum shoulder external rotation, ball release, and overall peak torso power. They also demonstrated significantly greater pitch velocity. Professional pitchers generated similar elbow varus torque and shoulder internal rotation torque compared to collegiate pitchers. These findings suggest professional pitchers more effectively use torso power to help increase pitch speed without increasing overall joint torques.

Arm abduction angle at ball release influences shoulder forces and torques during the windmill softball pitch

Objectives:Shoulder pain and ligamentous injury is a common complaint among fast pitch softball pitchers. In addition to extreme shoulder joint motion during pitch delivery, sudden deceleration immediately after ball release places increased stress across the shoulder joint. Some pitchers release the ball with the throwing arm tucked close to the trunk, while others let the arm float outwards in a more abducted position. The position of the arm at ball release (BR) may be key to the mechanism of shoulder pain. Previous work demonstrated that during the change up pitch, softball pitchers with upper extremity pain demonstrated greater shoulder abduction at stride and less trunk lateral flexion at BR compared to athletes without pain (Oliver et al 2018). The purpose of this study was to test the hypothesis that placement of the arm closer to the trunk (shoulder adduction) at ball release will produce less shoulder stress during fastball windmill pitches.Methods:Twenty-six female fast pitch softball pitchers with a mean age of 18 +/- 6 y, including 16 high school, 7 collegiate, and 3 professional athletes, underwent 3D biomechanical pitch analyses using 20 Vicon high-speed motion capture cameras (240 hz). All pitchers threw the standard 13.11 m mound-to-plate distance at a strike zone target while a radar gun collected pitch speeds. The fastest, most accurate fastball pitches for each subject were selected for analyses (average of 5 pitches per subject). A total of 103 pitches were used to calculate: shoulder abduction angle and shoulder compression force during the BR phase (10 frames surrounding BR) and peak shoulder torques. Pearson correlations were performed to determine the relationship of shoulder frontal plane (adduction/abduction) angle during the ball release phase to these biomechanical measures.Results:The smallest abduction shoulder angle reached during the BR phase (avg: 14.06 +/- 6.71 degrees) demonstrated a significant positive correlation with shoulder compression force, p=0.008 and with peak flexion torque, p< 0.001 (Table 1). This shoulder abduction angle during the BR phase demonstrated negative correlations with peak shoulder adduction torque, p<0.001 and shoulder internal rotation torque, p< 0.001.Conclusion:These initial findings support the hypothesis that pitchers who release the ball with their arm close to their trunk demonstrate lower shoulder compression forces and shoulder flexion torques than those with a more abducted arm position. Future studies are needed to explore the interplay of pitching technique mechanics, shoulder joint stresses, and injury history to inform pitching instruction and injury prevention efforts.Table 1.The relationship between shoulder frontal plane angle during ball release with shoulder compression force and torquesMeasureAverage SDRPBall release phase peak shoulder compression force7.791.53 BW0.258*0.008Peak shoulder internal rotation torque-27.4528.65 Nm-0.377*P < 0.001Peak shoulder adduction torque-47.8649.59 Nm-0.479*P < 0.001Peak shoulder flexion torque60.7946.01 Nm0.530*P < 0.001*Established level of significance p<0.05

Impact of shoe and cleat type on youth baseball pitching biomechanics

ABSTRACT Shoulder and elbow injuries among baseball pitchers of various ages and abilities continue to rise despite exhaustive efforts analysing pitch type and count; however, it has yet been determined if footwear plays a role in altering pitching mechanics and subsequently injury susceptibility. Therefore, the purpose of the study was to investigate the effect footwear might have on youth baseball pitching mechanics. Data were collected on eleven youth baseball pitchers wearing two different shoes on two different surface inclinations. A repeated measures ANOVA was utilised to determine differences between upper and lower extremity joint kinematics and kinetics (p < 0.05). Results indicate wearing moulded cleats elicited significantly greater amounts of shoulder internal rotation torque, angle and velocity as well as elbow varus torque. Turf shoes caused an increased plantarflexion joint angle in the stride leg ankle and shoulder external rotation torque, angle and velocity. The findings of this study suggest that the footwear worn by a youth baseball pitcher does alter the shoulder and elbow dynamics in the dominant throwing arm as well as the amount of ankle plantarflexion in the stride leg.

