Maximum Shoulder External Rotation Research Articles

Movement Mechanism Differences of Badminton Overhead Forehand and Backhand Smash Stroke Techniques during Teaching Learning in Human Movement Science

This study aims to analyze the movement of backhand and forehand smash stroke techniques in three dimen- sions using a kinematics approach in badminton. The results were analyzed using a descriptive and quantitative approach. Furthermore, 24 male badminton players from the University Student Activity Unit with an average age of 19.4±1.6 years, a height of 1.73±0.12m, and a weight of 62.8±3.7kg were used. The study was conducted using 3 Panasonic Handycams, a calibration set, 3D Frame DIAZ IV motion analysis software, and a speed radar gun. The data normalization from the kinematics values of the shoulder, elbow, and wrist joint motion was calculated using the inverse dynamics method. Also, the one-way Anova test was used to determine the differences in the kinematics of motion in the two different groups. The results showed that the speed of the shuttlecock during the forehand smash was greater than the backhand. In the maximal shoulder external rotation phase, two variables were found with the best results during the forehand smash, namely the velocity of shoulder external rotation and wrist palmar flexion. The velocity of shoulder internal rotation, elbow extension, and forearm supination in the maximum angu- lar velocity phase showed greater results when making a forehand smash.

The influence of shoulder abduction and external rotation on throwing arm kinetics in professional baseball pitchers.

The relationships between shoulder abduction and external rotation with peak kinetic values at the shoulder and elbow in professional baseball pitchers are not well established. Professional pitchers (n = 322) threw 8-12 fastballs under 3D motion analysis (480 Hz). Pitchers were stratified into quartiles by shoulder abduction and external rotation at distinct timepoints. Regression analyses were performed to quantify associations between shoulder position and kinetics. Shoulder abduction remained relatively consistent throughout the pitch (foot contact-ball release: 85.5 ± 11.1-90.7 ± 8.4°); shoulder external rotation increased dramatically (foot contact-ball release: 30.8 ± 24.6-165.2 ± 9.7°). For every 10° increase in maximum shoulder rotation, shoulder superior force increased by 2.3% body weight (p < 0.01), shoulder distraction force increased by 5.9% body weight (p < 0.01), and ball velocity increased by 0.60 m/s (p < 0.01). Shoulder abduction was significantly associated with shoulder superior force at all timepoints but not with ball velocity (p > 0.05). For every 10° increase in shoulder abduction at ball release, shoulder superior force increased by 3.7% body weight (p < 0.01) and shoulder distraction force increased by 11.7% body weight (p < 0.01). Increased shoulder abduction at ball release and increased maximum shoulder external rotation were associated with greater superior and distraction forces in the shoulder. Pitchers can consider decreasing shoulder abduction at later stages of the pitch to around 80° in order to minimize shoulder superior force, with no impact on ball velocity.

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.

Relationship Between Clinical Scapular Assessment and Scapula Resting Position, Shoulder Strength, and Baseball Pitching Kinematics and Kinetics.

Background:Scapular assessment is important in examining overhead athletes, but there is inconsistency in scapular clinical assessment and its relation to pathology.Purpose:To determine the relationship between clinical scapular assessment and biomechanical scapula resting position, shoulder strength, and pitching shoulder kinematics and kinetics.Study Design:Descriptive laboratory study.Methods:Two clinicians performed scapular assessments and graded the scapula as presence or absence of scapular dyskinesis. Shoulder external rotation (ER) and internal rotation (IR) strength were collected. The 3-dimensional biomechanics of the scapula resting position (upward/downward rotation, IR/ER, and anterior/posterior tilt) were assessed while participants stood at rest, and pitching kinematics (maximum shoulder ER, shoulder abduction, shoulder horizontal abduction, shoulder rotation velocity) and kinetics (maximum shoulder distraction force) were assessed when participants pitched off the portable pitching mound that was engineered to meet major league specifications.Results:A total of 33 high school baseball pitchers (age, 16.3 ± 1.2 years; height, 184.0 ± 6.9 cm; weight, 76.8 ± 20.8 kg; hand dominance: left, 9 [27%]; right, 24 [73%]; pitch velocity, 34.7 ± 2.3 m/s) participated in this study. Of them, 15 participants had scapular dyskinesis, and 18 had normal scapulothoracic rhythm. No differences were observed for upward/downward rotation or anterior/posterior tilt, shoulder ER, shoulder abduction, or shoulder distraction force, based on the presence of scapular dyskinesis. Pitchers with scapular dyskinesis demonstrated significantly greater scapular resting IR position (effect size [ES], 0.80; 95% CI, 0.06 to 1.54; P = .020), greater nondominant shoulder ER to IR strength ratio (ES, 0.49; 95% CI, –0.02 to 1.00; P = .018), and decreased shoulder rotation velocity (ES, 14.66; 95% CI: 12.06 to 17.25; P = .016). Pitchers with greater anterior tilt demonstrated greater shoulder rotation velocity (r = –0.48; P = .006).Conclusion:Pitchers with scapular dyskinesis had greater scapular IR, greater nondominant shoulder ER to IR strength ratio, and reduced shoulder rotation velocity.Clinical Relevance:Scapular assessment may be more influenced by differential IR than upward rotation or anterior tilt. Scapular dyskinesis has no competitive performance advantage among amateur athletes. Greater understanding is needed to decipher the critical threshold between beneficial and maladaptive scapular movement patterns.

