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1.
Wrist injuries are frequently observed after falls in snowboarding. In this study, laboratory experiments mimicking forward and backward falls were analysed. In six different falling scenarios, participants self-initiated falls from a static initial position. Eighteen volunteers conducted a total of 741 trials. Measurements were taken for basic parameters describing the kinematics as well as the biomechanical loading during impact, such as impact force, impact acceleration, and velocity. The effective mass affecting the wrist in a fall also was determined. The elbow angle at impact showed a more extended arm in backward falls compared to forward falls, whereas the wrist angle at impact remained similar in forward and backward falls. The study results suggest a new performance standard for wrist guards, indicating the following parameters to characterize an impact: an effective mass acting on one wrist of 3–5 kg, an impact angle of 75° of the forearm relative to the ground, and an impact velocity of 3 m/s.  相似文献   

2.
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   

3.
The purpose of this study was to assess the contributions of racket arm joint rotations to the racket tip velocity at ball impact in table tennis topspin backhands against topspin and backspin using the method of Sprigings et al. (1994). Two cine cameras were used to determine three-dimensional motions of the racket arm and racket, and the contributions of the rotations for 11 male advanced table tennis players. The racket upward velocity at impact was significantly higher in the backhand against backspin than against topspin, while the forward velocity was not significantly different between the two types of backhands. The negative contribution of elbow extension to the upward velocity was significantly less against backspin than against topspin. The contribution of wrist dorsiflexion to the upward velocity was significantly greater against backspin than against topspin. The magnitudes of the angular velocities of elbow extension and wrist dorsiflexion at impact were both similar between the two types of backhands. Our results suggest that the differences in contributions of elbow extension and wrist dorsiflexion to the upward velocity were associated with the difference in upper limb configuration rather than in magnitudes of their angular velocities.  相似文献   

4.
Wrist movements have been identified as an important factor in producing a successful golf swing, with their complex motion influencing both club head velocity and orientation. However, a detailed analysis of wrist angles is lacking in the literature. The purpose of this study was to determine kinematics across wrists and club head characteristics during the golf swing under weak, neutral and strong grip conditions. Twelve professional male golfers executed 24 shots using a driver under three grip conditions. A six degrees of freedom analysis of the hand with respect to the distal forearm was performed using a 10-camera three-dimensional motion capture system. Differences in joint angles were explored using repeated measures ANOVAs at key swing events (onset, top of backswing and impact), in addition club head velocity and clubface angle at impact were also explored. Main findings revealed significant differences in flexion/extension and internal/external rotation for both wrists at all swing events, whereas fewer significant interactions were found in ulnar/radial deviation across grips for both wrists at all events. Clubface angle only differed significantly between the weak and the strong and neural grips, presenting a more ‘open’ clubface to the intended hitting direction. This study is the first to explore tri-planar wrist movement and the effect of different grips, such analysis has implications for coaching knowledge and practice and should inform future research into different aspects of skill, technique analysis and may inform injury mechanisms/prevention.  相似文献   

5.
Smoothing to obtain accurate position and velocity data near impacts in sport biomechanics studies is complicated by the accelerations of impact, endpoint effects and the smoothing technique used. Wrist goniometric data with two levels of random noise added were used to examine three endpoint modelling conditions for obtaining accurate position and velocity data at impact in the tennis forehand. The common approach of smoothing through impact created distortions of the position signal up to 100 ms before impact and resulted in consistent underestimations (-3.2%) of wrist angle and angular velocity (-67.9%) at impact. New linear and polynomial extrapolation conditions smoothed with all techniques provided lower root mean squared errors than the smoothing-through-impact condition, with discrete wrist positions at impact within 1.1% of the criterion data. Both the new linear and polynomial conditions can be used to make more accurate angular position and velocity estimates for tennis impacts, whereas the smoothing-through-impact condition creates spurious decreases in speed before impact that in the past have been assumed to be aspects of skillful movement.  相似文献   

