Peak Elbow Research Articles

Stride-Phase Kinematic Parameters That Predict Peak Elbow Varus Torque.

Background:During baseball pitching, a high amount of elbow varus torque in the arm cocking-to-acceleration phase is thought to be a biomechanical risk factor for medial elbow pain and injury. The biomechanics of the stride phase may provide preparation for the arm cocking-to-acceleration phase that follows it.Purpose:To determine the kinematic parameters that predict peak elbow varus torque during the stride phase of pitching.Study Design:Descriptive laboratory study.Methods:Participants were 107 high school baseball pitchers (age range, 15-18 years) without shoulder or elbow problems. Whole-body kinematics and kinetics during fastball pitching were analyzed using 3-dimensional measurements from 36 retroreflective markers. A total of 26 kinematic parameters of the upper and lower limbs during the stride phase leading up to the stride foot contact were extracted for multiple regression analysis to assess their combined effect on the magnitude of peak elbow varus torque.Results:Increased wrist extension, elbow pronation, knee flexion on the leading leg, knee extension on the trailing leg at stride foot contact, and upward displacement of the body’s center of mass in the stride phase were significantly correlated with decreased peak elbow varus torque (all P < .05). Moreover, 38% of the variance in peak elbow varus torque was explained by a combination of these 5 significant kinematic variables (P < .001).Conclusion:We found that 5 kinematic parameters during the stride phase and the combination of these parameters were associated with peak elbow varus torque. The stride phase provides biomechanical preparation for pitching and plays a key role in peak elbow varus torque in subsequent pitching phases.Clinical Relevance:The present data can be used to screen pitching mechanics with motion capture assessment to reduce peak elbow varus torque. Decreased peak elbow varus torque is expected to reduce the risk of elbow medial pain and injury.

Anatomic Restoration of the Biceps Brachii Insertion Through a Single Anterior Incision.

Treatment of distal biceps tendon ruptures with surgical repair has been shown to restore peak elbow flexion and supination strength, as well as minimize fatigue with repetitive activity. The anatomic footprint of the biceps is slightly posterior to the apical prominence of the bicipital tuberosity. Single-incision and double-incision methods for repairing distal biceps tendon ruptures have been described. However, previously described single-incision techniques have been unable to accurately re-establish the anatomic position of the tendinous insertion. We describe our technique of performing an anatomic distal biceps repair using a single anterior incision. The proposed benefits of this technique include the restoration of the anatomic footprint area, insertion site, and consequently the native cam effect of the bicipital tuberosity all through a single incision. From a patient's perspective, the proposed benefit of this technique includes the restoration of supination strength using a single incision.

The Kinematic Sequence Of The Baseball Bat Swing And Associated Upper Extremity Torques

PURPOSE: The Kinematic Sequence (KS) is the timing of peak angular velocities generated across connected body segments during a movement pattern. The most efficient KS reported in sport is when the timing occurs in a proximal-to-distal (PDS) pattern. This ‘ideal’ KS follows the order of pelvis, trunk, arm, forearm, and hand. Based on simulated models of the golf swing, the PDS KS results in greater ball distance and decreased joint stresses. Despite similarities to the golf swing, there is limited research on the KS during batting. Study aims: 1) Identify KSs during the baseball swing and 2) compare the leading upper extremity torques across the 3 primary KSs. METHODS: 23 baseball players (professional=2, collegiate=11, high school=10) underwent 3D biomechanical swing analysis, totaling 47 trials. A 15-segment model was constructed using a 20 Vicon™ camera motion capture system (240 hz). Body segment and bat velocities as well as peak shoulder and elbow torques were calculated using Visual 3D™ biomechanical software. Time of peak angular velocity of the pelvis, trunk, arm, forearm, and hand was recorded. The torques were compared across the two most performed KS patterns as well as the KS representing the closest to a PDS pattern. The KS patterns were labeled by the first body segment that disrupted the PDS pattern: proximal (PUE) and distal (DUE) upper extremity. Analyses included an ANCOVA using bat velocity as a covariant. RESULTS: 11 unique KS patterns were identified. The most commonly performed KSs were DUE (n=23) then PUE (n=13). No batter displayed the exact PDS KS. Therefore, 5 trials that most closely represent the PDS, those with forearm and hand velocities peaking simultaneously, were grouped as PDS. Peak elbow extension torque differed significantly between the 3 KS groups (F(2,37)=4.95, η2=0.21, p=0.012) with lower values for PDS (PDS: 17.94 ± 12.83 Nm, PUE: 51.09 ± 25.19 Nm, DUE: 43.01 ± 22.26 Nm, p=0.012). CONCLUSIONS: This foundational study is the first to apply a KS classification system to the baseball swing. Lower elbow extension torques for the PDS group are consistent with the idea that a PDS KS may result in decreased joint stress. KS analyses could potentially guide clinicians and hitting instruction to minimize biomechanical risk factors during batting.

