Electromagnetic Motion Analysis System Research Articles

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

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

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

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

The biomechanical analysis of the standing throw with run-up

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

Anthropometric Database of the Preschool Children from 2 to 6\xa0Years in Taiwan

Anthropometry is important in product or environment designs based on humanfactors. Specific anthropometric databases should be established for certain ofpopulations, especially for different genders, ages and races. In this study, 5772preschool children (from two to six years old) were recruited. An electromagneticmotion analysis system, measuring tape, an electronic scale and electronic caliperswere used to measure the basic data, structural and postural dimensions. Differencesin stature and weights were found in preliminary comparisons with children of the sameage in Japan and the United States. It is supposed that ethnic diversity leads to variedbody dimensions in children. This study established a large-scale and reliableanthropometric database of preschoolers which provides a practical reference fordesigns aimed at Taiwanese children. Accordingly, it is anticipated that the safety andsuitability of products and environments made for Taiwanese children can advancewith regard to ergonomics.

A Comparison of Cervical Spine Motion After Immobilization With a Traditional Spine Board and Full-Body Vacuum-Mattress Splint.

Background:The National Athletic Trainers’ Association (NATA) advocates for cervical spine immobilization on a rigid board or vacuum splint and for removal of athletic equipment before transfer to an emergency medical facility.Purpose:To (1) compare triplanar cervical spine motion using motion capture between a traditional rigid spine board and a full-body vacuum splint in equipped and unequipped athletes, (2) assess cervical spine motion during the removal of a football helmet and shoulder pads, and (3) evaluate the effect of body mass on cervical spine motion.Study Design:Controlled laboratory study.Methods:Twenty healthy male participants volunteered for this study to examine the influence of immobilization type and presence of equipment on triplanar angular cervical spine motion. Three-dimensional cervical spine kinematics was measured using an electromagnetic motion analysis system. Independent variables included testing condition (static lift and hold, 30° tilt, transfer, equipment removal), immobilization type (rigid, vacuum-mattress), and equipment (on, off). Peak sagittal-, frontal-, and transverse-plane angular motions were the primary outcome measures of interest.Results:Subjective ratings of comfort and security did not differ between immobilization types (P > .05). Motion between the rigid board and vacuum splint did not differ by more than 2° under any testing condition, either with or without equipment. In removing equipment, the mean peak motion ranged from 12.5° to 14.0° for the rigid spine board and from 11.4° to 15.4° for the vacuum-mattress splint, and more transverse-plane motion occurred when using the vacuum-mattress splint compared with the rigid spine board (mean difference, 0.14 deg/s [95% CI, 0.05-0.23 deg/s]; P = .002). In patients weighing more than 250 lb, the rigid board provided less motion in the frontal plane (P = .027) and sagittal plane (P = .030) during the tilt condition and transfer condition, respectively.Conclusion:The current study confirms similar motion in the vacuum-mattress splint compared with the rigid backboard in varying sized equipped or nonequipped athletes. Cervical spine motion occurs when removing a football helmet and shoulder pads, at an unknown risk to the injured athlete. In athletes who weighed more than 250 lb, immobilization with the rigid board helped to reduce cervical spine motion.Clinical Relevance:Athletic trainers and team physicians should consider immobilization of athletes who weigh more than 250 lb with a rigid board.

Effects of plate stiffness on first metatarsophalangeal joint motion during unanticipated cutting and resisted sled pushing in football players

Turf toe, first metatarsophalangeal joint (MTPJ) sprain, is a debilitating injury in football players that is likely the result of excessive dorsiflexion of the hallux. Understanding in-cleat motion of the MTPJ with increased magnitudes of midsole stiffness may help to identify footwear modifications for treatment and injury risk. The purpose was to determine the effects of plate stiffness on in-cleat (anatomical) and footwear MTPJ motion during football–specific movements. Male football players (n = 13) performed two tasks, unanticipated side cutting and weighted sled pushing, with two identical football-specific cleats with different magnitudes of plate stiffness. An electromagnetic motion analysis system with 2 mm sensors was used to assess anatomical (mounted on the foot) and footwear (mounted on the cleat) MTPJ dorsiflexion and ankle dorsiflexion. Repeated measures ANOVAs (p < 0.05) were used to assess statistical differences. Footwear measured MTPJ dorsiflexion was significantly decreased with the stiff cleat compared to the control cleat during side cut (p = 0.04) and weighted sled push (p = 0.02) tasks. However, anatomical measured MTPJ dorsiflexion was not statistically different between cleat conditions (p > 0.05). Anatomical ankle dorsiflexion was increased with the stiff cleat compared to control cleat (p = 0.003). In conclusion, Kinematic footwear differences exist between two football cleats with distinctive magnitudes of plate stiffness. Anatomical MPTJ dorsiflexion, however, was not statistically different between cleats.

