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1.
在现代乒乓球技术中，特别是改用40mm大球的今天，不断加快挥拍的速度，增大击球力量是提高竞技水平的重要途径之一。然而，要测定乒乓球运动员极快的挥拍速度，必须使用高速摄影等特殊手段，一般很难完成。为寻求一种简便易行的办法，我们对击球瞬间挥拍速度与被击出的球飞出距离的关系进行了实验研究。结果发现，挥拍速度与球的飞出距离两变量间存在显著的相关关系。在使用40mm乒乓球的情况下，相关系数男子为0．881(P(0．01)，女子为0．889(P(0．01)。用测量扣杀时球飞出距离来推算击球瞬间的挥拍速度，作为一种简便方法是可行的。 相似文献
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<正> 乒乓球挥拍加速度直接影响击球力量、速度、旋转,它关系着击球的技术质量。长期以来,人们对于运动员技术质量的优劣,只能用眼睛衡量。能不能通过一种方法测定出挥拍加速度,速度及其它运动学及动力学参数呢?从1985年以来,我们对陕西体工队队员和西安体院专项班学生做了二十七人次的正手攻球、拉孤圈球加速度的测试。现将我们测试方法及分析结果介绍如下,供教练员运动员们参考。 相似文献
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打乒乓球每打一板后,球除了沿某一曲线飞行以外,一般同时绕某一通过球心的轴线旋转。旋转着的球的飞行路线,以及它碰到球台、球拍时的弹跳性能,都跟不转的球有很大差别。也就是说乒乓球的飞行路线以及球在球台、球拍上的弹跳性能,会由于球的自转而产生一系列的“异常”现象。因此,回击每一板来球都必须事先弄清楚球的旋转性能,才能决定正确的打法(例如决定球拍在空间方向、挥拍方向、挥拍速度等等)。 相似文献
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击球时充分利用下身的力量 阿加西的击球动作特点就是快而有力地挥拍以及较大的随挥动作。无论是对慢速球还是对快速球,阿加西的随挥动作都比较大。此外,他的击球瞬间的向内翻手腕对控制球也很有好处。 大的随挥动作可以有利于将击出的球压住。如果有意识地提高挥拍的速度,随挥动作自然也就比较大。此外,还要注意将下身力量作用到击球瞬间,在挥拍时利用身体的转动可以增加击球的力量。 相似文献
7.
乒乓球正手攻球动作的生物力学分析与评价 总被引：1，自引：0，他引：1
从生物力学的角度,对乒乓球正手攻球的动作效果进行分析与评价.通过对正手攻球动作的上肢摆动挥拍、躯干转动、下肢蹬伸肌群工作特点的分析,认为乒乓球攻球效果与动作速度、动作方向、动作时间、动作幅度有直接的关系。 相似文献
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<正>正手拉球技术是乒乓球技术中最基本也是最重要的技术之一,其特点是站位比较近、速度比较快、线路活和稳健性好,是回击发球、搓球、削球等下旋球的一种必备技术。但在训练和比赛中,学生的失误率较高,经常出现挥拍动作过大、高重心击球的现象。笔者 相似文献
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网球底线反手切削球技术划分及运动学参数比较分析 总被引：1，自引：0，他引：1
黄建军 《沈阳体育学院学报》2011,30(4)
采用文献法、录像解析法、访谈法等研究方法,以国家女子网球运动员为研究对象,对底线反手切削球关键技术动作进行三维录像和解析.结果表明:不同高度的来球其引拍和挥拍的动作不同,依据其动作特点可分为切削、平削和压削三种技术.分析发现:三种切削球技术动作在转体引拍和挥拍切削时的肩髋转动角、拍面角、身体倾斜角有显著差异;三种技术的挥拍动作均是由转体、拍臂依次加速的鞭打动作.以此研究揭示底线反手切削球技术的本质特征,为进一步提高网球教学和训练提供理论参考. 相似文献
10.