6.
定距离原地投篮的弧线轨迹主要取决于出手速度和出手角度。为了探究优秀青年男子运动员不同距离原地投篮命中率的各影响因素,采用平面定机高速摄影和运动技术解析法,采集12名U16中国国家男子篮球运动员罚篮、中投和三分投球中篮过程投篮手臂的腕、肘、肩、膝等相关关节的线速度和角速度等参数,运用关联度和回归分析(Matlab2018a)探究规律。发现8项因素对原地投篮对命中率有不同程度的影响,其中,球初始高度、球离手高度、腕关节速度和膝关节速度4项因素,通过投篮角度和投篮速度对不同距离投篮中命中率的影响最大。  相似文献   

7.
Smoothing to obtain accurate position and velocity data near impacts in sport biomechanics studies is complicated by the accelerations of impact, endpoint effects and the smoothing technique used. Wrist goniometric data with two levels of random noise added were used to examine three endpoint modelling conditions for obtaining accurate position and velocity data at impact in the tennis forehand. The common approach of smoothing through impact created distortions of the position signal up to 100 ms before impact and resulted in consistent underestimations (-3.2%) of wrist angle and angular velocity (-67.9%) at impact. New linear and polynomial extrapolation conditions smoothed with all techniques provided lower root mean squared errors than the smoothing-through-impact condition, with discrete wrist positions at impact within 1.1% of the criterion data. Both the new linear and polynomial conditions can be used to make more accurate angular position and velocity estimates for tennis impacts, whereas the smoothing-through-impact condition creates spurious decreases in speed before impact that in the past have been assumed to be aspects of skilful movement.  相似文献   

8.
The penalty throw in water polo: a cinematographic analysis   总被引：1，自引：0，他引：1  
Three-dimensional (3-D) high-speed cinematography was used to record the penalty throw in water polo by six elite male (M) and six elite female (F) players. The direct linear transformation technique (DLT) was used in the 3-D space reconstruction from 2-D images recorded via laterally placed phase-locked cameras operating at 200 Hz. Five of the twelve subjects lifted the ball from underneath at the start of the throw whilst the remaining subjects opted for a rotation lift. As the ball was brought behind the head the females used very little hip and shoulder rotation compared to the male players so that four of the six female subjects were square on to the target at the rear point. At the completion of the backswing the wrist was flexed to a similar angle (M-162 degrees; F-158 degrees); the elbow angle showed significantly greater flexion for females (85 degrees) than males (107 degrees). During the forward swing, from rear point to release, the wrist joint of the female players flexed from a rear point angle of 158 degrees to 148 degrees at release. The wrist movement for male subjects was different from the females in that it flexed from 162 degrees to 147 degrees, 0.10 s prior to release and then extended to 159 degrees at palmar release before again flexing to 156 degrees at release. The amount of elbow extension during the forward swing was 48 degrees for both groups; however, the females actually released the ball with the forearm vertical (89 degrees) compared to the male forearm angle of 78 degrees. Maximum angular velocity of the wrist and elbow occurred at release for 9 of the 12 subjects. Both the wrist and elbow joints (F-148 degrees; M-156 degrees at wrist and F-126 degrees; M-148 degrees at elbow) demonstrated greater flexion at release in female subjects, compared with males. Maximum linear endpoint velocities for the forearm and hand segments occurred at ball release resulting in mean ball velocities of 19.1 m s-1 and 14.7 m s-1 for male and female subjects respectively.  相似文献   

9.
In snowboarding, the wrist is the most common injury site, as snowboarders often put their arms out to cushion a fall. This can result in a compressive load through the carpals coupled with wrist hyperextension, leading to ligament sprains or carpal and forearm bone fractures. Wrist protectors are worn by snowboarders in an effort to reduce injury risk, by decreasing peak impact forces and limiting wrist extension to prevent hyperextension during falls. There is no international standard or universally accepted performance specification that snowboarding wrist protectors should conform to, resulting in an inability to judge which designs offer the best protection. This study investigated how surrogate arm design affected the stiffness of wrist protectors during quasi-static mechanical testing. Three surrogate arms with increasing design complexity were used to test three wrist protectors. The results show that surrogate design does influence the stiffness of snowboarding wrist protectors. Given that the surrogate does influence protector performance, it is recommended that a standard surrogate design is established for research and product testing.  相似文献   