Upper limb kinematics during the first year after stroke: the stroke arm longitudinal study at the University of Gothenburg (SALGOT)

BackgroundReduction of compensation and improved movement quality indicate recovery after stroke. Since clinical measures alone are often inadequate to distinguish between behavioral recovery and compensation, kinematic analysis of functional tasks has been recommended.ObjectiveTo quantify longitudinal changes and residual deficits in movement performance and quality during the first year after stroke using kinematic analysis of drinking task.MethodsA total of 56 participants with first ever stroke causing upper extremity impairment were extracted from a non-selected stroke unit cohort (Stroke Arm Longitudinal Study at the University of Gothenburg-SALGOT). Participants needed to able to perform the drinking task with the more-affected arm at least on 2 occasions out of 6 (3 days, 10 days, 4 weeks, and 3, 6, and 12 months) during the first year to be included. A cohort of 60 healthy individuals was used as reference. Longitudinal changes were analyzed using linear mixed models.ResultsMovement time, number of movement units, peak angular velocity of the elbow, peak hand velocity, and trunk displacement improved significantly over the first 3 months with a peak at 6 months. Movement time and peak hand velocity reached levels comparable to healthy at 3 months, but number of movement units, peak elbow angular velocity, trunk displacement, and arm abduction remained different from healthy over the first year after stroke.ConclusionsEven when the recovery patterns of kinematics follow the known nonlinear pattern, not all kinematic measures reach the levels in par with healthy controls at one year post stroke. Since the number of movement units, peak angular velocity, trunk displacement, and arm abduction remained impaired over the first year, they might be the most suited measures to distinguish behavioral recovery from compensation strategies.Trial registrationClinicalTrials: NCT01115348. 4 May 2010. Retrospectively registered.

Assessment of throwing arm biomechanics with a motusBASEBALLTM pitching sleeve during long-toss throws and pitching in college baseball pitchers

In baseball, long-toss throws are commonly used in return-to-throw programs and for general conditioning; however, the majority of these programs are based on conventional wisdom. Few studies have examined the biomechanics of long-toss throwing and the impact of throw distance. The purpose of this study was to determine if significant differences exist among commonly-used sub-maximal distance long-toss throws and mound pitching. Nineteen college baseball pitchers (19 ± 1.3 years; 88.3 ± 8.4 kg; and 73.9 ± 18.6 cm) wore a motusBASEBALL™ sleeve and sensor which measured peak elbow varus torque (VT), peak forearm angular velocity (Vmax), and peak arm-cocking angle (ACA). Each player completed five long-toss throws at distances of 27 m, 37 m, 46 m, 55 m and five pitches from a mound at regulation (18.4 m). There were no significant differences among throwing conditions for both VT and Vmax (p&lt;0.05). For ACA, there was a significant increase (approximately 12°) as the long-toss distance increased. Coaches and trainers should be aware that sub-maximal distance long-toss throws (27 - 55 m+) generate high-magnitude throwing arm biomechanics (kinetics, velocities, range of motion) that approach or even exceed those generated during pitching; precaution needs to be used when implementing long-tosses into throwing and rehabilitation programs.