曾有一种说法认为,正手击球时非持拍手应指向球的方向。而如今,非持拍手对转体起着关键的辅助作用,而且还能够提高挥拍速度。因此,我们决不能忽视非持拍手的作用。 相似文献
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In this study, we wished to investigate the factors that determine the direction of the spin axis of a pitched baseball. Nineteen male baseball pitchers were recruited to pitch fastballs. The pitching motion was recorded with a three-dimensional motion analysis system (1000?Hz), and the orientations of the hand segment in a global coordinate system were calculated using Euler rotation angles. Reflective markers were attached to the ball, and the direction of the spin axis was calculated on the basis of their positional changes. The spin axis directions were significantly correlated with the orientations of the hand just before ball release. The ball is released from the fingertip and rotates on a plane that is formed by the palm and fingers; the spin axis of the ball is parallel to this plane. The lift force of the pitched baseball is largest when the angular and translational velocity vectors are mutually perpendicular. Furthermore, to increase the lift forces for the fastballs, the palm must face home plate. 相似文献
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William A. Edmonds Gershon Tenenbaum Derek T. Y. Mann Michael Johnson Akihito Kamata 《Journal of sports sciences》2013,31(7):761-773
Abstract In this study, we wished to investigate the factors that determine the direction of the spin axis of a pitched baseball. Nineteen male baseball pitchers were recruited to pitch fastballs. The pitching motion was recorded with a three-dimensional motion analysis system (1000 Hz), and the orientations of the hand segment in a global coordinate system were calculated using Euler rotation angles. Reflective markers were attached to the ball, and the direction of the spin axis was calculated on the basis of their positional changes. The spin axis directions were significantly correlated with the orientations of the hand just before ball release. The ball is released from the fingertip and rotates on a plane that is formed by the palm and fingers; the spin axis of the ball is parallel to this plane. The lift force of the pitched baseball is largest when the angular and translational velocity vectors are mutually perpendicular. Furthermore, to increase the lift forces for the fastballs, the palm must face home plate. 相似文献
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Direction of spin axis and spin rate of the pitched baseball 总被引：1，自引：0，他引：1
Jinji T Sakurai S 《Sports biomechanics / International Society of Biomechanics in Sports》2006,5(2):197-214
In this study, we aimed to determine the direction of the spin axis and the spin rate of pitched baseballs and to estimate the associated aerodynamic forces. In addition, the effects of the spin axis direction and spin rate on the trajectory of a pitched baseball were evaluated. The trajectories of baseballs pitched by both a pitcher and a pitching machine were recorded using four synchronized video cameras (60 Hz) and were analyzed using direct linear transform (DLT) procedures. A polynomial function using the least squares method was used to derive the time-displacement relationship of the ball coordinates during flight for each pitch. The baseball was filmed immediately after ball release using a high-speed video camera (250 Hz), and the direction of the spin axis and the spin rate (omega) were calculated based on the positional changes of the marks on the ball. The lift coefficient was correlated closely with omegasinalpha (r = 0.860), where alpha is the angle between the spin axis and the pitching direction. The term omegasinalpha represents the vertical component of the velocity vector. The lift force, which is a result of the Magnus effect occurring because of the rotation of the ball, acts perpendicularly to the axis of rotation. The Magnus effect was found to be greatest when the angular and translational velocity vectors were perpendicular to each other, and the break of the pitched baseball became smaller as the angle between these vectors approached 0 degrees. Balls delivered from a pitching machine broke more than actual pitcher's balls. It is necessary to consider the differences when we use pitching machines in batting practice. 相似文献
14.
Alexandra Atack Grant Trewartha Neil E. Bezodis 《Sports biomechanics / International Society of Biomechanics in Sports》2019,18(5):457-469
The appropriate determination of performance outcome is critical when appraising a performer’s technique. Previous studies of rugby place kicking technique have typically assessed performance based on ball velocity, but this is not the sole requirement. Therefore, a mathematical model of rugby place kick ball flight was developed to yield a single measure more representative of true performance. The model, which requires only initial ball flight kinematics, was calibrated and validated using empirical place kick data, and found to predict ball position with a mean error of 4.0% after 22 m of ball flight. The model was then applied to the performances of 33 place kickers. The predicted maximum distance, a single performance measure which accounted for initial ball velocity magnitude and direction, and spin, was determined using the model and was compared against ball velocity magnitude. A moderate association in the rank-order of the kicks between these two measures (ρ = 0.52) revealed that the relative success of the kicks would be assessed differently with each measure. The developed model provides a representative measure of place kick performance that is understandable for coaches, and can be used to predict changes in performance outcome under different ball launch or environmental conditions. 相似文献
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There has been significant technological advancement in the game of tennis over the past two decades. In particular, tennis
rackets have changed in size, shape and material composition. The effects of these changes on ball rebound speed have been
well documented, but few studies have considered the effects on ball angular velocity. The purpose of this study was to investigate
the effects of three factors on post-impact ball spin. Tennis balls were projected at three velocities toward a clamped racket
simulating three levels of stiffness and strung at three string tensions. The angular velocity of each tennis ball was measured
from stroboscopic images during an oblique impact with the racket. A three-way factorial ANOVA revealed significant (P < 0.01) differences in the post-impact angular velocity for string tension, racket stiffness and impact velocity, as well
as two-way interactions between string tension and impact velocity, and between racket stiffness and impact velocity. The
possibility of tangential elastic strain energy being stored in the racket and ball was evident in low impact velocity trials.
These displayed a post-impact angular velocity where the circumference of the ball was translating faster than the relative
velocity between the ball’s centre of mass and the string surface. It was concluded that increasing the relative impact velocity
between the racket and ball was the best means of increasing the post-impact angular velocity of the tennis ball. 相似文献
16.
ABSTRACT When executed correctly, swing bowling has the potential to influence the outcome of a cricket match, yet little is known about the required bowling action and ball flight characteristics. This study aimed to describe the bowling action and initial ball flight characteristics as well as to identify variables that may be associated with increased swing in pathway and high-performance medium and fast pace bowlers. A 17-camera Vicon motion analysis system captured retro-reflective markers placed on the upper-body of participants and new cricket balls to quantify bowling action and initial ball flight kinematics. Bowlers delivered the ball with their forearm and hand angled in the direction of intended swing with an extended wrist flexing through the point of ball release. Bowlers who produced more swing had increased seam stability, possibly linked to a lower wrist and ball angular velocity. It is believed that swing increases with seam stability, however, optimal ranges may exist for seam azimuth angle, ball angular velocity and release speed. These findings may assist coaches to optimise the performance of bowlers, however, future research should use bowlers who play at higher levels to investigate swing bowling at greater speeds. 相似文献
17.