10.
Three‐dimensional (3‐D) high‐speed cinematography was used to record the penalty throw in water polo by six elite male (M) and six elite female (F) players. The direct linear transformation technique (DLT) was used in the 3‐D space reconstruction from 2‐D images recorded via laterally placed phase‐locked cameras operating at 200 Hz. Five of the twelve subjects lifted the ball from underneath at the start of the throw whilst the remaining subjects opted for a rotation lift. As the ball was brought behind the head the females used very little hip and shoulder rotation compared to the male players so that four of the six female subjects were square on to the target at the rear point. At the completion of the backswing the wrist was flexed to a similar angle (M‐162°; F‐158°); the elbow angle showed significantly greater flexion for females (85°) than males (107°).

During the forward swing, from rear point to release, the wrist joint of the female players flexed from a rear point angle of 158° to 148° at release. The wrist movement for male subjects was different from the females in that it flexed from 162° to 147°, 0.10 s prior to release and then extended to 159° at palmar release before again flexing to 156° at release. The amount of elbow extension during the forward swing was 48° for both groups; however, the females actually released the ball with the forearm vertical (89°) compared to the male forearm angle of 78°. Maximum angular velocity of the wrist and elbow occurred at release for 9 of the 12 subjects. Both the wrist and elbow joints (F‐148°; M‐156° at wrist and F‐126°; M‐148° at elbow) demonstrated greater flexion at release in female subjects, compared with males. Maximum linear endpoint velocities for the forearm and hand segments occurred at ball release resulting in mean ball velocities of 19.1 m s ‐1 and 14.7 m s‐ 1 for male and female subjects respectively.  相似文献   

11.
将交谊舞练习者分为跳舞时重心起伏突然(不平稳)和平稳型两类,旨在探索不同舞姿练习者在正常步行中是否表现出不同的撞击震荡吸收能力。测试中要求受试者以各自正常的步速行走,在胫骨和头部分别用体表加速度计记录其加速度变化,并同步摄下其步态而得到相关运动学参数。结果表明:正常行走时平稳型练习者的震荡吸收较不平稳型好;不平稳型练习者行走时的膝角、踝角峰值和踝关节角度变化范围较平稳型均大,且有显著性。认为,采用合理的舞姿(平稳型)将有利于提高交谊舞练习者的整体震荡吸收能力和改善踝关节背屈控制能力和全身协调能力。  相似文献   

12.
Purpose

The purposes of this study were to: (a) examine the effect of experience and goal constraints (speed, accuracy) on kicking patterns; (b) determine if effective striking mass was independent of ankle velocity at impact; and (c) determine the accuracy of kicks relative to independent factors.

Method

Twenty participants were recruited to kick at 3 different velocities with and without an accuracy requirement. Multivariate analysis of variance determined if relative timing of joint angular velocities changed during the kick. Chi-square analysis determined if calculated effective mass was independent of ankle velocity at impact. Analysis of variance (ANOVA) was used to examine differences in absolute constant error and variable error according to independent factors.

Results

Results indicated that experience and speed affect absolute timing of joint velocities with no changes in the relative timing of peak joint velocity across independent factors. Chi-square analysis indicated that calculated effective mass is not independent of ankle velocity. ANOVA indicated that experienced performers displayed less variability error than did inexperienced performers.

Conclusion

It was concluded that: (a) Experience, velocity, and accuracy do not affect the relative timing of kicks; (b) kickers trade ankle velocity at impact for greater effective striking mass and ball velocity; and (c) variability in ball placement is affected by experience.  相似文献   

13.
The contribution of core neuromuscular control to the dynamic stability of badminton players with and without knee pain during backhand lunges has not been investigated. Accordingly, this study compared the kinematics of the lower extremity, the trunk movement, the muscle activation and the balance performance of knee-injured and knee-uninjured badminton players when performing backhand stroke diagonal lunges. Seventeen participants with chronic knee pain (injured group) and 17 healthy participants (control group) randomly performed two diagonal backhand lunges in the forward and backward directions, respectively. This study showed that the injured group had lower frontal and horizontal motions of the knee joint, a smaller hip–shoulder separation angle and a reduced trunk tilt angle. In addition, the injured group exhibited a greater left paraspinal muscle activity, while the control group demonstrated a greater activation of the vastus lateralis, vastus medialis and medial gastrocnemius muscle groups. Finally, the injured group showed a smaller distance between centre of mass (COM) and centre of pressure, and a lower peak COM velocity when performing the backhand backward lunge tasks. In conclusion, the injured group used reduced knee and trunk motions to complete the backhand lunge tasks. Furthermore, the paraspinal muscles contributed to the lunge performance of the individuals with knee pain, whereas the knee extensors and ankle plantar flexor played a greater role for those without knee pain.  相似文献   