Newly acquired arthroscopic skills: Are they transferable during simulator training of other joints?

This randomized study investigates whether novices learning simulation-based arthroscopic skills in one anatomical joint environment can immediately transfer their learnt skills to another joint. Medical students were randomized to a simulated diagnostic knee or shoulder arthroscopic task on benchtop training models. After nine task repetitions over 3weeks on one model, each participant undertook the simulation task of the other anatomical joint. Performance was objectively measured using a validated electromagnetic motion analysis system and a validated global rating scale (GRS). Eighteen students participated; eight started the knee task and ten the shoulder task. All participants demonstrated a learning curve in all parameters during task repetition (time taken, hand path length, number of hand movements and GRS scores; p<0.001) with learning effects >1 SD from initial performance (range 1.1-2.2 SD). When the groups swapped models, there was no immediate evidence of skill transfer, with a significant drop in performance between the final training episode and the transfer task (all parameters p<0.003). In particular, the transfer task performance was no better than the first episode performance on that model by these novices. This study showed basic arthroscopic skills did not immediately transfer to an unfamiliar anatomical environment within a simulated setting. These findings have important clinical implications with regard to surgical training as they potentially challenge the assumption that arthroscopic skills acquired in one joint are universally transferrable to other joints. Future orthopaedic simulation training should aim to deliver exposure to a greater variety of arthroscopic procedures and joint environments. This would allow trainees to become familiar with the different arthroscopic setting before undertaking real surgery and consequently improve patient safety. Therapeutic, Level II.

Seat surface inclination may affect postural stability during Boccia ball throwing in children with cerebral palsy.

The aim of the study was to examine how seat surface inclination affects Boccia ball throwing movement and postural stability among children with cerebral palsy (CP). Twelve children with bilateral spastic CP (3 with gross motor function classification system Level I, 5 with Level II, and 4 with Level III) participated in this study. All participants underwent pediatric reach tests and ball throwing performance analyses while seated on 15° anterior- or posterior-inclined, and horizontal surfaces. An electromagnetic motion analysis system was synchronized with a force plate to assess throwing motion and postural stability. The results of the pediatric reach test (p = 0.026), the amplitude of elbow movement (p = 0.036), peak vertical ground reaction force (PVGRF) (p < 0.001), and movement range of the center of pressure (COP) (p < 0.020) were significantly affected by seat inclination during throwing. Post hoc comparisons showed that anterior inclination allowed greater amplitude of elbow movement and PVGRF, and less COP movement range compared with the other inclines. Posterior inclination yielded less reaching distance and PVGRF, and greater COP movement range compared with the other inclines. The anterior-inclined seat yielded superior postural stability for throwing Boccia balls among children with bilateral spastic CP, whereas the posterior-inclined seat caused difficulty.

Stabilization of 2-Column Thoracolumbar Fractures With Orthoses

A gross anatomic and motion analysis study in cadavers. Assess spinal motion in a cadaveric spinal fracture model and investigate the ability of external orthoses to control this motion. External orthoses are frequently prescribed for patients who have experienced burst fracture of the thoracolumbar spine. Despite the substantial expense involved, there is little data confirming their value. A T12 burst fracture model was created in 5 lightly embalmed cadavers by resecting the anterior and middle columns of the T12 vertebra through a thoracolumbar anterior approach to the spine. An electromagnetic motion tracking and analysis system was used to track angular and linear displacement at the fracture during routine patient maneuvers. Several commonly used orthoses, including an extension brace and both an "off-the-shelf" and custom-molded thoracic-lumbar-sacral orthosis (TLSO), were applied to the cadavers and the affect on fracture site motion was assessed. Application of all 3 styles of brace resulted in angular motion of 8° to 12° in flexion-extension, 11° to 20° in axial rotation, and 8° to 10° of lateral bending. Brace application resulted in linear displacement of 29 to 46 mm in the medial-lateral plane, 21 to 23 mm in the axial plane, and 21 to 37 mm in the anterior-posterior plane. During logrolling maneuvers, TLSO style braces diminished angular motion, although residual motion in the range of 5° remained. TLSO style braces had little effect on linear translation. When placed in a seated position in bed, TLSO style braces diminished flexion and extension modestly, but did not influence lateral bending or linear translation. Extension style braces had no effect on fracture motion during any activity tested. In a cadaver model of a burst fracture, there is surprising angular and linear motion at the fracture during common hospital activities. TLSO orthoses can decrease angular motion but do not effect translation at the fracture. An extension orthosis had no effect on motion at the spinal fracture site.