The relationship between variability in baseball pitching kinematics and consistency in pitch location

ABSTRACT The purpose of this study was to explore the relationship between variability in pitching kinematics and consistency in pitch location. Data were collected for 47 healthy baseball pitchers throwing ten full-effort fastballs to the centre of the strike zone. For each pitch, 20 kinematic parameters were calculated with an automated motion capture system while pitch location was measured with a PITCHf/x system. Variability of each kinematic parameter was defined for each pitcher as the standard deviation among his fastballs thrown. For calculating consistency, each pitcher’s mean pitch location was first calculated. The distances from each individual pitch to the mean pitch location were then found for each pitcher tested. A consistency metric was then calculated for each pitcher by averaging these distances. A multiple linear regression model was developed using stepwise regression with backwards elimination. The resulting model explained 58% of the variance in the consistency metric and included five parameters, three at foot contact (upper trunk tilt, shoulder abduction, and shoulder horizontal abduction) and two at time of maximum shoulder external rotation (shoulder external rotation and shoulder horizontal adduction). Reducing variability at the shoulder during the early portions of the pitching motion may improve consistency of ball location.

Posterior shoulder tightness can be a risk factor of scapular malposition: a cadaveric biomechanical study

Scapular malposition and posterior shoulder tightness are key pathologic processes in the shoulder of throwing athletes. The objective of this study was to investigate the effects of posterior capsule tightness, posterior rotator cuff muscle tightness, or bothon scapular position. Ten shoulders from 5 fresh frozen cadaveric male torsos were tested in maximum internal, neutral, and maximum external shoulder rotations at 0°, 45°, and 90° of shoulder abduction. Scapular rotation-namely, upward and downward rotation, internal and external rotation, and anterior and posterior tilt-and the scapula-spine distance were measured by using a MicroScribe digitizer (Revware, Raleigh, NC, USA). Each shoulder underwent 4 experimental stages: intact; isolated posterior rotator cuff muscle (infraspinatus and teres minor) tightness; both posterior rotator cuff muscle and capsule tightness; and isolated posterior capsule tightness. Posterior muscle tightness significantly decreased upward rotation (P< .05) only in maximum shoulder internal rotation at 45° or 90° of shoulder abduction, whereas posterior capsule tightness did not affect upward rotation (P= .09 to .96). Posterior capsule tightness significantly increased scapular internal rotation (P< .01), but posterior muscle tightness did not change scapular internal rotation (P= .62 to .89). Posterior capsule tightness significantly increased both the superior and inferior scapula-spine distance (ie, caused scapular protraction) in maximum shoulder external rotation at 90° of abduction (P< .01). Posterior shoulder tightness resulted in scapular malposition. However, the muscular and capsular components of that tightness affected the scapular position differently. For the treatment of scapula malposition, stretching of the posterior shoulder capsule and muscles is recommended.