14.
目的:观察3个月综合锻炼对社区老年人步态的影响.方法:研究对象为自愿参加本次测试的控江社区60～80岁老年女性16名.志愿者参加每周3次、每次1.5小时、为期3个月的针对性综合锻炼干预,步态指标由VICON系统与KISTLER测力台进行数据同步采集,并使用VISUAL3D软件进行分析.结果:经过运动干预后,志愿者步态指标发生显著变化,表现为步长增加(0.54 ±0.07m VS 0.60±0.06 m,P＜0.01)、步速加快(1.10±0.18 VS1.29±0.22 m/s,P＜0.01)、双支撑时相缩短(24.10％±5.10％ VS 21.08％±3.99％,P＜0.01)、步态各周期中髋、膝、踝关节活动幅显著加大.结论:简易的综合性锻炼计划对老年人步态有显著的改善效果,建议可作为预防老年人跌倒的运动干预手段.  相似文献   

15.
Laceration injuries account for up to 23% of injuries in rugby union. They are frequently caused by studded footwear as a result of a player stamping onto another player during the ruck. Little is known about the kinetics and kinematics of rugby stamping impacts; current test methods assessing laceration injury risk of stud designs therefore lack informed test parameters. In this study, twelve participants stamped on an anthropomorphic test device in a one-on-one simulated ruck setting. Velocity and inclination angle of the foot prior to impact was determined from high-speed video footage. Total stamping force and individual stud force were measured using pressure sensors. Mean foot inbound velocity was 4.3 m ? s?1 (range 2.1–6.3 m ? s?1). Mean peak total force was 1246 N and mean peak stud force was 214 N. The total mean effective mass during stamping was 6.6 kg (range: 1.6–13.5 kg) and stud effective mass was 1.2 kg (range: 0.5–2.9 kg). These results provide representative test parameters for mechanical test devices designed to assess laceration injury risk of studded footwear for rugby union.  相似文献   

16.
The aim of this study was to establish differences in intra-cyclic horizontal velocity variation of the body's centre of mass in breaststroke swimmers with flat and undulating styles. Vertical eel-like body waving and trunk rotations were measured to distinguish styles. To reconstruct trunk extension and kyphosis in the poorly visible zone close to the water surface, a semi-automated video-analysis system was developed. From 45 internationallevel swimmers examined, two groups of women and two groups of men were identified, those using the most undulating and those using the flattest styles. Among the men with the flattest style, the maximum and minimum horizontal velocity of the body's centre of mass differed by 76% from the mean swimming velocity; among the women with the most undulating style, the figure was 53%. In the most undulating style, less horizontal velocity variation of the body's centre of mass could be explained by movements of the body parts above the water surface, creating a transfer of momentum: a quick backward upper trunk rotation generates resistance and a quick forward shoulder girdle and upper arm movement, followed by a quick forward upper trunk and head rotation, generates propulsion. In addition, during an upward leg kick, some swimmers generated propulsion similar to that seen in eels.  相似文献   

17.
ABSTRACT

To maintain the accuracy of squash shots under varying conditions, such as the oncoming ball’s velocity and trajectory, players must adjust their technique. Although differences in technique between skilled and less-skilled players have been studied, it is not yet understood how players vary their technique in a functional manner to maintain accuracy under varying conditions. This study compared 3-dimensional joint and racket kinematics and their variability between accurate and inaccurate squash forehand drives of 9 highly skilled and 9 less-skilled male athletes. During inaccurate shots, less-skilled players hit the ball with a more open racket, demonstrating a difference in this task-relevant parameter. No joint kinematic differences were found for accuracy for either group. Coordinated joint rotations at the elbow and wrist both displayed a “zeroing-in” effect, whereby movement variability was reduced from the initiation of propulsive joint rotation to a higher consistency at ball-impact; potentially highlighting the “functionality” of the variability prior to the impact that enabled consistent task-relevant parameters (racket orientation and velocity) under varying conditions. Further, highly skilled players demonstrated greater consistency of task-relevant parameters at impact than less-skilled players. These findings highlight the superior ability of highly skilled players to adjust their technique to achieve consistent task-relevant parameters and a successful shot.  相似文献   

