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1.
The kinematics of the racket and ball near impact in tennis forehands were studied to document typical variation in successful and unsuccessful shots, in order to determine biomechanically meaningful differences in advanced players and confirm models of groundstroke trajectories. Seven tennis players (six males and one female) were videoed from the side at 180 Hz as they performed 40 forehand drives on an indoor tennis court. Vertical plane kinematics of the racket and ball near impact were analysed for sub samples of successful and unsuccessful shots for each subject. Most racket kinematic variables were very consistent (mean CV< 6.3%) for successful shots, so bio mechanically meaningful differences in angles and velocities of the racket and ball (3° and 2 m s−1) near impact could be detected between successful and unsuccessful shots. Four subjects tended to miss long and three subjects missed shots in the net that were reflected in initial ball trajectories. Mean (SD) initial trajectories for long shots were 9.8° (1.4°), while netted shots were 0.7° (1.1°) above the horizontal. The initial ball trajectories and margins for error for these subjects were smaller than those previously reported (Brody, 1987) because players tended to select mean ball trajectories close to one error than another, differing amounts of topspin, or incorrect lift and drag coefficients for tennis balls had not been published when this model was created. The present data can be used to confirm if recent models (Cookeet al., 2003; Dignallet al., 2004) more closely match actual performance by advanced players.  相似文献   

2.
This study sought to determine the features of an ideal serve in men’s professional tennis. A total of 25,680 first serves executed by 151 male tennis players during Australian Open competition were classified as either aces or returned into play. Spatiotemporal (impact location, speed, projection angles, landing location and relative player locations) and contextual (score) features of each serve were extracted from Hawk-Eye data and used to construct a classification tree model (with decision rules) that predicted serve outcome. k-means clustering was applied to the landing locations to quantify optimal landing locations for aces. The classification tree revealed that (1) serve directionality, relative to the returner; (2) the ball’s landing proximity to the nearest service box line and (3) serve speed classified aces with an accuracy of 87.02%. Hitting aces appeared more contingent on accuracy than speed, with serves directed >5.88° from the returner and landing <15.27 cm from a service box line most indicative of an ace. k-means clustering revealed four distinct locations (≈0.73 m wide × 2.35 m deep) in the corners of the service box that corresponded to aces. These landing locations provide empirically derived target locations for players to adhere to during practice and competition.  相似文献   

3.
目的:探索不同落点(T内角、Body追身和Wide外角)网球侧上旋发球技术动作的运动学规律。方法:采用2台三维高速摄像机拍摄10名网球运动员侧上旋发球技术动作,使用北京体育大学视讯解析系统采集运动学参数,对原始数据进行平滑和归一化处理等(Fc=10)。结果:1)抛球引拍阶段:抛球时左肩水平投影角呈显著性差异,左肩、右肩和左膝关节角速度变量呈显著性相关(R=0.82),站位方式无显著性差异;2)"挠背"阶段:不同落点发球时发力顺序协调一致,由下至上逐步将力量传递至击球点;3)挥拍击球阶段:击球时刻不同落点间分速度和击球角度差异性显著,外角侧旋>追身侧旋>内角侧旋,内角上旋>追身上旋>外角上旋,外角Angle>追身Angle>内角Angle。击球点高度与身高的倍数为外角(1.32)、追身(1.25)和内角(1.21),击球点由内至外逐渐向右偏移;4)随挥阶段:击球后重心位移和速度分量未出现显著性差异,膝关节角度变化均值39.7±1.8°。结论:我国高校网球二级运动员亟需储备发球隐蔽性、击球点空间位置、挥拍轨迹和击球速度分量等方面的意识体系。应当继续以运动生物力学为手段加强网球各类型发球技术动作、各环节运动特征和发球所致损伤因素等进行系统化和精细化研究。  相似文献   

