A kinematic comparison between long-line and cross-court top spin forehand in competitive table tennis players

ABSTRACT

The aim of the present study was to compare the biomechanical characteristics of the table tennis top spin shot when played cross-court (CC) or long-line (LL) in competitive table tennis players. Seven national level players respectively completed 10 long-line and 10 cross-court top spin shots responding to a standard ball machine. A stereophotogrammetric system was used to track body segments while executing the motion. Significantly more flexed right knee and elbow angles were measured at the moment of maximum velocity of the racket (MMV) in LL. In addition, significantly greater angles between the feet and the table and between the shoulders and the table at the MMV, indicated more pronounced rotation angles of the lower upper and upper-body in LL compared to CC with respect to the table. A higher inclination of the racket at the MMV was found in LL. The elbow flexion and the racket inclination may be associated to the direction of the shot. The present findings show that kinematic differences exist between the LL and the CC topspin forehand in competitive table tennis players. Coaches should be aware of these differences to adopt the optimal teaching strategies and to reproduce proper joint angles during training.     

Kinematics of table tennis topspin forehands: effects of performance level and ball spin

Abstract

The purpose of this study was to investigate whether performance level and ball spin affect arm and racket kinematics of the table tennis topspin forehand. Nine advanced and eight intermediate male table tennis players hit topspin forehands against light and heavy backspins. Five high-speed video cameras were used to record their strokes at 200 fps. Contributions of joint rotations to the racket speed, the racket kinematics at ball impact, the time required for racket acceleration and the maximum slope of the racket speed-time curve (s _max) were determined. The advanced players showed a significantly larger contribution of lower trunk axial rotation to the racket speed at impact and a significantly larger value of s_max, and tended to require a less time for racket acceleration than the intermediate players. The racket speed at impact was not significantly different between the two player groups. The players adjusted the racket face angle rather than the inclination of the racket path at impact to the different ball spins. The results suggest that the ability to accelerate the racket in less time in the topspin forehand against backspin balls may be an important factor that affects the performance level.     

Effect of skill decomposition on racket and ball kinematics of the elite junior tennis serve

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.     

Differences in ball speed and accuracy of tennis groundstrokes between elite and high-performance players

Abstract

The main aim of this study was to identify and compare ball speed and hitting accuracy of forehand and backhand groundstrokes between ATP professionals (elite) and high-performance youth players when shots were played cross-court and down the line to a target square. Six elite and seven high-performance tennis players volunteered to participate in the study. A Doppler-radar device and a digital video camera, operating at 120 frames per second, were used to measure ball speed and accuracy of forehand and backhand groundstrokes in the respective situation (cross-court and down the line). The results of 1040 measured groundstrokes indicate that the ball speed of the forehand and the backhand ground stroke was higher in the elite group when analysing (1) all valid shots, (2) the six fastest shots, and (3) the six most accurate shots (all P < 0.05). In addition, all players achieved a higher forehand speed compared with their backhand when balls were directed cross-court (P < 0.01). The participants demonstrated similar ability when considering accuracy of their groundstrokes (P > 0.05). However, a group difference for accuracy was identified when considering the six fastest forehand shots (P<0.05), and the forehand cross-court stroke was played more accurately than the backhand cross-court stroke by both groups (valid shots and six most accurate shots, P<0.05). Moreover, there was no evidence that players who impacted the ball faster were any less accurate than those who impacted the ball more slowly. Analyses for participants actually revealed a negative correlation between ball speed and mean radial error (accuracy) for the backhand down the line (r= ? 0.77, P<0.01). According to the results of this study, ball speed seems to be the determining factor that separates elite from sub-elite tennis players.     