Postural and muscular adaptations to repetitive simulated work

Complex repetitive tasks are common in the workplace and have been associated with upper extremity disorders. The purpose of this study was to examine the progressive effects of highly repetitive work on joint kinematics and muscle activity of the trunk and upper extremity. Fifteen healthy men performed 60 one-minute cycles of 4 simulated automotive-related tasks. Electromyography of eight muscles and kinematics of the trunk and right upper extremity were collected. Data were analysed at 12-min intervals and divided into a complete work cycle. The time to complete the work cycle decreased by 6.3 s over the trials. Peak shoulder flexion decreased and peak elbow flexion increased during the work cycle. Muscle activity magnitude and variability was influenced by time during the repetitive tasks. This study found adaptations to highly repetitive but light work in only 1 h; redistributing muscle demands within the shoulder over time may reduce muscle fatigue development.Practitioner Summary: While the work was not strenuous, we were able to demonstrate muscular and postural adaptations in a single hour of simulated work. By evaluating both the whole work cycle and the sub-tasks, we aim to develop new methods for evaluating the risk of complex tasks in prolonged repetitive work.

Elbow Kinematics During Gait Improve With Age in Children With Hemiplegic Cerebral Palsy.

Children with hemiplegic cerebral palsy (hCP) exhibit a typical posture of elbow flexion during gait. However, the change in elbow kinematics and symmetry during gait across age span in both hCP and typically developing (TD) children is not well described. The aim of this study was to quantify the change in elbow kinematics and symmetry across age span in hCP children compared with TD children. Upper extremity kinematic data were extracted and analyzed from a database for gait studies performed between 2009 and 2015. A total of 35 hCP and 51 TD children between the ages of 4 and 18 (mean age: TD=11.2±0.6, hCP=9.8±0.5) met inclusionary criteria. The groups were further subdivided into 3 age categories: 4 to 7, 8 to 11, 12+ years old. Elbow angles were extracted and peak elbow flexion, overall range of motion during gait, and asymmetry indices were calculated. A 1-way analysis of variance was performed on each group with post hoc Tukey honestly significant difference pairwise comparisons. Peak elbow flexion during gait increased with age in TD children (P<0.05) and decreased with age in hCP children on the affected side (P<0.05). There was no change on the less affected side of hCP children. TD children demonstrated significantly less elbow flexion (mean=51.9±2.1 deg.) compared with the affected side in hCP (mean=82.1±3.8 deg.) across all age categories (P<0.05). There was no change in elbow asymmetry index (0=perfect symmetry) across age in either controls or hCP children; however, there were differences between hCP and TD groups in younger age groups (TD=28, hCP=62, P<0.05) that resolved by adolescence (TD=32, hCP=40). During gait, hCP children have greater peak elbow flexion on the affected side than do TD children. Peak elbow flexion angle converged between the 2 groups with age, decreasing in hCP children and increasing in TD children. Furthermore, elbow symmetry during gait improves with age in hCP children, approximating symmetry of TD children by adolescence. These findings have implications for both consideration and optimal timing of surgical intervention to improve elbow flexion in children with hCP. Level III-retrospective case-control study.

Recovery of kinematic arm function in well-performing people with subacute stroke: a longitudinal cohort study

BackgroundMost motor function improvements in people who have experienced strokes occur within the first 3 months. However, individuals showing complete or nearly complete arm function recovery, as assessed using clinical scales, still show certain movement kinematic deficits at 3 months, post-stroke. This study evaluated the changes in upper extremity kinematics, in individuals demonstrating minor clinical motor impairments, 3–12 months post-stroke, and also examined the association between kinematics and the subjects’s self-perceived hand abilities during the chronic stage, 12 months post-stroke.MethodsForty-two subjects recovering from strokes and having Fugl-Meyer upper extremity motor assessment scores ≥60 were included from the Stroke Arm Longitudinal Study at the University of Gothenburg (SALGOT). Kinematic analyses of a drinking task, performed 3, 6, and 12 months post-stroke, were compared with kinematic analyses performed in 35 healthy controls. The Stroke Impact Scale-Hand domain was evaluated at the 12-month follow-up.ResultsThere were no significant changes in kinematic performance between 3 and 12 months, post-stroke. The patients recovering from stroke showed lower peak elbow extension velocities, and increased shoulder abduction and trunk displacement during drinking than did healthy controls, at all time points. At 12 months, post-stroke, better self-perceived arm functions correlated with improved trunk displacements, movement times, movement units, and time to peak velocity percentages.ConclusionKinematic movement deficits, observed at 3 months post-stroke, remained unchanged at 12 months. Movement kinematics were associated with the patient’s self-perceived ability to use their more affected hand.Trial registrationClinicalTrials: NCT01115348.