Paper # 128: Inconsistent Manual Techniques Make Qualitative and Quantitative Analyses of the Pivot Shift Test Difficult in Both ACL-Deficient and Intact Knees

Recent attempts have been made to quantify the results of the pivot shift test. The purpose of this study was to compare clinical grade of the pivot shift with instrumented measures collected simultaneously during the test, as well as to the results of a robotic knee test (RKT). Two complete cadaveric lower bodies (pelvis and bilateral lower extremities) were prepared for testing. All knees were evaluated arthroscopically by a single surgeon. One specimen was noted to be ACL-deficient with moderate arthritic changes, and the other specimen was found to have all ligaments intact with moderate arthritic changes to the medial femoral condyle. Five board-certified orthopaedic surgeons that were blinded to the side and nature of the injury bilaterally performed the following battery of clinical tests on both cadaveric specimens: Lachman, anterior drawer, posterior drawer, pivot shift, dial test at 30° of flexion, and varus and valgus stress tests at both 0° and 30° of flexion. Each surgeon verbally graded laxity during each test, and upon completion of all of the tests, each surgeon gave his impression of diagnosis. The surgeons were blinded to each other's clinical exam results and diagnoses. In addition, electromagnetic sensors were rigidly fixed to each femur and tibia, and the electromagnetic system was used to quantify the amount of anterior tibial translation (ATT), internal rotation (IR), and valgus rotation (VL) during the pivot shift tests. The cadavers were also evaluated using a non-invasive RKT system. The RKT bilaterally cycled the knees into anterior and posterior translation (ATT, PTT), internal and external rotation (IR, ER), and varus and valgus rotation (VR, VL). Three cycles of each motion were performed, and both the amount of torque applied and the rate at which the torque was applied were controlled by the system. Following 3 preconditioning cycles, 3 additional test cycles were performed and the 3-dimensional position and orientation data were collected with an electromagnetic motion analysis system in order to determine 3-dimensional joint kinematics. The amount of ATT and IR that occurred during the pivot shift phenomenon were coupled in order to determine the relative magnitude of medial and lateral compartment translation. Kinematic data collected during the manual and robotic exams were compared with the clinical grade of laxity and diagnoses given by each of the surgeons. When asked to perform the pivot shift test, 4/5 surgeons performed the test consistent with the technique described by Slocum et al, in which the test is initiated with the knee internally rotated in full extension in order to examine for the reduction event of an already subluxated tibia. One surgeon performed the test consistent with the technique described by Losee et al, in which the test is initiated in flexion and is performed to examine for the presence of the subluxation event. All surgeons were in agreement that the intact knee demonstrated negative pivot shift results. On the contrary, while all surgeons responded that the ACL-deficient knee demonstrated a positive pivot shift test, the grades of test ranged from 1 to 2+, with only 2 surgeons agreeing on the grade of laxity. The grade of laxity did not appear to be related to ATT (8.1±0.8 mm), lateral compartment translation (10.3±1.3 mm), IR (5.3°±4.7°), or VL (3.5°±2.9°). The RKT results demonstrated that the maximum amount of ATT was 10.3 mm, maximum IR was 4.2°, and maximum VL was 8.5°. Furthermore, using similar calculations as to what was used during the pivot shift, the amount of lateral compartment translation was determined to 11.3 mm. Clearly the surgeon does not use his ability to kinematically move the tibia pathologically with respect to the femur to determine the pivot grade. No absolute kinematic measures, either individually or combined, correlated with the surgeon's clinical grade of pivot shift. This suggests that the surgeon's clinical grade of pivot shift may not be based upon kinematics alone but may include information related to force, speed and acceleration between the tibia and femur. Furthermore, under clinical situations the amount, the speed, and the acceleration of force application are not controlled between patients or surgeons, thus, contributing to the inconsistencies of the pivot shift grading system currently available.