Flight dynamics of the screw kick in rugby 总被引：1，自引：1，他引：0
This paper describes the aerodynamic forces and the flight trajectory for the screw (spiral) kick in rugby. The screw kick
is defined as that which causes the ball to spin on its longitudinal axis. The aerodynamic forces acting on a rugby ball spinning
on its longitudinal axis were measured in a wind tunnel using a six-component strut type balance. It was found that the drag,
the lift and the pitching moment depend on the angle of attack, while the side force (Magnus force) depends on both the spin
rate and the angle of attack in the range where the wind speed lies between 15 and 30 m s-1 and the spin rate is between 1 and 10 revolutions per second. Moreover, the flight trajectory was obtained by integrating
the full nonlinear six degrees of freedom equations of motion on the basis of aerodynamic data. In a simulation, a ball spinning
on its longitudinal axis tended to hook toward or away from the touchline even if the velocity and angular velocity vectors
were parallel to the touchline. The direction of the hook depends on the direction of the angular velocity vector. The initial
direction of the hook depends on the relationship between the flight path angle and the pitch angle as well as the direction
of the angular velocity vector. 相似文献
18.
Bruce Abernethy 《Journal of sports sciences》2013,31(1):17-34
The time of occurrence and spatial location of the advance cues used to anticipate the direction and force of an opponent's stroke in squash were examined using a film task. This task, designed to simulate the normal perceptual display of the defensive player, consisted of two discrete parts, each containing 160 individual stroke sequences (trials). In the first part of the film task, the display was occluded at different time intervals throughout the development of the opponent's stroke and the 16 expert and 20 novice subjects had to predict both the direction (down‐wall or cross‐court) and force (drive or drop shot) of the opponent's stroke. In the second part of the film task, visibility to selected advance cues was occluded by placing opaque mats on the film surface. Across all of the film task conditions experts were superior to novices in predicting the event outcome from the information available, highlighting the important contribution anticipatory skills make to expert performance in this sport. Analysis of lateral (direction) error showed that the most critical time periods for extracting information about stroke direction are the periods between 160–80 ms prior to racket‐ball contact and the period of extended ball flight arising at least 80 ms after contact. Whereas both groups were attuned to this ball flight information, only the experts were capable of picking up information from the early part of the opponent's actions. This early information appeared to be provided by the opposing player's arm action. Similar time periods were found to be also important for the prediction of stroke depth, but in this case both experts and novices were similar in their cue dependence. 相似文献
19.
A forward dynamics computer simulation for replicating tennis racket/ball impacts is described consisting of two rigid segments
coupled with two degrees of rotational freedom for the racket frame, nine equally spaced point masses connected by 24 visco-elastic
springs for the string-bed and a point mass visco-elastic ball model. The first and second modal responses both in and perpendicular
to the racket string-bed plane have been reproduced for two contrasting racket frames, each strung at a high and a low tension.
Ball/string-bed normal impact simulations of real impacts at nine locations on each string-bed and six different initial ball
velocities resulted in <3% RMS error in rebound velocity (over the 16–27 m/s range observed). The RMS difference between simulated
and measured oblique impact rebound angles across nine impact locations was 1°. Thus, careful measurement of ball and racket
characteristics to configure the model parameters enables researchers to accurately introduce ball impact at different locations
and subsequent modal response of the tennis racket to rigid body simulations of tennis strokes without punitive computational
cost. 相似文献
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Anticipation in squash: differences in advance cue utilization between expert and novice players 总被引：3，自引：0，他引：3
B Abernethy 《Journal of sports sciences》1990,8(1):17-34
The time of occurrence and spatial location of the advance cues used to anticipate the direction and force of an opponent's stroke in squash were examined using a film task. This task, designed to stimulate the normal perceptual display of the defensive player, consisted of two discrete parts, each containing 160 individual stroke sequences (trials). In the first part of the film task, the display was occluded at different time intervals throughout the development of the opponent's stroke and the 16 expert and 20 novice subjects had to predict both the direction (down-wall or cross-court) and force (drive or drop shot) of the opponent's stroke. In the second part of the film task, visibility to selected advance cues was occluded by placing opaque mats on the film surface. Across all of the film task conditions experts were superior to novices in predicting the event outcome from the information available, highlighting the important contribution anticipatory skills make to expert performance in this sport. Analysis of lateral (direction) error showed that the most critical time periods for extracting information about stroke direction are the periods between 160-80 ms prior to racket-ball contact and the period of extended ball flight arising at least 80 ms after contact. Whereas both groups were attuned to this ball flight information, only the experts were capable of picking up information from the early part of the opponent's actions. This early information appeared to be provided by the opposing player's arm action. Similar time periods were found to be also important for the prediction of stroke depth, but in this case both experts and novices were similar in their cue dependence. 相似文献