18.
The effective numerical method proposed by Shimamuraet al. (2007) is extended to predict the ball motion in a draw shot as well as a follow shot in billiards. The extended method is verified experimentally using a high speed camera. It is observed in the experiment that a ball rotates backwards with a lot of slip (between ball and table) at first and then rotates forwards in a draw shot. Such a ball motion is predicted quantitatively with the numerical method. Numerical simulations are performed to investigate the effects of material properties of a cue on ball behaviour in follow and draw shots and it is found that the impact force increases with increasing stiffness of the shaft in both follow and draw shots, while its duration time is shortened with increasing wave velocity in the shaft for both shots. It is also found that there is a certain shaft stiffness that gives the minimum ball centre velocity, the minimum angular velocity, the minimum slip velocity between ball and table and also the minimum time when the backward rotation changes to a forward one in a draw shot, while the ball centre velocity and the angular velocity increase with increasing shaft stiffness in a follow shot.  相似文献   

19.
The purpose of this study was to determine hip joint kinetics during a table tennis topspin forehand, and to investigate the relationship between the relevant kinematic and kinetic variables and the racket horizontal and vertical velocities at ball impact. Eighteen male advanced table tennis players hit cross-court topspin forehands against backspin balls. The hip joint torque and force components around the pelvis coordinate system were determined using inverse dynamics. Furthermore, the work done on the pelvis by these components was also determined. The peak pelvis axial rotation velocity and the work done by the playing side hip pelvis axial rotation torque were positively related to the racket horizontal velocity at impact. The sum of the work done on the pelvis by the backward tilt torques and the upward joint forces was positively related to the racket vertical velocity at impact. The results suggest that the playing side hip pelvis axial rotation torque exertion is important for acquiring a high racket horizontal velocity at impact. The pelvis backward tilt torques and upward joint forces at both hip joints collectively contribute to the generation of the racket vertical velocity, and the mechanism for acquiring the vertical velocity may vary among players.  相似文献   

20.
Three-dimensional (3-D) high-speed cinematographic techniques were used to record topspin and backspin forehand approach shots hit down-the-line by high-performance players. The direct linear transformation (DLT) technique was used in the 3-D space reconstruction from 2-D images recorded via laterally placed phase-locked cameras operating at 200 Hz. A Mann-Whitney U-test was calculated for the different aspects of the topspin and backspin shots to test for significance (P less than 0.05). A significant difference was recorded between topspin and backspin shots in the angle of the racket at the completion of the backswing. The racket was taken 0.48 rad past a line drawn perpendicular to the back fence for topspin trials, but only rotated 0.86 rad from a line parallel to the net in the backspin shot. Maximum racket velocities occurred prior to impact and were significantly higher in topspin (26.5 m s-1) compared to backspin (16.6 m s-1) trials. This resulted in the topspin trials recording a significantly higher ball velocity compared to backspin trials (27.6 m s-1 vs 21.7 m s-1). Pre-impact racket trajectories revealed that in topspin shots the racket moved on an upward path of 0.48 rad while in backspin shots it moved down at an angle of 0.34 rad. In the topspin trials impact occurred significantly further forward of the front foot than in backspin shots (0.26 m vs 0.05 m) while the angle of the racket was the same for both strokes (0.14 rad behind a line parallel to the net). The mean angle of the racket-face at impact was inclined backwards by 0.11 rad for backspin strokes and rotated forward by 0.13 rad for topspin strokes. Angles of incidence and reflection of the impact between the ball and the court showed that backspin trials had larger angles of incidence and reflection than topspin strokes.  相似文献   

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