Precision and Validity of a Clinical Method for Pectoral Minor Length Assessment in Overhead-Throwing Athletes

Methods of assessing pectoral minor length are needed to determine the criterion validity, reliability, and precision of a clinical method for pectoralis minor length assessment. Twentynine overhead-throwing athletes volunteered for this study. All measures were taken with an electromagnetic motion analysis system and Palpation Meter. Pearson correlation coeffi cients were calculated for the average pectoralis minor length values from the electromagnetic motion analysis system and Palpation Meter (0.05) to determine the validity of pectoralis minor length. Intraclass correlation coeffi cients (ICC 2,k) and standard error measures were calculated to determine the intrarater reliability and precision of pectoralis minor length measures. Signifi cant correlations were found between pectoralis minor length measures from the electromagnetic motion analysis system and Palpation Meter for the dominant and nondominant arms. The Palpation Meter was also found to be reliable and precise when measuring pectoralis minor length for the dominant and nondominant arms.

EVALUATION OF INTERNAL ROTATOR MUSCLE FATIGUE ON SHOULDER AND SCAPULAR PROPRIOCEPTION

Background and aim: Fatigue of internal or external rotators of the glenohumeral may alter proprioception in the shoulder joint. Fatigue of shoulder muscles can affect the three-dimentional kinematics of the scapula, and may also alter the glenohumeral and scapular movement pattern, with changes in the scapulohumeral rhythm. Previous studies have shown that with arm elevation, there is a decreased upward rotation of the scapula as well as reduced posterior tilt and external rotation movements with shoulder rotator cuff muscle fatigue. Our aim is to examine the effect of internal rotator fatigue on the proprioception of glenohumeral and scapular active repositioning. Methods: Twenty young healthy subjects with an average age of 20 years were recruited. Each subject performed repetitive concentric exercise (internal rotation) to induce muscles fatigue, which was confirmed by a muscle strength testing using a hand-held dynamometer. Measurement of active repositioning with glenohumeral and scapula repositioning were examined before and after internal rotator fatigue via the three-dimensional (3D) electromagnetic motion analysis system. Results: Fatigue of internal rotators did not affect the glenohumeral and thoracoscapluar joint proprioception (P &gt; 0.05). Conclusion: The findings showed that fatigue of shoulder internal rotators did not contribute to alteration in glenohumeral and scapular proprioception.

Changes in Lumbar Movement in People With Low Back Pain Are Related to Compromised Balance

Comparing people with and without low back pain (LBP). This study aimed to investigate lumbar spine movement and the quality of postural recovery in response to unexpected postural perturbation in people with LBP. People with chronic LBP tend to use lumbar spine motion less frequently for postural control than pain-free individuals, and after voluntary arm movement, they need more time and a greater number of postural adjustments to regain postural equilibrium. We hypothesize that motion of the lumbar spine is altered in people with chronic LBP, and this would be associated with compromised control of postural stability in response to unexpected perturbation. The response to a sudden load imposed by a weight dropped into a box held in the hands was studied in 11 individuals with chronic LBP and matched controls. Lumbopelvic motion was recorded with an electromagnetic motion analysis system. Time to recover balance was calculated from ground reaction forces. People with LBP had a delayed initiation of lumbar spine flexion (angular displacement) (Control = 44.9 [25.1] ms, LBP = 90.2 [42.3] ms, P < 0.001) and took longer to regain postural stability (Control = 460.4 [123.4] ms, LBP = 761.0 [194.2] ms, P < 0.001) after the perturbation. These data provide further evidence that the quality of balance control is compromised in LBP patients and that this is associated with poor use of spinal motion as a component of the postural strategy.

A Comparison of Throwing Kinematics between Youth Baseball Players with and Without a History of Medical Elbow Pain

Risk factors in throwing factors associated to little league elbow have not been adequately explored. Whether these factors also affect the players' performance is also important to elucidate while modifying throwing pattern to reduce injury. The purpose of this study was to compare the differences in throwing kinematics between youth baseball players with or without a history of medial elbow pain (MEP) and to determine the relationship between their throwing kinematics and ball speed. Fifteen players with previous MEP were matched with 15 healthy players by age, height and weight. Throwing kinematics was recorded by an electromagnetic motion analysis system. A foot switch was used for determining foot off and foot contact. Ball speed was recorded with a sports radar gun. The group with a history of MEP demonstrated less elbow flexion angle at maximum shoulder external rotation and had more lateral trunk tilt at ball release compared to the healthy group. The group with a history of MEP also had faster maximum upper torso rotation velocities, maximum pelvis rotation velocities and ball speeds. Maximum shoulder external rotation angle (r = 0.458, P = 0.011), elbow flexion angle at maximum shoulder external rotation (r = -0.637, P = 0.0003), and maximum upper torso rotation velocity (r = 0.562, P = 0.002) had significant correlation with ball speed. Findings of this study can be treated as elbow injury-related factors that clinicians and coaches can attend to when taking care of youth

