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1.
The aim of this study was to examine the occurrence of the sticking region by examining how three different grip widths affect the sticking region in powerlifters’ bench press performance. It was hypothesised that the sticking region would occur at the same joint angle of the elbow and shoulder independent of grip width, indicating a poor mechanical region for vertical force production at these joint angles. Twelve male experienced powerlifters (age 27.7 ± 8.8 years, mass 91.9 ± 15.4 kg) were tested in one repetition maximum (1-RM) bench press with a narrow, medium and wide grip. Joint kinematics, timing, bar position and velocity were measured with a 3D motion capture system. All participants showed a clear sticking region with all three grip widths, but this sticking region was not found to occur at the same joint angles in all three grip widths, thereby rejecting the hypothesis that the sticking region would occur at the same joint angle of the elbow and shoulder independent of grip width. It is suggested that, due to the differences in moment arm of the barbell about the elbow joint in the sticking region, there still might be a poor mechanical region for total force production that is joint angle-specific.  相似文献   

2.
Abstract

In the sport of cricket the objective of the “no-ball” law is to allow no performance advantage through elbow extension during ball delivery. However, recently it has been shown that even bowlers with actions that are considered within the law show some elbow extension. The objective of this study was to investigate: [1] the effect of elbow orientation during anatomical landmark digitisation and [2] the choice of upper arm tracking cluster on the measurement of elbow angles during cricket bowling.

We compared the mean elbow angles for four different elbow postures; with the joint flexed at approximately 130°, 90°, in full extension and with the elbow flexed with the humerus internally rotated, and two upper arm clusters in two different situations: [1] during a controlled movement of pure flexion-extension and [2] during cricket bowling. The digitised postures of the anatomical landmarks where the elbow was extended and at 90° of flexion were more repeatable than the other two postures. The recommendation of this study when analysing cricket bowling is to digitise the humeral epicondyles with the joint flexed at 90°, or in full extension, and to relate their positions to an upper arm cluster fixed close to the elbow.  相似文献   

3.
Abstract

The purpose of the study was to determine whether there are differences in kinematics between sprint and distance front crawl specialists when swimming at a distance pace using a six beat kick. Seven sprint and eight distance male specialists performed one maximum 400 m swim through a 6.75 m3 calibrated space recorded by six gen-locked cameras. The following variables were calculated: average swim velocity, stroke length, stroke frequency, upper limb and foot displacement, elbow angle, the shoulder and hip roll angle, duration of the stroke phases and time corresponding to particular events within the stroke cycle relative to hand entry. Differences between the groups were assessed by an independent t-test and effect size (d) calculations for each variable. The groups only differed significantly with respect to the average swim velocity, with the distance swimmers maintaining a greater velocity throughout the 400 m. However, effect sizes were moderate for elbow angle range during the pull phase (d = 0.78) and the total hip roll magnitude (d = 0.76). There was little evidence to suggest that sprint and distance swimmers using a six beat kick pattern differ in technique when swimming at a distance pace and therefore coaches should not encourage the development of different techniques between these groups.  相似文献   

4.
Abstract

The aim of this study was to examine the relationship between shoulder alignment and elbow angle during the delivery action of fast-medium bowlers. The elbow and upper trunk alignment were recorded for 13 high-performance bowlers (mean age 20 years) using a 12-camera Vicon motion analysis system operating at 250 Hz. The three highest velocity trials for “good” and “short” length deliveries were analysed. Results showed that bowlers with a more front-on shoulder alignment at back-foot impact and when the upper arm was horizontal to the ground experienced a significantly greater elbow flexion – extension range when compared with those who had a more side-on orientation at the same point in the delivery action. Bowlers with greater shoulder counter-rotation also recorded higher elbow flexion and subsequently extension during the period from upper arm horizontal to ball release. Shoulder alignment and elbow angles were similar for “short” and “good” length deliveries. It was concluded that bowlers with a more front-on shoulder orientation at back-foot impact demonstrated a higher elbow extension from upper arm horizontal to ball release and are therefore more likely to infringe International Cricket Council elbow tolerance levels, compared with those who adopt a more side-on shoulder orientation at back-foot impact.  相似文献   