4.
The influence of scaling court-size and net height on children’s tennis performance was examined. Sixteen boys (9.7 ± 0.5 years) had to perform a 30-min match in four different conditions, where court-size and/or net height were scaled by using a scaling ratio based on the differences in temporal demands between the children and the adult game. These 30-min matches were analysed using Tennis Analyst (FairPlay Ltd., Jindalee, QLD, Australia) software to determine typical tennis match performance characteristics. Children hit more winners, more forced errors, played more volleys, struck more shots from a comfortable height and played in a more forward court position when the net was scaled. Scaling both the court and net lead to a faster children’s game, more closely approximating what is typical of the adult game. The differences between the typical tennis performance variables recorded suggested that scaling the net led to a more aggressive way of playing. Further, children enjoyed playing on the standard court–scaled net condition more than standard adult conditions. It is suggested that optimising the scaling of net height may be as critical as other task constraints, such as racquet length or court-size, as it leads to a more engaging learning environment for experienced children.  相似文献   

5.
Tennis courts are normally classified as fast or slow depending on whether the coefficient of sliding friction (COF) between the ball and the surface is respectively small or large. This classification is based on the fact that the change in horizontal ball speed is directly proportional to the COF if the ball is incident at a small angle to the horizontal. At angles of incidence greater than about 16° it is commonly assumed that the ball will roll during the bounce, in which case one can show that the ratio of the horizontal speed after the bounce to that before the bounce will be 0.645 regardless of the angle of incidence or the speed of the court. Measurements are presented showing that (a) at high angles of incidence, tennis balls grip or ‘bite’ the court but they do not roll during the bounce, (b) the bounce:speed ratio can be as low as 0.4 on some courts and (c) the normal reaction force acts through a point ahead of the centre of mass. An interesting consequence is that, if court A is faster than court B at low angles of incidence, then A is not necessarily faster than B at high angles of incidence. An exception is a clay court which remains slow at all angles of incidence. The measurements also show that the coefficient of restitution for a tennis ball can be as high as 0.9 for an oblique bounce on a slow court, meaning that the ball bounces like a superball in the vertical direction and that slow courts are fast in the vertical direction.  相似文献   

6.
The primary aim of this study was to determine whether variations in rebound speed and accuracy of a tennis ball could be detected during game-simulated conditions when using three rackets strung with three string tensions. Tennis balls were projected from a ball machine towards participants who attempted to stroke the ball cross-court into the opposing singles court. The rebound speed of each impact was measured using a radar gun located behind the baseline of the court. An observer also recorded the number of balls landing in, long, wide and in the net. It was found that rebound speeds for males (110.1?±?10.2?km?·?h?1; mean?±?s) were slightly higher than those of females (103.6?±?8.6?km?·?h?1; P?<?0.05) and that low string tensions (180?N) produced greater rebound speeds (108.1?±?9.9?km?·?h?1) than high string tensions (280?N, 105.3?±?9.6?km?·?h?1; P?<?0.05). This finding is in line with laboratory results and theoretical predictions of other researchers. With respect to accuracy, the type of error made was significantly influenced by the string tension (P?<?0.05). This was particularly evident when considering whether the ball travelled long or landed in the net. High string tension was more likely to result in a net error, whereas low string tension was more likely to result in the ball travelling long. It was concluded that both gender and the string tension influence the speed and accuracy of the tennis ball.  相似文献   

7.
In tennis, a high ball velocity and a fast run toward the net are key features to successful performance of "serve-and-volley" players. For the serve, tennis players can use two techniques: the foot-up (FU) or foot-back (FB) technique. The aim of this study was to determine if the running time toward the net after the serve and the ball velocity (V(ball)) vary between these two techniques. Moreover we analysed the angular momentum values of the trunk and of the arm holding the racquet. Fifteen expert tennis players performed six successful serve-and-volleys with both techniques. Running time to the net is significantly lower for FB, whereas V(ball) is significantly higher for FU. Trunk and arm angular momentums about the transverse axis are significantly higher with FU before ball impact. A significant correlation (r = 0.81, P < 0.001) exists between changes in the maximal trunk angular momentum and in running time to the net between the two serve techniques. A significant correlation (r = 0.84, P < 0.001) also exists between changes in the maximal trunk angular momentum and in V(ball) between the two serve techniques. According to these results, FB is the best technique for moving as quickly as possible to the net because of a lower trunk angular momentum.  相似文献   