Effect of different trunk postures on scapular muscle activities and kinematics during shoulder external rotation

Shoulder external rotation at abduction (ER) is a notable motion in overhead sports because it could cause strong stress to the elbow and shoulder joint. However, no study has comprehensively investigated the effect of different trunk postures during ER. This study aimed to investigate the effect of different trunk postures on scapular kinematics and muscle activities during ER. Fourteen healthy men performed active shoulder external rotation at 90° of abduction with the dominant arm in 15 trunk postures. At maximum shoulder external rotation in 15 trunk postures, including 4 flexion-extension, 6 trunk rotation, and 4 trunk side-bending postures, as well as upright posture as a control, scapular muscle activities and kinematics were recorded using surface electromyography and an electromagnetic tracking device, respectively. The data obtained in the flexion-extension, trunk rotation, and trunk side-bending postures were compared with those obtained in the upright posture. In the flexion-extension condition, scapular posterior tilt and external rotation significantly decreased, but the muscle activities of the lower trapezius and infraspinatus significantly increased in maximum trunk flexion. Moreover, scapular upward rotation and the activity of the serratus anterior significantly increased in maximum trunk extension. In the rotation condition, scapular posterior tilt and external rotation significantly decreased, but the activity of the serratus anterior significantly increased in the maximum contralateral trunk rotation posture. In the trunk side-bending condition, scapular posterior tilt and the external rotation angle significantly decreased. Trunk postures affected scapular kinematics and muscle activities during ER. Our results suggestthat different trunk postures activate the lower trapezius and serratus anterior, which induce scapular posterior tilt.

Influence of thoracic posture on scapulothoracic and glenohumeral motions during eccentric shoulder external rotation

BackgroundThrowing injuries to the shoulder joint often occur during shoulder external rotation. An appropriate combination of thoracic, scapular, and humeral motion during throwing is important to prevent such injuries, but it is unclear how thoracic posture contributes to shoulder motion during throwing. Research questionThe purpose of this study, therefore, was to clarify the influence of thoracic posture on scapulothoracic and glenohumeral motion during shoulder external rotation. MethodsEccentric external rotation at 90° of shoulder abduction in thoracic flexion and extension postures was performed by 15 asymptomatic participants. Three-dimensional scapulothoracic and glenohumeral movements were measured with an electromagnetic tracking device at 75°, 80°, 85°, and maximum shoulder external rotation. The thoracic angle and maximum shoulder external rotation in absolute coordination were measured with a three-dimensional motion capture system. ResultsThe results showed that scapular posterior tilting and external rotation in the thoracic extension posture were significantly greater than those in the flexion posture (p < 0.05). Glenohumeral horizontal extension was significantly less in the thoracic extension posture than in the flexion posture (p < 0.05), whereas maximum shoulder external rotation was significantly greater (p < 0.01). Thus, thoracic extension increased scapulothoracic posterior tilting and external rotation and reduced glenohumeral horizontal extension during shoulder external rotation, as well as increasing maximum shoulder external rotation. SignificanceThese findings suggest that thoracic extension may contribute to reduction of mechanical demand in the glenohumeral joint during throwing, potentially reducing shoulder injuries.

Closed Treatment of Shoulder Dislocation in Children With Birth Brachial Plexus Injuries

There is no financial information to disclose. With earlier recognition of shoulder dysplasia, is there a role for intervention with closed shoulder reduction and botulinum toxin injections to improve shoulder dysplasia or prevent future open procedures? Early ultrasound identification and closed treatment of glenohumeral dysplasia in patients with birth brachial plexus injuries (BBPI) and shoulder subluxation can prevent worsening deformity and decrease the need for open shoulder reduction. 26 consecutive patients with BBPI who underwent closed shoulder reductions with or without botulinum toxin injections at a mean age of 6.5 months (range 3–19 months) were followed to failure of treatment (n = 18) or to an average follow-up of 40 months (range 12–66 months). All children included in the study were identified clinically by loss of passive external rotation (PER) with imaging confirming shoulder dislocation (Figure 23-1). All children were treated with closed reduction of the glenohumeral joint under general anesthesia and were casted in maximum shoulder external rotation (ER) (Figure 23-2). Treatment outcomes were assessed by changes in ER and ultrasound measurements of humeral head coverage (HHC) and alpha angle. Descriptive and comparative statistics were performed for all patients with available follow-up for preoperative versus postoperative AMS shoulder ER, PER, ultrasound percent HHC, and alpha angle for initial postoperative values (average 11 weeks). For patients undergoing open reduction, subgroup analysis was performed. Final outcome measures for patients not requiring subsequent open reduction were compared with preoperative measures for AMS and shoulder position. Active Movement Scale shoulder external rotation score improved by 0.7 posttreatment. Passive external rotation increased by 42° (P < .001). Humeral head coverage improved by 39% (P < .001). Alpha angle improved by –41° (P < .001). 18 patients (69%) required an open reduction and tendon transfer of the affected shoulder at an average of 13.4 months (range 1–47 months) after the index procedure. 7 patients (27%) did not require further open shoulder reduction. Of these 7 patients, 2 needed repeated botulinum toxin injections, and 1 repeated closed reduction and nerve transfer. 1 patient was lost to follow -up. The age at the time of closed shoulder reduction was significantly lower in the 7 children who did not require subsequent open reduction. •Early closed reduction of shoulder dislocation in patients with birth brachial plexus injuries improves PER, HHC, and alpha angle.•Early detection and closed treatment can prevent subsequent open reduction in 27% of children.•The authors recommend ultrasound screening of all children with BBPI and loss of PER.Figure 23-2All patients were immobilized for 4–6 weeks with the arm in 30° abduction and maximum external rotation with intraoperative ultrasound confirmation of shoulder reduction.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Relationship of Glove Arm Kinematics With Established Pitching Kinematic and Kinetic Variables Among Youth Baseball Pitchers.