Effect of swim speed on leg-to-arm coordination in unilateral arm amputee front crawl swimmers

The aim of this study was to examine the effect of swimming speed on leg-to-arm coordination in competitive unilateral arm amputee front crawl swimmers. Thirteen well-trained swimmers were videotaped underwater during three 25-m front crawl trials (400 m, 100 m and 50 m pace). The number, duration and timing of leg kicks in relation to arm stroke phases were identified by video analysis. Within the group, a six-beat kick was predominantly used (n = 10) although some swimmers used a four-beat (n = 2) or eight-beat kick (n = 1). Swimming speed had no significant effect on the relative duration of arm stroke and leg kick phases. At all speeds, arm stroke phases were significantly different (P < 0.05) between the affected and unaffected sides. In contrast, the kicking phases of both legs were not different. Consequently, leg-to-arm coordination was asymmetrical. The instant when the leg kicks ended on the affected side corresponded with particular positions of the unaffected arm, but not with the same positions of the affected arm. In conclusion, the ability to dissociate the movements of the arms from the legs demonstrates that, because of their physical impairment, unilateral arm amputee swimmers functionally adapt their motor organisation to swim front crawl.     

Time-out! How psychological momentum builds up and breaks down in table tennis

ABSTRACT

The current study examined the development of psychological momentum (PM) in table tennis and the effect of a time-out. Eighty table tennis players were exposed to an audiovisual scenario, in which they either came back from 1–7 to 7–7 in an all-decisive game (positive momentum), or in which the opponent came back from 7–1 to 7–7 (negative momentum). Furthermore, at the score of 7–7 a time-out was called. One group of participants received no specific instructions during the time-out, whereas the other group received task (mastery-approach – MAp) instructions. Overall, PM perceptions increased for participants in the positive momentum condition, but decreased rapidly for participants in the negative momentum condition. In addition, the time-out led to a loss of PM in the positive momentum condition, but to a recovery of PM in the negative momentum condition. The instructions during the time-out did not make a significant difference. Together, these results suggest that scoring patterns in a table tennis game significantly affect the PM of players. Furthermore, a player or coach could benefit from calling a time-out in a negative momentum situation, as this provides an opportunity to psychologically recover.     

Physiological demands of match-play in elite tennis: A case study

Abstract

The physiological and perceptual demands together with match notation of a four-set tennis match were studied in two elite professional players during the preparation for the 2008 Davis Cup. The design of this case report is unique in that it is the first to describe the demands of prolonged match-play (197 min) over four sets in ecologically valid conditions. The variables measured before and after each set included blood lactate and glucose concentrations, body mass, and perception of effort. Stroke count for each rally and heart rate were recorded during each set while salivary cortisol concentration was determined before and after the match. The rally length decreased as the match progressed. The results showed significant physiological stress, with each player losing greater than 2.5% of body mass (as fluid) and having elevated salivary cortisol concentrations after the match. Heart rate and perception of effort were also increased following each set indicating increasing stress. However, blood lactate decreased following the fourth set while blood glucose was maintained. The results also suggest that elite players may adjust work rates or tactics to cope with the increased perception of effort. This report shows that four sets of tennis are associated with increasing stress and fatigue.     

Elite tennis player sensitivity to changes in string tension and the effect on resulting ball dynamics

Eighteen elite male tennis players were tested to determine their ability to identify string tension differences between rackets strung from 210 N (47 lb) to 285 N (64 lb). Each player impacted four tennis balls projected from a ball machine before changing rackets and repeating the test. Eleven participants (61%) could not correctly detect a 75 N (17 lb) difference between rackets. Only two participants (11%) could correctly detect a 25 N (6 lb) difference. To establish whether varying string tensions affected ball rebound dynamics, the ball’s rebound speed and landing position were analysed. The mean rebound ball speed was 117 km h⁻¹, with only the trials from the 210 N racket producing significantly lower (P < 0.05) rebound speeds than the 235 N and 260 N rackets. This is contrary to previous laboratory-based tests where higher rebound speeds are typically associated with low-string tensions. The anomaly may be attributable to lower swing speeds from participants as they were not familiar with such a low string tension. Ball placement did not appear related to string tension, with the exception of more long errors for the 235 N racket and fewer long errors for the 285 N racket. It was concluded that elite male tennis players display limited ability to detect changes in string tension, impact the ball approximately 6% faster than advanced recreational tennis players during a typical rallying stroke, and that ball placement is predominantly unrelated to string tension for elite performers.     