The effectiveness of bench press training with or without throws on strength and shot put distance of competitive university athletes.

Maximum force exertion against various resistance levels (heavy-light) is commonly implemented to improve both strength- and speed-oriented components of power. Medium-light resistances allow rapid accelerations, yet incur significant decelerations in the later concentric phase to bring the bar to a halt, which may limit the concentric effort and, therefore, the effectiveness of training. Accordingly, ballistic actions have been recommended. This study evaluated the effectiveness of power bench press training, with the bar thrown on a Smith machine (BPthrow) or without throwing (BPnon-throw), for developing strength and shot put distance. Nine university shot-putters performed BPthrow and BPnon-throw at 50, 40 and 30% 1RM, as well as seated and standing shot put trials. Peak angular velocities at the elbow were measured in these tasks using a wireless electro-goniometer. Participants underwent 24 sessions of training (12weeks) with either BPthrow (n = 5) or BPnon-throw (n = 4) at the three intensities (20s × 2 sets at 50, 40 and 30% 1RM). The peak elbow velocity during BPthrow was 1.7 times greater than BPnon-throw for all intensities. The velocity of BPthrow at 30% 1RM (854.7°/s), however, was still slower than seated (1121.3°/s) and standing (1539.1°/s) shot puts. BPthrow training significantly improved 1RM (+ 10.0%) and the distances of seated (+ 11.7%) and standing (+ 3.8%) shot puts, while no performance changes occurred after BPnon-throw training. When undergoing power bench press against medium-light resistances, maximum ballistic actions are important strategies for improving 1RM and shot put performance of university shot-putters.

Technique selection in young female gymnasts: Elbow and wrist joint loading during the cartwheel and round-off

Biophysical loading of the elbow and wrist is a potential reason for chronic lesions in gymnastics and present a real concern for coaches, scientist and clinicians. Previous research has identified injury risk factors during round-off (RO) skills in elite female gymnasts. The aim of this study was to investigate key elbow and wrist joint injury risk factors during different techniques of fundamental cartwheel (CW) and RO skills performed by young female artistic gymnasts. Seventeen active young female gymnasts performed 30 successful trials of both CW and RO from a hurdle step with three different hand positions (parallel (10), T-shape (10) and reverse (10)). Synchronised kinematic (240 Hz) and kinetic (1200 Hz) data were collected for each trial. One-way repeated measures ANOVA and effect size (ES) were used for statistical analysis. The results showed statistically significant differences (P < .05) and large ES (>0.8) among hand positions for peak vertical ground reaction force (VGRF), peak elbow compression force, peak wrist compression force, elbow internal adduction moment and wrist dorsiflexion angle. In conclusion, the parallel and reverse techniques increase peak VGRF, elbow and wrist compression forces, and elbow internal adduction moment. These differences indicate that the parallel and reverse techniques may increase the potential of elbow and wrist injuries in young gymnasts compared with the T-shape technique; this is of particular importance with the high frequency of the performance of these fundamental skills.

The Effect of Stride Length and Lateral Pelvic Tilt on Elbow Torque in Youth Baseball Pitchers.

High elbow torque during a pitch may contribute to injury risk. Our objective was to determine the pitch mechanics associated with elbow varus torque in youth baseball pitchers. Eighteen male youth pitchers (age = 15.5 ± 1.6years) threw 3 fastballs and 3 change-ups from a windup position while undergoing 3-dimensional kinematic analysis. Independent variables included ball release point distance, stride length, lateral pelvic tilt, and ball velocity. Two multiple regression models, separated by pitch type (fastball, change-up) were used to determine the association of independent variables with peak varus torque at the elbow. Fastball and change-up regression models indicated that stride length (β = 0.301, p = .015; β = 0.46, p < .001, respectively) and lateral pelvic tilt (β = -0.50, p < .001; β = -0.25, p = .04, respectively) were significantly associated with peak elbow varus torque. During fastballs, pitch velocity was significantly associated with peak elbow varus torque (β = 0.38, p = .002), while release point distance was significantly associated with peak elbow varus torque during change-ups (β = -0.33, p = .015). Youth pitchers with longer strides and less lateral pelvic tilt demonstrated greater elbow torque regardless of pitch type, while the association of ball velocity and release point to elbow varus torque was dependent on pitch type.