5.
Fly-fishing is a popular form of recreation. Recent evidence has associated overhand fly-casting movements with upper extremity pain. However, little research exists on the motions and coordination common to fly-casting. The aim of this study was to establish upper extremity kinematic trends of fly-casting while casting greater line lengths. It was hypothesized that kinematic casting parameters would increase and time between peak angular velocities would decrease with greater line length. Eighteen males participated in the study. Three-dimensional motion capture was conducted to calculate shoulder, elbow, and wrist kinematics during casting conditions of 6.1, 12.2, 18.3, and 24.4 m of line. Multiple analyses of variance were used to assess the condition effect of line length on the kinematic variables (P = 0.05). Overall, total range of movement increased with increasing length of line cast. Peak angular velocity exhibited a proximal-to-distal trend: peak shoulder internal rotation followed by elbow extension, then wrist ulnar deviation. Time between peak shoulder and elbow angular velocities increased significantly as line length increased. Our findings indicate that specific changes in total range of movement accommodate the demands of casting greater lengths of line. Also, joint velocity coordination patterns of fly-casting appear to follow a proximal-to-distal pattern. These findings represent an initial foundation for connections between kinematics and upper extremity pain reported by fly-fisherman.  相似文献   

6.
Current trends in swimming biomechanics are focused on accurate measurements. Nowadays, reliable calibration methods have been proposed to reach an accuracy of about 1 mm on rigid structure. But the question remains about the final accuracy for three-dimensional hand kinematics measurement during the underwater phase of front crawl swimming. Furthermore, most research is based on manual tracking with two or more cameras. In this paper we propose a protocol to acquire three-dimensional hand kinematics when swimming in a specific pool with a motion analysis system behind windows. Results highlight the benefits of using such a system in terms of accuracy and feasibility: the time allowed for post-processing is ten times lower and the quantified improved accuracy is better than with manual tracking.  相似文献   

7.
Abstract

We examined mechanisms of coordination that enable skilled recreational baseball players to make fast overarm throws with their skilled arm and which are absent or rudimentary in their unskilled arm. Arm segment angular kinematics in three dimensions at 1000 Hz were recorded with the search-coil technique from the arms of eight individuals who on one occasion threw with their skilled right arm and on another with their unskilled left arm. Compared with their unskilled arm, the skilled arm had: a larger angular deceleration of the upper arm in space in the forward horizontal direction; a larger shoulder internal rotation velocity at ball release (unskilled arms had a negative velocity); a period of elbow extension deceleration before ball release; and an increase in wrist velocity with an increase in ball speed. It is suggested that some of these differences in arm kinematics occur because of differences between the skilled and unskilled arms in their ability to control interaction torques (the passive torque at one joint due to motion at adjacent joints). It is proposed that one reason unskilled individuals cannot throw fast is that, unlike their skilled counterparts, they have not developed the coordination mechanisms to effectively exploit interaction torques.  相似文献   

8.
Abstract

Magnitudes and timings of kinematic variables have often been used to investigate technique. Where large inter-participant differences exist, as in basketball, analysis of intra-participant variability may provide an alternative indicator of good technique. The aim of the present study was to investigate the joint kinematics and coordination-variability between missed and successful (swishes) free throw attempts. Collegiate level basketball players performed 20 free throws, during which ball release parameters and player kinematics were recorded. For each participant, three misses and three swishes were randomly selected and analysed. Margins of error were calculated based on the optimal-minimum-speed principle. Differences in outcome were distinguished by ball release speeds statistically lower than the optimal speed (misses ?0.12 ± 0.10m · s?1; swishes ?0.02 ± 0.07m · s?1; P < 0.05). No differences in wrist linear velocity were detected, but as the elbow influences the wrist through velocity-dependent-torques, elbow–wrist angle–angle coordination-variability was quantified using vector-coding and found to increase in misses during the last 0.016s before ball release (P < 0.05). As the margin of error on release parameters is small, the coordination-variability is small, but the increased coordination-variability just before ball release for misses is proposed to arise from players perceiving the technique to be inappropriate and trying to correct the shot. The synergy or coupling relationship between the elbow and wrist angles to generate the appropriate ball speed is proposed as the mechanism determining success of free-throw shots in experienced players.  相似文献   

9.
An effective start enhances an athlete's chances of success in ski cross competitions. Accordingly, this study was designed to investigate the biomechanics of start techniques used by elite athletes and assess the influence of different start environments. Seven elite ski cross athletes performed starts indoors on a custom-built ramp; six of these also performed starts on an outdoor slope. Horizontal and vertical forces were measured by force transducers located in the handles of the start gate and a 12-camera motion capture system allowed monitoring of the sagittal knee, hip, shoulder, and elbow kinematics. The starting movement involved Pre, Pull, and Push phases. Significant differences between body sides were observed for peak vertical and resultant forces, resultant impulse, and peak angular velocity of the shoulder joint. Significantly lower peak vertical forces (44 N), higher resultant impulse (0.114 Ns/kg), and knee joint range of motion (12°) were observed indoors. Although movement in the ski cross start is generally symmetrical, asymmetric patterns of force were observed among the athletes. Two different movement strategies, i.e. pronounced hip extension or more accentuated elbow flexion, were utilised in the Pull phase. The patterns of force and movement during the indoor and outdoor starts were similar.  相似文献   