The influence of mound height on baseball movement and pitching biomechanics

ObjectivesTo determine whether mound height is associated with baseball movement (velocity, spin and break) and baseball pitching biomechanics (kinematics and kinetics). DesignControlled laboratory study. MethodsTwenty collegiate baseball pitchers threw five fastballs and five curveballs from four different mound heights (15cm, 20cm, 25cm, 30cm) in a randomized order. Ball movement was computed by a ball tracking system, while pitching biomechanics were calculated with an 11-camera optical motion capture system. Repeated measures analysis of variance was utilized to detect significant differences among the four different mound heights (p<0.05) for the fastball and curveball pitches. ResultsThere were no significant differences observed for ball movement. There were seven significant kinematic differences for fastballs and eight kinematic differences for curveballs. Although these differences were statistically significant, the magnitudes were small, with most joint angles changing by less than 2°. There were no significant kinetic differences for curveballs, but five kinetic parameters (elbow varus torque, elbow flexion torque, elbow proximal force, shoulder internal rotation torque, and shoulder anterior force) varied with mound height for fastballs. In general, fastball kinetics were 1%–2% less from the lowered (15cm, 20cm) mounds than from the standard (25cm) or raised (30cm) mounds. ConclusionsLowering the mound may not affect a pitcher’s ball movement, but may slightly reduce shoulder and elbow kinetics, possibly reducing the risk of injury.

Biomechanical analysis of the “waiter’s serve” on upper limb loads in young elite tennis players

Waiter’s serve (WS) is a specific tennis serve posture frequently observed in young players, and commonly considered as a technical error by tennis coaches. However, biomechanical impact of WS is unknown. The aims of this study were to identify the potential consequences of WS in young elite players relating to performance and injury risk, and to explain the kinematic causes of WS. Serve of 18 male junior elite players (Top 10 national French ranking, aged 12–15 years) was captured with a 20 camera, 200 Hz VICON MX motion analysis system. Depending on their serve technique, the players were divided into two groups (WS versus Normal Serve [NS]) by experienced coaches. Injury data were collected for each player during a 12-month-period following the motion capture. Normalized peak kinetic values of the dominant arm were calculated using inverse dynamics. In order to explain WS posture, upper limb kinematics were calculated during the cocking and the acceleration phases of the serve. Shoulder internal rotation torque, wrist proximal and anterior forces (P < .05) and elbow varus torque (P < .01) were significantly higher in WS group, with no difference from NS group concerning serve velocity. Moreover, significant lower shoulder abduction and higher wrist extension (P < .05) were observed for WS players during the cocking phase. Even if no significant difference was found between groups concerning injuries, higher upper limb joint loads suggested WS could be considered as pathomechanical in young elite players and could lead to upper limb joint injuries.

Correlation of upper limb joint load withsimultaneous throwing mechanics including acceleration parameters in amateur baseball pitchers.

[Purpose] The purpose of this study was to provide information regarding the knowledge of mechanical principles related to the load applied to the shoulder and elbow during the pitching motion. [Subjects and Methods] The three-dimensional kinematics of body segments were measured in 19 amateur baseball players with a VICON motion capture system. The correlation between maximum shoulder internal torque, maximum elbow varus torque, and simultaneous kinematic parameters including joint angular acceleration and ball acceleration was investigated. [Results] Peak shoulder internal rotation torque and elbow varus torque averaged 31 Nm and 26 Nm, respectively. Ball acceleration had the strongest influence on shoulder internal rotational torque (standardized partial regression coefficient 0.69). During previous maximum external rotation (pre-MER), the main cause parameter of elbow varus torque was shoulder horizontal adduction velocity (r=0.672). On the other hand, after MER (post-MER), the main cause was ball acceleration (r=0.745). [Conclusion] Results of our study suggest that one of the main mechanical principles of joint load during the baseball pitching motion may be the ‘inertia’ yielded on the segment distal to the certain joint.

Influence of Combinations of Shoulder, Elbow and Trunk Orientation on Elbow Joint Loads in Youth Baseball Pitchers