8.
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   

9.
运用数理统计为主的方法对男子网球单打运动员2011年ATP官网公布的十项技术统计与其年度积分进行主成份检验、相关性分析以及回归分析.研究显示:一发成功率,一发胜率,二发胜率,发球局胜率,挽救破发率五个技术统计是男子网球红土场的五个关键制胜因素.同时指出:红土场发球局的所有指标与接发球的所有指标呈负相关态势,上旋球,底线进攻以及良好的心理素质是红土场制胜的三个重要影响因素.  相似文献   

10.
Recreational tennis players tend to have higher incidence of tennis elbow, and this has been hypothesised to be related to one-handed backhand technique and off-centre ball impacts on the racket face. This study aimed to investigate for a range of participants the effect of off-longitudinal axis and off-lateral axis ball–racket impact locations on racket and forearm joint angle changes immediately following impact in one-handed tennis backhand groundstrokes. Three-dimensional racket and wrist angular kinematic data were recorded for 14 university tennis players each performing 30 “flat” one-handed backhand groundstrokes. Off-longitudinal axis ball–racket impact locations explained over 70% of the variation in racket rotation about the longitudinal axis and wrist flexion/extension angles during the 30 ms immediately following impact. Off-lateral axis ball–racket impact locations had a less clear cut influence on racket and forearm rotations. Specifically off-longitudinal impacts below the longitudinal axis forced the wrist into flexion for all participants with there being between 11° and 32° of forced wrist flexion for an off-longitudinal axis impact that was 1 ball diameter away from the midline. This study has confirmed that off-longitudinal impacts below the longitudinal axis contribute to forced wrist flexion and eccentric stretch of the wrist extensors and there can be large differences in the amount of forced wrist flexion from individual to individual and between strokes with different impact locations.  相似文献   

11.
The primary aim of this study was to determine whether variations in rebound speed and accuracy of a tennis ball could be detected during game-simulated conditions when using three rackets strung with three string tensions. Tennis balls were projected from a ball machine towards participants who attempted to stroke the ball cross-court into the opposing singles court. The rebound speed of each impact was measured using a radar gun located behind the baseline of the court. An observer also recorded the number of balls landing in, long, wide and in the net. It was found that rebound speeds for males (110.1+/-10.2 km.h-1; mean+/-s) were slightly higher than those of females (103.6+/-8.6 km.h-1; P<0.05) and that low string tensions (180 N) produced greater rebound speeds (108.1+/-9.9 km.h-1) than high string tensions (280 N, 105.3+/-9.6 km.h-1; P<0.05). This finding is in line with laboratory results and theoretical predictions of other researchers. With respect to accuracy, the type of error made was significantly influenced by the string tension (P<0.05). This was particularly evident when considering whether the ball travelled long or landed in the net. High string tension was more likely to result in a net error, whereas low string tension was more likely to result in the ball travelling long. It was concluded that both gender and the string tension influence the speed and accuracy of the tennis ball.  相似文献   

12.
对世界女子主流打法弧快类对阵弧快类和快弧类打法的比赛录像进行观察,研究接发球连胜两分的情况下接发球运动员对落点的控制、正反手使用率;在第一分得分的情况下,第二个接发球技战术.结果显示:女子接发球反手使用率高于正手,但不存在显著性差异;在先胜一分的情况下,第二个接发球得分中,接抢段得分率明显提高,且存在显著性差异;反手斜线配合反手斜线、反手直线配合正手直线等是比较常用且有效的路线配合方式.  相似文献   