Background:While the kinematics of the pitching arm, trunk, and pelvis have been described and studied, glove arm kinematics remain an understudied portion of the pitching motion. Baseball pitchers seek to achieve maximum ball velocity in a fashion that does not place the arm at risk of injury.Purpose:To assess the relationship between glove arm shoulder horizontal abduction and elbow flexion and pitching arm kinematics and kinetics among youth pitchers to determine whether recommendations can be made toward a safer pitching motion.Study Design:Descriptive laboratory study.Methods:Thirty-three right-handed youth male baseball pitchers (mean ± SD: age, 13.6 ± 2.0 years; height, 169.4 ± 14.3 cm; weight, 63.5 ± 13.0 kg; experience, 7.3 ± 3.0 years) threw 3 fastballs to a catcher while kinematic data were collected with an electromagnetic tracking system. The Spearman rank-order test was used to identify relationships between glove arm horizontal abduction and glove arm elbow flexion and various kinematics and kinetics found at maximum shoulder external rotation (MER) and ball release for the fastest fastball delivered by each participant.Results:At MER, there were significant relationships found between a more flexed glove arm elbow and increased pitching arm elbow valgus force (rs[31] = –0.52, P = .002), increased pitching arm shoulder anterior force (rs = –0.39, P = .024), and decreased hip velocity (rs[31] = –0.45, P = .009). Additionally, there were significant relationships between greater glove arm horizontal abduction at MER and increased pitching arm humeral velocity (rs[31] = 0.52, P = .002) and increased trunk rotational velocity (rs[31] = 0.40, P = .022) at MER.Conclusion:A more extended glove arm elbow and more horizontally abducted glove arm shoulder at MER could prove to be more advantageous for performance and possibly be a safer motion for the baseball thrower.Clinical Relevance:The orthopaedic community can dictate safer biomechanics when communicating with pitchers, trainers, and pitching coaches.

Effects of Game Pitch Count and Body Mass Index on Pitching Biomechanics in 9- to 10-Year-Old Baseball Athletes.

Background:Pitching while fatigued and body composition may increase the injury risk in youth and adult pitchers. However, the relationships between game pitch count, biomechanics, and body composition have not been reported for a study group restricted to 9- to 10-year-old athletes.Hypothesis:During a simulated game with 9- to 10-year-old athletes, (1) participants will experience biomechanical signs of fatigue, and (2) shoulder and elbow kinetics will correlate with body mass index (BMI).Study Design:Descriptive laboratory study.Methods:Thirteen 9- to 10-year-old youth baseball players pitched a simulated game (75 pitches). Range of motion and muscular output tests were conducted before and after the simulated game to quantify fatigue. Kinematic parameters at foot contact, maximum external rotation, and maximum internal rotation velocity (MIRV), as well as maximum shoulder and elbow kinetics between foot contact and MIRV were compared at pitches 1-5, 34-38, and 71-75. Multivariate analyses of variance were used to test the first hypothesis, and linear regressions were used to test the second hypothesis.Results:MIRV increased from pitches 1-5 to 71-75 (P = .007), and head flexion at MIRV decreased from pitches 1-5 to 34-38 (P = .022). Maximum shoulder horizontal adduction, external rotation, and internal rotation torques increased from pitches 34-38 to 71-75 (P = .031, .023, and .021, respectively). Shoulder compression force increased from pitches 1-5 to 71-75 (P = .011). Correlations of joint torque/force with BMI were found at every pitch period: for example, shoulder internal rotation (R 2 = 0.93, P < .001) and elbow varus (R 2 = 0.57, P = .003) torques at pitches 1-5.Conclusion:Several results differed from those of previous studies with adult pitchers: (1) pitch speed remained steady, (2) shoulder MIRV increased, and (3) shoulder kinetics increased during a simulated game. The strong correlations between joint kinetics and BMI reinforce previous findings that select body composition measures may be correlated with pitching arm joint kinetics for youth baseball pitchers.Clinical Relevance:The results improve our understanding of pitching biomechanics for 9- to 10-year-old baseball pitchers and may be used in future studies to improve evidence-based injury prevention guidelines.