History of cannabis use is associated with altered gait

BackgroundDespite evidence that cannabinoid receptors are located in movement-related brain regions (e.g., basal ganglia, cerebral cortex, and cerebellum), and that chronic cannabis use is associated with structural and functional brain changes, little is known about the long-term effect of cannabis use on human movement. The aim of the current study was to investigate balance and walking gait in adults with a history of cannabis use. We hypothesised that cannabis use is associated with subtle changes in gait and balance that are insufficient in magnitude for detection in a clinical setting. MethodsCannabis users (n=22, 24±6years) and non-drug using controls (n=22, 25±8years) completed screening tests, a gait and balance test (with a motion capture system and in-built force platforms), and a clinical neurological examination of movement. ResultsCompared to controls, cannabis users exhibited significantly greater peak angular velocity of the knee (396±30 versus 426±50°/second, P=0.039), greater peak elbow flexion (53±12 versus 57±7°, P=0.038) and elbow range of motion (33±13 versus 36±10°, P=0.044), and reduced shoulder flexion (41±19 versus 26±16°, P=0.007) during walking gait. However, balance and neurological parameters did not significantly differ between the groups. ConclusionsThe results suggest that history of cannabis use is associated with long-lasting changes in open-chain elements of walking gait, but the magnitude of change is not clinically detectable. Further research is required to investigate if the subtle gait changes observed in this population become more apparent with aging and increased cannabis use.

Comparison of the increase of both muscle strength and hypertrophy of biceps brachii muscle in strengthening exercise with low-intensity resistance training with and without the application of blood flow restriction and high-intensity resistance training

Background: Strengthening exercise is an important component of rehabilitation programs. Recently, it is reported that strengthening exercise with low-intensity resistance training (20-30% of 1 Repetition Maximum) combined with the application of blood flow restriction potentially increases muscle strength and induces muscle hypertrophy as well.Objective: This study aims to compare the increase in muscle strength and hypertrophy among the muscles trained with high-intensity resistance training (HIRT), low-intensity resistance training combined with the application of blood flow restriction using a sphygmomanometer cuff (LIRT+BFR) and low-intensity resistance training (LIRT) alone. Method: The subjects (n=18) are randomly and equally divided into three groups, those are the groups getting the strengthening exercise for left Biceps Brachii muscle with HIRT (70% of 1 RM), LIRT (30% of 1 RM)+BFR and LIRT (30% of 1 RM). Before starting and after getting the resistance training for five weeks, each subject is measured for the left arm circumference. Results: HIRT and LIRT+BFR produce an increase of the left arm circumference significantly greater than LIRT. However, there is no significant difference in the increase of left arm circumference between the HIRT and LIRT+BFR. There is a significant difference in the increase of the peak torque of left flexion elbow joint among the three groups, either at 60o/s or 120o/s or 180o/s angular velocity. At 60o/s angular velocity, LIRT+BFR produces the greatest increasing of the left elbow peak torque among the three groups. At both 120o/s and 180o/s angular velocity, there is no significant difference in the increase of the peak torque of flexion left elbow joint between HIRT and either LIRT+BFR or LIRT. However, at both 120o/s and 180o/s angular velocity, there is a significant difference in the increase of the peak torque of flexion left elbow joint between LIRT+BFR and LIRT.Conclusion: the strengthening exercise for Biceps Brachii muscle with LIRT+BFR induces the Biceps Brachii muscle hypertrophy and increases the muscle strength more than strengthening exercise with LIRT alone. Compared to the HIRT, LIRT+BFR induces an equal muscle hypertrophy and increases more muscle strength for the trained Biceps Brachii muscle.

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.