13.
Whole body kinematics of the tennis serve have been reported extensively in the literature, yet comparatively less information exists regarding the kinematic characteristics of the swing and toss. In attempting to develop consistency in placement of the toss and racket trajectory, coaches will often decompose the serve and practice it in separate parts. A 22-camera VICON MX motion analysis system, operating at 250 Hz, captured racket, ball and hand kinematics of the serves of five elite junior players under three conditions. The conditions were flat first serves (FS) directed to a 1 × 1 m target bordering the ‘T’ of the deuce service box, a ball toss (BT) in isolation and a free swing (SW) in isolation. Players were instructed to perform BT and SW as in the FS. Paired t-tests assessed within-group differences in hand, racket and ball kinematics between the discrete skill and the two decomposed conditions. Vertical displacement of the ball at its zenith increased significantly during BT compared with the FS and temporal associations between racket and ball motion during the FS (r = 0.861) were affected during task decomposition. This study questions the pervasive use of task decomposition in the development of the tennis serve.  相似文献   

14.
The aim of this study was to compare the pre- and post-impact three-dimensional kinematics of the ball and racquet during first and second serves performed by elite tennis players. Data were collected from four male and four female right-handed professional players during competition using two high-speed cameras (200 Hz). For each player, one first serve and one second serve from the 'deuce' or right service court that landed within the specified target area were analysed. To test for significant differences between the first and second serves, Wilcoxon tests (P < or = 0.05) were performed on selected parameters. The results indicate that the ball travelled forward and to the left during the flight phase of the toss in all but one trial. The average pre-impact ball forward location for the first serve was significantly more in front and had a higher associated forward ball velocity than the corresponding values for the second serve. On average, the decrease in post-impact ball speed from the first to the second serve was 24.1%. No significant differences between the first and second serves were found in the pre-impact racquet head speed and orientation, which was represented as a unit vector perpendicular to the racquet face. The major adjustments made by the players when going from the first to second serve were a decrease in pre-impact ball forward location (P < or = 0.01) and an increase in the pre-impact racquet vertical and lateral velocities (both P < or = 0.05). This implies that the players tossed the ball closer to the body and imparted topspin and sidespin on the ball by changing the racquet vertical and lateral velocities when going from the first to the second serve.  相似文献   

15.
The serve, as the most important stroke in tennis, has attracted considerable biomechanical interest. Of its component parts, the swing has received disproportionate research attention and consequently, little is known regarding toss kinematics. Indeed, the age-old question of whether players serve to different parts of the court from the same toss remains unanswered. Six right-handed professionally ranked players hit first serves (FSs) and second serves (SSs) to three 2 x 1 m target areas reflecting the landing locations of T, body and wide serves, respectively, on the deuce court. A 22 camera, 250 Hz VICON MX motion analysis system captured racket, ball, foot, and h and kinematics. Repeated measures ANOVAs assessed within-player differences in foot, racket, and ball kinematics within the FS and SS as a function of landing location. The positions of the front foot, ball zenith, and ball impact were significantly different in the FS, while kinematics across all SS were consistent. Front foot position was closer to the centre mark in the T FS and players impacted the ball further left in the wide FS compared to the T FS. This study discusses the findings in the context of the development of the serve as well as potential implications for the return.  相似文献   

16.
Abstract

This study compared the amount of spin imparted to a tennis ball during impact with conventionally and diagonally strung tennis rackets. Balls were projected at the rackets at an angle of approximately 45°. The head of each racket was oriented vertically and clamped to eliminate any influence that deformations of the frame would have on the forces transmitted to the ball during impact. Ten multiple-image photographs (five using a relatively slow ball velocity and five using a relatively fast ball velocity) were taken of a ball approaching, striking, and leaving the rackets.