Objectives:Shoulder and elbow pain in youth baseball pitchers is a well-recognized phenomenon. Common problems in pitching mechanics that can lead to injury begin with stride foot contact. The purpose of this study was to address the relationships between the combinations of shoulder, elbow and trunk orientation at the instant of stride foot contact and elbow joint loads in youth baseball pitchers.Methods:A total of 143 Japanese male youth baseball pitchers participated in this study after providing written informed consents approved by the hospital’s institutional review board. The procedures to be performed were also explained to their parent(s) or legal guardian(s). Each participant was not currently injured or recovering from an injury at time of testing. For data collection of baseball pitching, a set of 14-mm spherical reflective markers was placed on the skin overlying 34 anatomical landmarks determined. Subsequently, a motion capture three-dimensional automatic digitizing system was used to collect 500-Hz from 7 charge-coupled-device synchronized cameras was set up around the regulation pitching mound in an indoor laboratory. After performing a preparation routine of stretching and warm-up pitching, each player pitch to 5 fastball pitches off the pitching mound to a catcher at the regulation distance of 16 m for youth pitchers. The best pitch thrown for a strike was chosen for kinematic and kinetic analysis. The local coordinate systems were used to calculate 3-dimesional rotation at the trunk, shoulder and elbow using the typical Eulerian sequence. Afterward, the standard inverse dynamic equation was used to estimate resultant joint forces and torques at throwing shoulder and elbow. In order to normalize data between subjects, forces and torques were expressed as percent using body weight and height. A multiple regression analysis was carried out to assess the combined effects of shoulder (external rotation, abduction and horizontal adduction), elbow (pronation and extension) and trunk (extension, contralateral tilt, rotation) orientation at SFC and the onset time of trunk rotation on elbow joint loads at SFC. The onset time of trunk rotation was defined as the event in which the magnitude of trunk rotation begins to decrease from tis maximum value.Results:The peak medial force of the elbow was significant correlated with the peak internal rotation torque of the shoulder and the peak varus torque of the elbow (Figure 1). The medial force of the elbow at SFC was significantly correlated with the peak medial force of the elbow (r = .41, p < .001). The adjusted multiple R2 value was 0.45, indicating that over 45% of the variance in the medial force of the elbow at SFC was explained by the regression equation. The standard error of estimate was 4.34. All 3 of the regression variables were significant and are shown in Table 1.Conclusion:The combinations of the greater external rotation of the shoulder, contralateral trunk tilt and elbow extension at SFC may have an indirect influence on the peak medial force on the elbow (Table 1). Then the peak elbow varus torque and shoulder internal rotation torque lead to increase as a result of these. These biomechanical data provide a scientific basis for clinicians, athletes, and coaches to establish methods to prevent pitching-related injuries and improve pitching mechanics.

Associations Between Timing in the Baseball Pitch and Shoulder Kinetics, Elbow Kinetics, and Ball Speed

Background: A baseball pitcher’s ability to maximize ball speed while avoiding shoulder and elbow injuries is an important determinant of a successful career. Pitching injuries are attributed to microtrauma brought about by the repetitive stress of high-magnitude shoulder and elbow kinetics. Hypothesis: Over a number of pitches, variations in timing peak angular velocities of trunk segment rotations will be significantly associated with ball speed and upper extremity kinetic parameters. Study Design: Descriptive laboratory study. Methods: Kinematic and kinetic data were derived from 9 to 15 fastball pitches performed by 16 active, healthy collegiate (n = 8) and professional (n = 8) pitchers via 3-dimensional motion capture (240 Hz). Each pitch was decomposed into 4 phases corresponding to the time between peak angular velocities of sequential body segment rotations. Four mixed models were used to evaluate which phases varied significantly in relation to ball speed, peak shoulder proximal force, peak shoulder internal rotation torque, and peak elbow varus torque. Mixed-model parameter coefficient estimates were used to quantify the influence of these variations in timing on ball speed and upper extremity kinetics. Results: All 4 mixed models were significant (P < .05). The time from stride-foot contact to peak pelvis angular velocity varied significantly in relation to all upper extremity kinetic parameters and ball speed. Increased time in this phase correlated with decreases in all parameters. Decreased ball speed also correlated with increased time between peak upper torso and elbow extension angular velocities. Decreased shoulder proximal force also correlated with increased time between peak pelvis and upper torso angular velocities. Conclusion: There are specific phases that vary in relation to ball speed and upper extremity kinetic parameters, reinforcing the importance of effectively and consistently timing segmental interactions. For the specific interactions that varied significantly, increased phase times were associated with decreased kinetics and ball speed. Clinical Relevance: Although increased time within specific phases correlates with decreases in the magnitude of upper extremity kinetics linked to overuse injuries, it also correlates with decreased ball speed. Based on these findings, it may appear that minimizing the risk of injury (ie, decreased kinetics) and maximizing performance quality (ie, increased ball speed) are incompatible with one another. However, there may be an optimal balance in timing that is effective for satisfying both outcomes.