Kinematic and kinetic differences between left-and right-handed professional baseball pitchers

While 10% of the general population is left-handed, 27% of professional baseball pitchers are left-handed. Biomechanical differences between left- and right-handed college pitchers have been previously reported, but these differences have yet to be examined at the professional level. Therefore, the purpose of this study was to compare pitching biomechanics between left- and right-handed professional pitchers. It was hypothesised that there would be significant kinematic and kinetic differences between these two groups. Pitching biomechanics were collected on 96 left-handed pitchers and a group of 96 right-handed pitchers matched for age, height, mass and ball velocity. Student t-tests were used to identify kinematic and kinetic differences (p < 0.05). Of the 31 variables tested, only four were found to be significantly different between the groups. Landing position of the stride foot, trunk separation at foot contact, maximum shoulder external rotation and trunk forward tilt at ball release were all significantly greater in right-handed pitchers. The magnitude of the statistical differences found were small and not consistent with differences in the two previous, smaller studies. Thus, the differences found may be of minimal practical significance and mechanics can be taught the same to all pitchers, regardless of throwing hand.

Role of Rotational Kinematics in Minimizing Elbow Varus Torques for Professional Versus High School Pitchers.

Background:Elbow injury rates among baseball pitchers are rapidly rising. However, this increase has been most dramatic among high school (HS) pitchers.Purpose:To examine pitch velocity and the kinetic and kinematic characteristics of HS versus professional (PRO) pitchers to identify potential differences that may play a role in the increased risk of ulnar collateral ligament injury in youth pitchers.Study Design:Controlled laboratory study.Methods:A total of 37 HS (mean ± SD: age, 16 ± 1 years) and 40 PRO (age, 21 ± 2 years) baseball pitchers completed maximal-effort baseball pitches during a single testing session, from which pitch velocity (PV), absolute and normalized elbow varus torque (EVTA and EVTN, respectively) during arm cocking and at maximum shoulder external rotation (MER), and 8 other elbow and shoulder torques or forces and rotational kinematics of the pelvis and trunk were analyzed, recorded, and compared.Results:PV was greater in PRO than HS athletes; EVTA was greater in PRO than HS athletes during arm cocking and at MER; but EVTN was similar during arm cocking and greater in HS than PRO athletes at MER. In PRO athletes, PV was not related to EVTA during arm cocking or MER (r = 0.01-0.05). Furthermore, in PRO athletes, EVTA during arm cocking and at MER were inversely related to upper trunk rotation at hand separation and foot contact and to pelvis rotation at elbow extension (r = –0.30 to –0.33). In contrast, in HS athletes, PV was strongly related to EVTA during arm cocking and MER (r = 0.76-0.77). Furthermore, in HS athletes, PV and EVTA during arm cocking and at MER were moderately or strongly related to the other elbow and shoulder torques and forces (r = 0.424-0.991), and EVTA was not related to upper trunk rotation or pelvis rotation throughout the throwing motion (r = –0.16 to 0.15).Conclusion:The kinetic and rotational kinematic differences observed between PRO and HS pitchers in this study may help explain the greater performance of PRO pitchers while allowing them to minimize EVT during pitching. HS pitchers, however, do not appear to be as capable of utilizing the forces generated by rotation of their trunk and pelvis to aid in pitching, and those who throw the hardest generate the greatest forces at the shoulder and elbow. As a result, they experience higher EVTs relative to their body size, which may place them at an increased risk of injury.Clinical Relevance:HS pitchers throw harder primarily by generating larger forces in the arm and shoulder. Thus, owing to the relative physical immaturity of HS versus PRO pitchers, these factors may place them at an increased risk of injury. Coaches may first wish to focus on improving the rotational kinematics of HS pitchers rather than first focusing on achieving greater pitch velocities.