Changes in sitting posture induce multiplanar changes in chest wall shape and motion with breathing

This study examined the effect of sitting posture on regional chest wall shape in three dimensions, chest wall motion (measured with electromagnetic motion analysis system), and relative contributions of the ribcage and abdomen to tidal volume (%RC/V(t)) (measured with inductance plethysmography) in 7 healthy volunteers. In seven seated postures, increased dead space breathing automatically increased V(t) (to 1.5 V(t)) to match volume between conditions and study the effects of posture independent of volume changes. %RC/V(t) (p<0.05), chest wall shape (p<0.05) and motion during breathing differed between postures. Compared to a reference posture, movement at the 9th rib lateral diameter increased in the thoracolumbar extension posture (p<0.008). In slumped posture movement at the AP diameters at T1 and axilla increased (p<0.00001). Rotation postures decreased movement in the lateral diameter at the axilla (p<0.0007). The data show that single plane changes in sitting posture alter three-dimensional ribcage configuration and chest wall kinematics during breathing, while maintaining constant respiratory function.

Classification of Frontal Plane Rearfoot Motion Patterns During the Stance Phase of Walking

Classification of rearfoot motion patterns would assist in understanding normal rearfoot motion and would facilitate the identification of abnormal motion. We sought to identify common frontal plane rearfoot motion patterns in an asymptomatic population. Frontal plane rearfoot motion was measured with an electromagnetic motion analysis system in 279 asymptomatic individuals during barefoot walking. The coefficient of multiple correlation and visual observation were used to identify similar patterns of rearfoot motion. Four distinct rearfoot motion patterns were identified: pattern 1 consisted of 176 individuals (63.1%) and was labeled "typical" eversion, pattern 2 consisted of 87 individuals (31.2%) and was labeled "prolonged eversion," pattern 3 consisted of nine individuals (3.2%) and was labeled "delayed eversion," and pattern 4 consisted of seven individuals (2.5%) and was labeled "early eversion." Asymptomatic frontal plane rearfoot motion can be classified into four distinct patterns, but most individuals (94.3%) exhibit one of two motion patterns (typical or prolonged eversion).

Providing Training Enhances the Biomechanical Improvements of an Alternative Computer Mouse Design

The purpose of this study is to determine if an alternative mouse promotes more neutral postures and decreases forearm muscle activity and if training enhances these biomechanical benefits. Computer mouse use is a risk factor for developing musculoskeletal disorders; alternative mouse designs can help lower these risks. Ergonomic training combined with alternative input devices could be even more effective than alternative designs alone. Thirty healthy adults (15 males, 15 females) performed a set of computer mouse tasks with a standard mouse and an alternative mouse while an electromagnetic motion analysis system measured their wrist and forearm postures and surface electromyography measured the muscle activity of three wrist extensor muscles. Fifteen participants received no training on how to hold the alternative mouse, whereas the remaining 15 participants received verbal instructions before and during use of the alternative mouse. The alternative mouse was found to promote a more neutral forearm posture compared with the standard mouse (up to 11.5 degrees lower forearm pronation); however, pronation was further reduced when instructions on how to hold the mouse were provided. Wrist extensor muscle activity was reduced for the alternative mouse (up to 1.8% of maximum voluntary contraction lower) compared with the standard mouse, but only after participants received instructions. The alternative mouse design decreased biomechanical exposures; however, instructions enhanced this potential ergonomic benefit of the design. User knowledge and training are important factors when effectively implementing an alternative ergonomic device.