Kinematic Predictors of Peak Elbow Varus Moments in Adolescent Baseball Pitchers

High-magnitude elbow joint moments during overhead throwing may lead to acute or overuse injuries, especially to the medial epicondyle physis and ulnar collateral ligament (UCL). During the pitching motion, the UCL is responsible for 54% of the elbow varus moment that is required to resist valgus motion. The identification of kinematic variables that predict high-magnitude elbow varus moments in adolescent baseball pitchers is needed. PURPOSE:To develop a predictive model for peak elbow varus moments in adolescent male pitchers based on overhead throwing kinematic variables. METHODS:Ten male baseball pitchers (14.9±1.1 years; 175.7±6.7 cm; 80.5±17.9 kg) threw three fastball windup pitches while three-dimensional motion data were recorded using a 10 camera, digital motion analysis system (480 Hz). A total of 24 kinematic variables were analyzed at three temporal events occurring during the pitching motion: 1) Lead footstrike (FS), 2) Peak glenohumeral external rotation (GHER), and 3) Ball release (BR). Elbow varus joint moments were normalized to body weight and height. A multiple linear regression (MLR) using the stepwise procedure was employed to identify a predictive model for peak elbow varus moments. RESULTS:The MLR model identified five significant kinematic variables predictive of peak elbow varus moments (adj. R2=0.90, p<0.001). The model revealed that significant predictors of peak elbow varus moments included contralateral trunk lean (CTL) at FS (β=0.007, p<0.001), sagittal lead knee angle (LKA) at FS (β=-0.030, p<0.001), trunk rotation (TR) at FS (β=-0.011, p<0.001), longitudinal glove distance (LGD) at GHER (β=0.002, p=0.001) and release point distance (RPD) (β=0.011, p=0.04). Standardized β values revealed CTL at FS (β=0.699) as the strongest predictor of peak elbow varus moments, followed by LKA (β=-0.289), TR (β=-0.271), LGD (β=0.232) and RPD (β=0.139). CONCLUSIONS: Greater CTL, less flexed LKA and counter-clockwise TR at FS, greater LGD at GHER and greater RPD at BR are tendencies associated with greater elbow varus moments in adolescent male baseball pitchers. Modifying pitching mechanics may reduce excessive elbow varus moments and decrease risk of elbow injury in adolescent pitchers.

Joint torque variability and repeatability during cyclic flexion-extension of the elbow.

BackgroundJoint torques are generally of primary importance for clinicians to analyze the effect of a surgery and to obtain an indicator of functional capability to perform a motion. Given the current need to standardize the functional evaluation of the upper limb, the aim of this paper is to assess (1) the variability of the calculated maximal elbow joint torque during cyclic elbow flexion-extension movements and (2) participant test-retest repeatability in healthy young adults. Calculations were based on an existing non-invasive method including kinematic identification and inverse dynamics processes.MethodsTwelve healthy young adults (male n = 6) performed 10 elbow flexion-extension movement carrying five different dumbbells (0, 1, 2, 3 and 4 kg) with several flexion-extension frequencies (½, 1/3, ¼ Hz) to evaluate peak elbow joint torques.ResultsWhatever the condition, the variability coefficient of trial peak torques remained under 4 %. Bland and Altman plot also showed good test-retest, whatever the frequency conditions for the 0, 1, 2, and 3 kg conditions.ConclusionThe good repeatability of the flexion-extension peak torques represents a key step to standardize the functional evaluation of the upper limb.

The effect of elbow hyperextension on ball speed in cricket fast bowling

ABSTRACTThis study investigates how elbow hyperextension affects ball release speed in fast bowling. A two-segment planar computer simulation model comprising an upper arm and forearm + hand was customised to an elite fast bowler. A constant torque was applied at the shoulder and elbow hyperextension was represented using a damped linear torsional spring at the elbow. The magnitude of the constant shoulder torque and the torsional spring parameters were determined by concurrently matching three performances. Close agreement was found between the simulations and the performances with an average difference of 3.8%. The simulation model with these parameter values was then evaluated using one additional performance. Optimising ball speed by varying the torsional spring parameters found that elbow hyperextension increased ball release speed. Perturbing the elbow torsional spring stiffness indicated that the increase in ball release speed was governed by the magnitude of peak elbow hyperextension and the amount that the elbow recoils back towards a straight arm after reaching peak elbow hyperextension. This finding provides a clear understanding that a bowler who hyperextends at the elbow and recoils optimally will have an increase in ball speed compared to a similar bowler who cannot hyperextend. A fast bowler with 20° of elbow hyperextension and an optimal level of recoil will have increased ball speeds of around 5% over a bowler without hyperextension.