10.
Determining and understanding baseball batting mechanics at various competition levels may help players and coaches identify key kinematics crucial to being a successful hitter. The purpose of this study was to compare batting kinematics across competition levels. Kinematic and temporal data were analysed for 170 male batters (youth n = 33; high school n = 69; college n = 22; professional n = 46) using 3D motion capture (480 Hz). The results showed differences in angular positions between competition levels during the five phases of the swing, with the greatest differences seen between the youth and professional batters. At the instant of ball contact, professional batters held the bat farther away from their body, with greater back shoulder abduction (35°) and less back elbow flexion (78°) compared to youth (27° and 89°, respectively). These differences were associated with greater back elbow extension velocity for professionals (1539°/s) compared to youth (1174°/s). Additionally, higher level batters had higher bat angular and linear velocities compared to the youth batters. As batters progress through their career, they should focus on their back arm by keeping their elbow up and their arm extended in front of them.  相似文献   

11.
Many coaches often instruct swimmers to keep the elbow in a high position (high elbow position) during early phase of the underwater stroke motion (pull phase) in front crawl, however, the high elbow position has never been quantitatively evaluated. The aims of this study were (1) to quantitatively evaluate the “high elbow” position, (2) to clarify the relationship between the high elbow position and required upper limb configuration and (3) to examine the efficacy of high elbow position on the resultant swimming velocity. Sixteen highly skilled and 6 novice male swimmers performed 25 m front crawl with maximal effort and their 3-dimensional arm stroke motion was captured at 60 Hz. An attempt was made to develop a new index to evaluate the high elbow position (Ihe: high elbow index) using 3-dimensional coordinates of the shoulder, elbow and wrist joints. Ihe of skilled swimmers moderately correlated with the average shoulder internal rotation angle (r = ?0.652, P < 0.01) and swimming velocity (r = ?0.683, P < 0.01) during the pull phase. These results indicate that Ihe is a useful index for evaluating high elbow arm stroke technique during the pull phase in front crawl.  相似文献   

12.
ABSTRACT

Knowledge of the kinematic differences that separate highly skilled and less-skilled squash players could assist the progression of talent development. This study compared trunk, upper-limb and racket kinematics between two groups of nine highly skilled and less-skilled male athletes for forehand drive, volley and drop strokes. A 15-camera motion analysis system recorded three-dimensional trajectories, with five shots analysed per participant per stroke. The highly skilled group had significantly (p < 0.05) larger forearm pronation/supination range-of-motion and wrist extension angles at impact than the less-skilled. The less-skilled group had a significantly more “open” racket face and slower racket velocities at impact than the highly skilled. Rates of shoulder internal rotation, forearm pronation, elbow extension and wrist flexion at impact were greater in the drive stroke than in the other strokes. The position of the racket at impact in the volley was significantly more anterior to the shoulder than in the other strokes, with a smaller trunk rotation angular velocity. Players used less shoulder internal/external rotation, forearm pronation/supination, elbow and wrist flexion/extension ranges-of-motions and angular velocities at impact in the drop stroke than in the other strokes. These findings provide useful insights into the technical differences that separate highly skilled from less-skilled players and provide a kinematic distinction between stroke types.  相似文献   

13.
By understanding the normal humeral and scapular kinematics during the kayak stroke, inferences about the relationship of kayaking technique and shoulder injury may be established. The purpose of this study was to describe scapular and humeral kinematics and to compare dominant versus non-dominant symmetry in healthy whitewater kayakers performing the forward stroke. Twenty-five competent whitewater kayakers (mean age: 34.1 ± 9.4 years, mean height: 1.768 ± 0.093 m, mean mass: 78.2 ± 13.0 kg) underwent humeral and scapular kinematic assessment, using an electromagnetic tracking device, while kayaking on a kayak ergometer. Paired t-tests were used to determine symmetry. Scapular and humeral kinematic means and standard deviations at six time points during the kayak stroke were described. Scapular and humeral kinematics were shown to be similar upon bilateral comparison. The greatest potential for injury during the forward stroke may be at thrust paddle shaft vertical when the humerus is maximally elevated in internal rotation and adduction as subacromial structures may be mechanically impinged. The relationship between scapulohumeral kinematics related to injury at other time points are also described.  相似文献   