For similar pre-impact conditions, it was found that the angular impulse of the contact force applied to the ball (and hence the amount of spin) was almost identical for the two string configurations. Possible explanations of this finding are discussed.  相似文献   

17.
The serve is considered amongst the most important strokes in tennis. Not surprisingly, the development of a mechanically consistent and proficient serve is paramount. Correspondingly, drills that involve players serving with their eyes closed are thought to promote mechanical consistency. The purpose of this study was therefore to contrast the effect of the removal of visual feedback on ball and racket kinematics in the serve. A 10-camera 500-Hz VICON MX motion analysis system recorded the service actions of eight elite young players as they performed three serves with eyes open and three serves with eyes closed. Removal of vision resulted in considerable differences in both racket and ball kinematics, with players failing to make contact on 16 of 24 serves. Temporally, the preparation phase was significantly shorter with eyes closed. Spatially, the ball was located 6.5 cm further to the right at zenith, and 13 cm higher at impact with eyes closed. These results highlight that the serve is not entirely pre-programmable, and that visual feedback is critical to the spatiotemporal regulation of the serve. In turn, coaches need to be aware of the implications of modifying visual feedback in serve, and ensure that the consequence is congruent with their intent.  相似文献   

18.
Purpose: The net height in tennis (0.91 m) is approximately 50% of a professional tennis player’s height. Children are also expected to play with this net height, even though it is approximately 70% of the average 10-year-old’s height. This study examined the immediate effect of lowering net height on the performance characteristics of skilled junior tennis players aged 10 years and younger. Method: Sixteen players were matched in 8 pairs of even tennis ability and same sex. Each pair played 25-min singles matches in 4 conditions that varied in net height (0.91 m, 0.78 m, 0.65 m, and 0.52 m). Match-play characteristics were analyzed via video replay. Results: Results showed that lowering the net height to 0.65 m and 0.52 m led to players adopting a more attacking style of play, as evidenced by a significant increase in the number of winners without a commensurate increase in errors and more shots struck inside the baseline. Lower nets also led to a greater percentage of successful first serves. The lowest net (0.52 m), however, reduced rally length significantly and therefore decreased hitting opportunities. Conclusion: These results offer support for equipment scaling to enhance match-play performance for skilled junior tennis players. We propose that current net height recommendations for junior tennis should be revised.  相似文献   

19.
Enhancing the understanding of coordination and variability in the tennis serve may be of interest to coaches as they work with players to improve performance. The current study examined coordinated joint rotations and variability in the lower limbs, trunk, serving arm and ball location in the elite female tennis serve. Pre-pubescent, pubescent and adult players performed maximal effort flat serves while a 22-camera 500 Hz motion analysis system captured three-dimensional body kinematics. Coordinated joint rotations in the lower limbs and trunk appeared most consistent at the time players left the ground, suggesting that they coordinate the proximal elements of the kinematic chain to ensure that they leave the ground at a consistent time, in a consistent posture. Variability in the two degrees of freedom at the elbow became significantly greater closer to impact in adults, possibly illustrating the mechanical adjustments (compensation) these players employed to manage the changing impact location from serve to serve. Despite the variable ball toss, the temporal composition of the serve was highly consistent and supports previous assertions that players use the location of the ball to regulate their movement. Future work should consider these associations in other populations, while coaches may use the current findings to improve female serve performance.  相似文献   

20.
The purpose of this article was to examine the effect of equipment scaling, through the modification of tennis ball compression, on elite junior tennis players (aged 10 years) within a match-play context. The two types of ball compressions that were compared were the standard compression (the normal ball) and 75% compression (termed the modified ball). Ten boys and 10 girls participated in the study. Participants were stratified into pairs based on their Australian Age Ranking and gender. Each pair played two two-set matches: one match with standard compression balls and one match with modified balls. The characteristics of each match were analysed and compared. The results showed that the use of the modified ball increased rally speed, allowed players to strike the ball at a lower (more comfortable) height on their groundstrokes and increased the number of balls played at the net. Ball compression had no effect on the relative number of winners, forehands, backhands, first serves in and double faults. The results are discussed in relation to skill acquisition for skilled junior tennis players.  相似文献   

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