Characterization of Joint Resistance and Performance Degradation of the Extravehicular Mobility Unit Spacesuit

Introduction: The primary objective of this pilot study was to characterize human performance degradations caused by the pressurized Extravehicular Mobility Unit Spacesuit (EMU). Method: This study assessed maximum strength (force) for elbow flexion/extension and shoulder abduction/adduction for three EMU suit conditions. Results: Statistically significant differences were observed between suit conditions during elbow flexion. Differences of practical significant were observed between suit conditions for mean peak elbow flexion and extension, but not for shoulder abduction/adduction. EMU resistance to movement was found to differ based on the direction of movement. Discussion: Characteristics of the EMU spacesuit may reduce performance for some movements and improve performance for others.

Lateral Trunk Lean in Pitchers Affects Both Ball Velocity and Upper Extremity Joint Moments

Background: The incidence of upper extremity injuries in baseball pitchers is increasing. Over the past decade there has been a great deal of research attempting to elucidate the cause of these injuries, focusing mainly on the mechanics of the pitching arm with no examination of other key segments, such as the trunk. This is surprising, as coaches will often comment on trunk position in an effort to improve pitching outcomes. Purpose: To determine the association between contralateral trunk lean and ball velocity and the moments about the elbow and glenohumeral joint. Study Design: Descriptive laboratory study. Methods: A total of 99 pitchers were recruited for this study and underwent a pitching analysis using 3-dimensional motion analysis techniques. A random intercept mixed-effects regression model was used to determine if statistically significant associations existed between contralateral trunk lean (away from the pitching arm side) and ball velocity, as well as the elbow varus moment and glenohumeral internal rotation moment. Results: The results demonstrated that the greatest contralateral trunk lean occurs around the time of the peak elbow varus moment. Statistically significant associations were found between contralateral trunk lean and increased ball velocity (P = .003) indicating that for every 10° increase in contralateral lean, ball velocity increased 0.5 m/s. Results also indicated that for every 10° increase in contralateral lean, elbow varus moments increased by 3.7 N·m and glenohumeral internal rotation moments increased by 2.5 N·m (P < .001 for both). Conclusion: Study findings indicate that the positioning of the trunk plays a substantial role in pitching performance and pitcher injury potential. This work helps to demonstrate the importance of proper trunk mechanics in pitching and highlights the need for future research to understand the contribution of the trunk to pitching mechanics. Clinical Relevance: Pitching coaches and trainers can use the results of this study to stress the importance of proper trunk mechanics in pitching. Specifically, improving core strength and trunk control in an effort to maintain a more upright posture through the pitching cycle can reduce upper extremity joint stresses.

Rowing on a Boat Versus Rowing on an Ergo-meter: A Biomechanical and Electromyographycal Preliminary Study

The present preliminary study aimed to report differences between rowing on a boat and rowing on ergo-meter considering not only kinetics and kinematics but also electromyography for a wider understanding of the motor control patterns. Right elbow and knee kinematics of a 23 years old elite rower was recorded by means of two electrical goniometers. Resultant handle force was calculated respectively from strain gauges applied on the right oar and with an uni-axial load cell fixed on the ergo-meter bar. Eight muscles were considered, referred to right arm, right leg and trunk. The athlete was asked to perform 2minutes rowing on-water at 20 strokes per minute (spm) and 2minutes at 32 spm. Then he performed the same protocol on the rower ergo-meter. Maximal voluntary contractions were recorded for EMG data normalization. Kinematics showed an increase in the elbow peak flexion (+20.3% at 20 spm and +16.6% at 32 spm) and a decrease in the knee peak flexion (-4.5% at 20 spm and -2.8% at 32 spm) rowing on the ergo-meter. Peak force recorded at the right hand was higher in the ergo-meter both at 20 spm (+43.5%) and at 32 spm (+29.8%). Muscle activity was higher in the ergo-meter considering biceps brachii, deltoideus medialis, trapezius trasversalis and vastus medialis. Cross-plots of elbow flexion versus muscle activity and versus hand force showed different coordinative patterns comparing the two experimental conditions. Results of this preliminary study indicated the ergo-meter as a valid training device considering the force at the hand. However, it showed different coordinative patterns with respect to rowing on the water in such a way that it should be carefully employed close to competitions.