14.
This modelling study sought to describe the relationships between elbow joint kinematics and wrist joint linear velocity in cricket fast bowlers, and to assess the sensitivity of wrist velocity to systematic manipulations of empirical joint kinematic profiles. A 12-camera Vicon motion analysis system operating at 250 Hz recorded the bowling actions of 12 high performance fast bowlers. Empirical elbow joint kinematic data were entered into a cricket bowling specific “Forward Kinematic Model” and then subsequently underwent fixed angle, angular offset and angle amplification manipulations. A combination of 20° flexion and 20° abduction at the elbow was shown to maximise wrist velocity within the experimental limits. An increased elbow flexion offset manipulation elicited an increase in wrist velocity. Amplification of elbow joint flexion–extension angular displacement indicated that, contrary to previous research, elbow extension range of motion and angular velocity at the time of ball release were negatively related to wrist velocity. Some relationships between manipulated joint angular waveforms and wrist velocity were non-linear, supporting the use of a model that accounts for the non-linear relationships between execution and outcome variables in assessing the relationships between elbow joint kinematics and wrist joint velocity in cricket fast bowlers.  相似文献   

15.
ABSTRACT

This study aimed to describe stationary overhead throwing biomechanics in South African cricketers, considering playing level, and relative to baseball. Kinematics and ground reaction forces were collected during throwing trials. Inverse dynamics was used to calculate joint kinetics. Inter-subject variability was calculated using the coefficient of variance. A one-dimensional statistical parametric mapping ANOVA was conducted to assess differences between the kinematic waveforms in elite and amateur cricketers (p < 0.05). Fifteen cricketers (elite = 8; amateur = 7) participated in this study. The basic parameters of a cricketer’s throwing action are described. Substantial inter-subject variability was noted for all variables, except lumbopelvic movement. Cricketers presented with 74.9 ± 27.3° glenohumeral external rotation and 94.8 ± 23.7° elbow flexion, at maximum external rotation (MER). Amateur cricketers displayed decreased elbow flexion range of motion between 2-14% of the throwing cycle (F = 9.365;p = 0.01); greater shoulder (121.0vs85.9 N; F = 0.36,p = 0.021) and elbow compression (105.6vs72.8 N;F = 0.007,p = 0.043), and superior shoulder force (203.1vs115.5 N;F = 2.43,p = 0.022) at MER, when compared with elite cricketers. Cricketers display similarities to baseball pitchers when throwing overhead from a stationary position. The “preparatory arc” utilised is different to the wind-up noted for baseball. The forces exerted on the shoulder and elbow, in amateur cricketers specifically, are substantially greater at MER and may indicate the potential risk for injury.  相似文献   

16.
ABSTRACT

When learning swinging skills on a bar there has been conflicting advice in the research literature regarding whether to coach the “gold standard” technique to novices. The present study aimed to determine how technique (joint angle time histories) and (inter-limb) coordination changed as novice gymnasts learned a fundamental gymnastics skill (the upstart). It was hypothesised that both technique and coordination would become more like an expert as learning progressed. Eight novice gymnasts, unable to perform an upstart, underwent four months of training, with the number of successful upstarts out of 10 recorded at the start and then every month subsequently. In the first and last sessions motion capture was used to determine joint kinematics. Root mean squared differences for the joint angle time histories and continuous relative phase at the shoulder and hip were calculated between the novices and an expert gymnast. As training progressed technique and coordination became more like the expert gymnast. The more successful novices were better able to time their actions within the swing than the less successful novices. Gymnastics coaches teach towards a “gold standard” technique since being successful at the skill is not the only goal, as considerations for future skill development are made.  相似文献   

17.
Abstract

An analysis system for barbell weightlifting exercises is proposed to record reliable performance and neuromuscular responses. The system consists of surface electromyography (sEMG) synchronized with electrogoniometry and a barbell position transducer. The purpose of this study was to establish the reliability of the three components of the system. Nine males (age 28.9 ± 4.8 years, mass 85.7 ± 15.1 kg) performed squat exercise at three loads on three separate trial days. A data acquisition and software system processed maximal knee angle (flexion), mean power for the concentric phase of squat exercise, and normalized root mean square of the vastus lateralis. Inter-trial coefficients of variation for each variable were calculated as 5.3%, 7.8%, and 7.5% respectively. In addition, knee joint motion and barbell displacement were significantly related to each other (bar displacement (m) = 1.39–0.0057 × knee angle (degress), with goodness-of-fit value, r 2 = 0.817), suggesting knee goniometry alone can represent the kinematics of a multi-joint squat exercise. The proven reliability of the three components of this system allows for real-time monitoring of resistance exercise using the preferred training methods of athletes, which could be valuable in the understanding of the neuromuscular response of elite strength training methods.  相似文献   