TRUNK LEAN DURING A SINGLE-LEG SQUAT IS ASSOCIATED WITH TRUNK LEAN DURING PITCHING

Impaired trunk motion during pitching may be a risk factor for upper extremity injuries. Specifically, increased forces about the shoulder and elbow have been observed in pitchers with excessive contralateral trunk lean during pitching. Because of the difficulty in identifying abnormal trunk motions during a high-speed task such as pitching, a clinical screening test is needed to identify pitchers who have impaired trunk motion during pitching. The purpose of this study was to determine the relationship between the degree of lateral trunk lean during the single-leg squat and amount of trunk lean during pitching and if trunk lean during pitching can be predicted from lean during the single-leg squat. Controlled Laboratory Study; Cross-sectional. Seventy-three young baseball pitchers (11.4 ± 1.7 years; 156.3 ± 11.9 cm; 50.5 ± 8.8 kg) participated. An electromagnetic tracking system was used to obtain trunk kinematic data during a single-leg squat task (lead leg) and at maximum shoulder external rotation of a fastball pitch. Pearson correlation coefficients for trunk lean during the single-leg squat and pitching were calculated. A linear regression analysis was performed to determine if trunk lean during pitching can be predicted from lean during the single-leg squat. There was a positive correlation between trunk lean during the single-leg squat and trunk lean during pitching (r = 0.53; p<0.001). Lateral trunk lean during the single-leg squat predicted the amount of lateral trunk lean during pitching (R2 = 0.28; p < 0.001). A moderate positive correlation was observed between trunk lean during an SLS and pitching. Trunk lean during the single-leg squat explained 28% of the variance in trunk lean during pitching. Diagnosis, level 3.

Classification of lumbopelvic-hip complex instability on kinematics amongst female team handball athletes

ObjectivesThe purpose of this study was to examine how lumbopelvic-hip complex (LPHC) stability, via knee valgus, affects throwing kinematics during a team handball jump shot. DesignLPHC stability was classified using the value of knee valgus at the instant of landing from the jump shot. If a participant displayed knee valgus of 17° or greater, they were classified as LPHC unstable. Stable and unstable athletes’ throwing mechanics were compared. MethodsTwenty female team handball athletes (26.5±4.7years; 1.75±0.04m; 74.4±6.4kg; experience level: 4.8±4.1 years) participated. An electromagnetic tracking system was used to collect kinematic data while participants performed three 9-m jump shots. The variables considered were kinematics of the pelvis, trunk, and shoulder; and segmental speeds of the pelvis, torso, humeral, forearm, and ball velocities. Data were analyzed across four events: foot contact, maximum shoulder external rotation, ball release, and maximum shoulder internal rotation. ResultsStatistically significant differences were found between groups in pelvis, trunk, humerus, and forearm velocities at all events (p≤0.05). Specifically, the unstable group displayed significantly slower speeds. ConclusionsThese findings suggest the difference in throwing mechanics are affected by LPHC instability for this select group of female team handball athletes. These differences infer an increased risk of injury in the upper and lower extremities when landing from a jump shot because of the energy losses throughout the kinetic chain and lack of utilization of the entire chain. It is recommended that further investigations also consider muscle activation throughout the throwing motion.

Three-dimensional kinematic analysis of glenohumeral, scapular, and thoracic angles at maximum shoulder external rotation associated with baseball shadow pitching: comparison with normal pitching

[Purpose] The glenohumeral, scapular, and thoracic angles at maximum shoulder external rotation during shadow pitching were evaluated and compared with those observed during normal pitching. [Participants and Methods] Our study included 13 healthy males with experience in pitcher activity. All participants performed both, shadow pitching using a towel and normal pitching using a ball. The external rotation of the glenohumeral joint, scapular posterior tilting, and thoracic extension angles in the cocking phase were measured using a 3-dimensional motion analysis system. The ratios of the glenohumeral external rotation angle to the scapular posterior tilting and/or thoracic extension angle were calculated to evaluate the contribution of the scapulothoracic joint at maximum external rotation during throwing/pitching activity. [Results] The glenohumeral external rotation angle at maximum shoulder external rotation was significantly smaller during shadow pitching than during normal pitching. The ratio of the glenohumeral external rotation angle to the scapular posterior tilting and/or thoracic extension angle showed no statistically significant difference. [Conclusion] We conclude that shadow pitching can reduce the external rotation motion of the glenohumeral joint compared to that during normal pitching and might be a useful pre-throwing program beneficial in the rehabilitation of those presenting with throwing injuries.