The Function of Brachioradialis

The function of the brachioradialis muscle is controversial. The objective of this study was to determine primary and secondary functions of the brachioradialis under various loading tasks as measured by EMG. Ten healthy individuals (9 men, 1 woman; average age, 34 years +/- 10; average height, 175 cm +/- 7; average weight, 76 kg +/- 13) performed elbow flexion with the forearm in 1 of 3 positions (neutral, pronation, and supination) with 4 different loads (0, 22, 45, and 67 N). The elbow was flexed to 90 degrees as the volunteers performed 2 separate movements: (1) from full supination to neutral and (2) from full pronation to neutral using 4 different loads (0, 9, 18, and 27 N). Each movement started and ended in supination and pronation, respectively. Fine-wire EMG electrodes were placed in the brachioradialis, and kinematic data were collected using an electromagnetic motion analysis system. The EMG data were reported as a percentage of maximal voluntary isometric contraction and were ensemble averaged from 5 trials of each exercise condition for statistical analysis. No difference in muscular activation was found during elbow flexion tasks in the 3 forearm positions. Significantly greater activation was found during concentric (23% maximal voluntary isometric contractions +/- 5% maximal voluntary isometric contractions) than during eccentric (11% maximal voluntary isometric contractions +/- 5% maximal voluntary isometric contractions) phases during elbow flexion. Brachioradialis mean activity during concentric pronation and eccentric supination with the heaviest loads 18 and 27 N was significantly greater than activity during concentric supination and eccentric pronation. The greatest EMG activity recorded from the brachioradialis occurs during elbow flexion tasks regardless of forearm position indicating that the primary function of the brachioradialis is as a consistent elbow stabilizer during flexion tasks. During rotational tasks, more EMG activity was recorded during pronation compared with that during supination tasks indicating a secondary function of the brachioradialis as a pronator.

Kinematic Evaluation of the Modified Weaver-Dunn Acromioclavicular Joint Reconstruction

Background Few reconstructive methods to treat displaced acromioclavicular separations have been evaluated using kinematic data. Hypothesis The modified Weaver-Dunn reconstruction restores intact acromioclavicular joint motion during passive scapular plane abduction. Study Design Controlled laboratory study. Methods Acromioclavicular joint motion was recorded during passive humeral elevation in 3 states: an intact shoulder, an “injured” state in which the acromioclavicular and coracoclavicular ligaments were transected, and finally in a reconstructed state using a modified Weaver-Dunn reconstruction. Measurements were taken with an electromagnetic motion analysis system attached to rigid pins placed in the clavicle, scapula, humerus, and sternum during passive scapular plane humeral elevation. Results Total translatory motion of the acromioclavicular joint in the cut state was significantly greater than both the intact and reconstructed states in the medial/lateral (intact, 4.3 mm; cut, 7.9 mm; reconstructed, 2.6 mm), anterior/posterior (intact, 4.8 mm; cut, 6.1 mm; reconstructed, 4.9 mm), and superior/inferior (intact, 4.1 mm; cut, 8.0 mm; reconstructed, 4.8 mm) directions. The maximum and minimum positions of the reconstructed state were significantly more anterior and inferior than in the intact state. A significant increase in acromioclavicular axial rotation was also found between the intact and cut state. Conclusion The modified Weaver-Dunn reconstruction was found to restore motion of the acromioclavicular joint to near-intact values, but created a more anterior and inferior position of the clavicle with respect to the acromion. Clinical Relevance These kinematic data support the modified Weaver-Dunn reconstruction as a kinematically sound procedure to treat displaced acromioclavicular joint injuries.

Smaller external notebook mice have different effects on posture and muscle activity

Background. Extensive computer mouse use is an identified risk factor for computer work-related musculoskeletal disorders; however, notebook computer mouse designs of varying sizes have not been formally evaluated but may affect biomechanical risk factors. Methods. Thirty adults performed a set of mouse tasks with five notebook mice, ranging in length from 75 to 105 mm and in width from 35 to 65 mm, and a reference desktop mouse. An electro-magnetic motion analysis system measured index finger (metacarpophalangeal joint), wrist and forearm postures, and surface electromyography measured muscle activity of three extensor muscles in the forearm and the first dorsal interrosseus. Findings. The smallest notebook mice were found to promote less neutral postures (up to 3.2° higher metacarpophalangeal joint adduction; 6.5° higher metacarpophalangeal joint flexion, 2.3° higher wrist extension) and higher muscle activity (up to 4.1% of maximum voluntary contraction higher wrist extensor muscle activity). Participants with smaller hands had overall more non-neutral postures than participants with larger hands (up to 5.6° higher wrist extension and 5.9° higher pronation); while participants with larger hands were more influenced by the smallest notebook mice (up to 3.6° higher wrist extension and 5.5% of maximum voluntary contraction higher wrist extensor values). Self-reported ratings showed that while participants preferred smaller mice for portability; larger mice scored higher on comfort and usability. Interpretation. The smallest notebook mice increased the intensity of biomechanical exposures. Longer term mouse use could enhance these differences, having a potential impact on the prevention of work-related musculoskeletal disorders.