18.
Kinematic measurements conducted during bike set-ups utilise either static or dynamic measures. There is currently limited data on reliability of static and dynamic measures nor consensus on which is the optimal method. The aim of the study was to assess the difference between static and dynamic measures of the ankle, knee, hip, shoulder and elbow. Nineteen subjects performed three separate trials for a 10-min duration at a fixed workload (70% of peak power output). Static measures were taken with a standard goniometer (GM), an inclinometer (IM) and dynamic three-dimensional motion capture (3DMC) using an eight camera motion capture system. Static and dynamic joint angles were compared over the three trials to assess repeatability of the measurements and differences between static and dynamic values. There was a positive correlation between GM and IM measures for all joints. Only the knee, shoulder and elbow were positively correlated between GM and 3DMC, and IM and 3DMC. Although all three instruments were reliable, 3D motion analysis utilised different landmarks for most joints and produced different means. Changes in knee flexion angle from static to dynamic are attributable to changes in the positioning of the foot. Controlling for this factor, the differences are negated. It was demonstrated that 3DMC is not interchangeable with GM and IM, and it is recommended that 3DMC develop independent reference values for bicycle configuration.  相似文献   

19.
水下三维物空间坐标的重构精度分析   总被引：1，自引：0，他引：1  
目的:水下运动学数据的精度对于游泳项目的技术动作分析十分重要,利用防水摄像装置对标定框架上的有效点在水下和空气中进行三维重构,旨在验证不同测试环境和不同大小的标定空间对水下三维重构精度的影响,为水下游泳的器材研发提供一定的参考和依据。方法:2台水下摄像机同步拍摄放置在泳池里的标定框架(2 m×2 m×1 m),标定框架采取2种不同大小的标定空间,分别对同样数目的控制点(12个)和有效点(4个)分别在水下和空气中进行三维重构,重构精度通过4个有效点的均方根(RMS)重构误差来表示,利用DLT算法和ARIEL软件进行标定重构和数字化。结果发现,在整体标定空间控制点的RMS重构误差在X、Y、Z轴上为:(ⅰ)5.60 mm、10.44 mm和3.74 mm(水下),(ⅱ)4.89 mm、4.89 mm和3.96 mm(空气);局部标定空间为(ⅰ)5.29 mm、9.18 mm和3.02 mm(水下)(ⅱ)1.44 mm、1.11 mm和3.25 mm(空气)。结论:由于光线折射不论标定空间的大小,水下三维重构所得到的RMS重构误差都高于空气中的测量,Y轴最为明显;随着标定空间的增大,两种测试环境下的RMS重构误差均随之增大。  相似文献   

20.
ABSTRACT

Although polo is a well-known equestrian sport, it is fundamentally misunderstood. The purpose of this study was to examine trunk and upper extremity kinematics and segmental velocities during the offside forehand polo swing between male and female athletes. Ten female and 17 male professional polo athletes volunteered. An electromagnetic tracking system collected kinematic data at 100 Hz while participants performed three offside forehand polo swings from a stationary wooden horse. One-way ANOVAs revealed statistically significant differences (p<0.05) in all kinematic variables and segmental velocities. Specifically, males exhibited a greater mean difference (MD=23°) of trunk flexion at take away (TA) and top of backswing (TOB)(MD=29°) trunk lateral flexion at ball contact (BC)(MD=23°), trunk rotation at TA(MD=97°) and TOB(MD=118°), shoulder abduction at TOB(MD=64°), and shoulder elevation at TOB(MD=13°) and BC(MD=40°). Females displayed greater trunk rotation at BC(MD=91°), shoulder elevation at TA(MD=19°), and elbow flexion at TA(MD=90°). Additionally, females generated greater segmental velocities early in the swing, while the males generated velocity later. The movement patterns observed amongst the males suggest energy is being transferred more efficiently along the kinetic chain, thus more efficient swing mechanics, but further investigation into the role of the trunk and lumbopelvic-hip complex in reference to the polo swing is warranted.  相似文献   

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