Youth Baseball Pitching Mechanics: A Systematic Review.

Context:Pitching injuries in youth baseball are increasing in incidence. Poor pitching mechanics in young throwers have not been sufficiently evaluated due to the lack of a basic biomechanical understanding of the “normal” youth pitching motion.Objective:To provide a greater understanding of the kinetics and kinematics of the youth baseball pitching motion.Data Sources:PubMed, MEDLINE, and SPORTDiscus databases were searched from database inception through February 2017.Study Selection:A total of 10 biomechanical studies describing youth pitching mechanics were included.Study Design:Systematic review.Level of Evidence:Level 3.Data Extraction:Manual extraction and compilation of demographic, methodology, kinetic, and kinematic variables from the included studies were completed.Results:In studies of healthy youth baseball pitchers, progressive external rotation of the shoulder occurs throughout the start of the pitching motion, reaching a maximum of 166° to 178.2°, before internally rotating throughout the remainder of the cycle, reaching a minimum of 13.2° to 17°. Elbow valgus torque reaches the highest level (18 ± 4 N·m) just prior to maximum shoulder external rotation and decreases throughout the remainder of the pitch cycle. Stride length is 66% to 85% of pitcher height. In comparison with a fastball, a curveball demonstrates less elbow varus torque (31.6 ± 15.3 vs 34.8 ± 15.4 N·m).Conclusion:Multiple studies show that maximum elbow valgus torque occurs just prior to maximum shoulder external rotation. Forces on the elbow and shoulder are greater for the fastball than the curveball.

Biomechanical Comparisons Among Fastball, Slider, Curveball, and Changeup Pitch Types and Between Balls and Strikes in Professional Baseball Pitchers

Background: In professional baseball pitchers, pitching biomechanics have not been examined for the slider, and the only known study for the curveball and changeup examined limited kinetics. Moreover, no known studies have investigated pitching biomechanics between strikes and balls. Purpose/Hypothesis: The purpose was to compare pitching biomechanics in professional baseball pitchers among the fastball, slider, curveball, and changeup and between balls and strikes. It was hypothesized that pitching kinematics and kinetics would be similar among the slider, fastball, and curveball; shoulder and elbow forces and torques would be significantly lower in the changeup; and pitching biomechanics would be similar between balls and strikes. Study Design: Controlled laboratory study. Methods: Among 18 professional baseball pitchers, 38 reflective markers were positioned on the body and each player threw 32 to 40 maximum effort pitches—consisting of the fastball, curveball, slider, and changeup pitch types—from a regulation mound to a catcher. The markers were tracked by 18 high-speed 180-Hz cameras, and data were processed and run through a computer program to calculate 25 kinematic parameters, 7 kinetic parameters, and 4 temporal parameters for each pitch type and for both strikes and balls. A 2-way repeated-measures analysis of variance (P < .01) was used to assess pitching biomechanical differences among pitch type and pitch result (balls vs strikes). Results: During arm cocking, elbow varus torque was 8% to 9% greater in the fastball and slider compared with the changeup, shoulder horizontal adduction torque was 17% to 20% greater in the slider and curveball compared with the changeup, and shoulder anterior force was 13% greater in the curveball compared with the changeup. During arm deceleration, elbow flexor torque was 9% to 14% greater in the fastball compared with the curveball and changeup, and elbow and shoulder proximal forces were 10% to 14% greater in the fastball, slider, and curveball compared with the changeup. At ball release, forward trunk tilt was 16% to 19% greater in the fastball and curveball compared with the changeup, contralateral trunk tilt was 26% to 41% greater in the curveball compared with the slider and changeup, knee flexion was 18% greater in the changeup compared with the fastball, and the knee extended 7° more from lead foot contact to ball release in the fastball compared with the changeup. During arm cocking, pelvis angular velocity was 7% to 8% greater in the fastball compared with the curveball and changeup, and upper trunk angular velocity was 5% greater in the fastball compared with the changeup. During arm acceleration, shoulder internal rotation angular velocity was 6% to 7% greater in the fastball, slider, and curveball compared with the changeup, and ball velocity at ball release was 11% to 18% greater in the fastball compared with the slider, changeup, and curveball and 6% greater in the slider compared with the curveball. For all the kinematic, kinetic, and temporal parameters, analysis showed no significant differences between balls and strikes and no significant interactions between pitch type and pitch result. Conclusion: Nearly all kinetic differences among pitch types occurred between the changeup and the remaining 3 pitch types. Shoulder and elbow forces and torques and injury risk were greater among the fastball, slider, and curveball compared with the changeup but were similar among the fastball, slider, and curveball. Body segment and joint positions were similar among all pitch types at lead foot contact and at maximum shoulder external rotation; however, at ball release, throwing a fastball and curveball resulted in greater knee extension and more forward and contralateral trunk tilt compared with throwing a changeup and slider. Movement speeds for the pelvis, upper trunk, and shoulder were greatest in the fastball and least in the changeup and were generally similar among the fastball, slider, and curveball. The timing of when pelvis, upper trunk, elbow, and shoulder velocities occurred among the fastball, slider, curveball, and changeup was similar, and no kinematic or kinetic differences were noted between throwing balls and strikes. Clinical Relevance: The results from the current study will help clinicians understand differences in pitching biomechanics in professional baseball pitchers among the fastball, slider, curveball, and changeup; the study provides limited insight into shoulder and elbow injury risk associated with different types of pitches.

Changes in Youth Baseball Pitching Biomechanics: A 7-Year Longitudinal Study

Background: Pitching biomechanics are associated with performance and risk of injury in baseball. Previous studies have identified biomechanical differences between youth and adult pitchers but have not investigated changes within individual young pitchers as they mature. Hypothesis: Pitching kinematics and kinetics will change significantly during a youth pitcher’s career. Study Design: Descriptive laboratory study. Methods: Pitching biomechanics were captured in an indoor laboratory with a 12-camera, 240-Hz motion analysis system for 51 youth pitchers who were in their first season of organized baseball with pitching. Each participant was retested annually for the next 6 years or until he was no longer pitching. Thirty kinematic and kinetic parameters were computed and averaged for 10 fastballs thrown by each player. Data were statistically analyzed for the 35 participants who were tested at least 3 times. Within-participant changes for each kinematic and kinetic parameter were tested by use of a mixed linear model with random effects (P < .05). Least squares means for sequential ages were compared via Tukey’s honestly significant difference test (P < .05). Results: Three kinematic parameters that occur at the instant of foot contact—stride length, lead foot placement to the closed side, and trunk separation—increased with age. With age, shoulder external rotation at foot contact decreased while maximum shoulder external rotation increased. Shoulder and elbow forces and torques increased significantly with age. Year-to-year changes were most significant between 9 and 13 years of age for kinematics and between 13 and 15 years for normalized kinetics (ie, scaled by bodyweight and height). Conclusion: During their first few years, youth pitchers improve their kinematics. Elbow and shoulder kinetics increase with time, particularly after age 13. Thus, prepubescent pitchers may work with their coaches to improve the motions and flexibility of the players’ bodies and the paths of their arms. Once proper mechanics are developed, adolescent pitchers can focus more on improving strength and power.

Reliability, Responsiveness, and Criterion Validity of the Kiio Sensor, a New Tool for Assessment of Muscle Function.

Musculoskeletal injuries are a leading cause of disability in both the general population and military, and the ability to effectively quantify musculoskeletal function remains problematic. The aim of the current study is to investigate the reliability, responsiveness, and criterion validity of the kiio Sensor for measurement of muscle strength, a key aspect of comprehensive functional assessment. Forty-four (24 male, 20 female) physically active civilian adults (mean [SD] = 21.2 [1.5] years of age) with no history of upper extremity injuries in the last year and no current complaints of pain, weakness, or functional limitation completed two sessions of maximum shoulder external rotation contractions. The forces were measured with a kiio Sensor and isokinetic dynamometer. The devices showed strong correlation (r = 0.89) and no significant mean difference (0.3 ± 3.3 lb, p = 0.47). Intrasession reliability for both devices was analyzed using intraclass correlation coefficients (ICC3,1 = 0.96 [95% confidence interval = 0.93-0.98)], with the kiio Sensor having slightly less standard error and trial-to-trial variability. The kiio Sensor 7-day reliability was ICC3,3 = 0.97 (95% confidence interval = 0.94-0.98). The kiio Sensor demonstrates excellent reliability, responsiveness, and validity compared with a gold standard isokinetic dynamometer. Several key attributes contributing to this technology's military relevance are discussed.