沈阳体育学院乒乓球专修学生运动损伤情况调查

目的:研究乒乓球运动员损伤部位、类型、原因、损伤治疗情况,提出减少和预防乒乓球运动损伤的措施和建议.方法:采用观察法、问卷调查法、文献资料法对沈阳体育学院乒乓球院队及运动训练系专修共52名学生的运动损伤进行研究.结果:乒乓球专修学生以慢性损伤为主占34.62％,以肌肉损伤为主占36.54％,其中腰背部肌肉损伤最多占22.47％;在损伤部位方面,肩关节最多占29.9％,不同的技术特点会引起不同部位和不同性质的损伤;损伤治疗以外敷药为主.     

Effect of the racket mass and the rate of strokes on kinematics and kinetics in the table tennis topspin backhand

The purpose of this study was to investigate the effect of the racket mass and the rate of strokes on the kinematics and kinetics of the trunk and the racket arm in the table tennis topspin backhand. Eight male Division I collegiate table tennis players hit topspin backhands against topspin balls projected at 75 balls · min^?1 and 35 balls · min^?1 using three rackets varying in mass of 153.5, 176 and 201.5 g. A motion capture system was used to obtain trunk and racket arm motion data. The joint torques of the racket arm were determined using inverse dynamics. The racket mass did not significantly affect all the trunk and racket arm kinematics and kinetics examined except for the wrist dorsiflexion torque, which was significantly larger for the large mass racket than for the small mass racket. The racket speed at impact was significantly lower for the high ball frequency than for the low ball frequency. This was probably because pelvis and upper trunk axial rotations tended to be more restricted for the high ball frequency. The result highlights one of the advantages of playing close to the table and making the rally speed fast.     

对新型乒乓球性能的计算与研究

据国际乒联透露,为提高乒乓球的观赏性,吸引群众,将把现用乒乓球的直径由３８毫米改为４０毫米,被称为“新型球”或“大球”,并将在１９９７年第４４届世乒赛期间举行一次实验性的大球比赛。为了解大球的性能,探索其可行性,以尽快掌握其运动规律,对大球的参数和性能进行了计算与分析。如果制作大球的材料与小球的相同,计算结果：大球的质量增加０．２７１７克,材料体积增加０．１８８４厘米３,球的体积增大４．７８１厘米３,绕通过质心额状轴为转动惯量增加１．３９１立方厘米。如果用大球比赛,以与击小球同样的方式和大小相等的力来打击大球,大球的转速将比小球减少９．４１转／秒（约减少１／５）,速度减慢４．１４米／秒（约减少１／１０）,但大球的性能发生了明显的变化。     

Effectiveness of physical education to promote motor competence in primary school children

Background: Motor skill (MS) competence is an important contributing factor for healthy development.

Purpose: The goal was to test the effectiveness of primary school physical education (PE) on MS and physical fitness (PF) development.

Methods: Three classes (n?=?60, aged 9.0?±?0.9) were randomly assigned to three diverse conditions during a school year: two PE lessons/week (PE-2), three PE lessons/week (PE-3), and no PE lessons control group (CG). BMI, skinfolds, PF (9-min run/walk, sit-up, modified pull-ups), gymnastics, soccer, handball, basketball and track-and-field skills were evaluated. Effect sizes (d) were reported as magnitude of change.

Results: Skinfolds significantly increased only in CG (d?=?1.21). PF composite z-scores improved in PE-3 (d?=?0.61), but decreased in PE-2 (d?=?0.57), and had no changes in CG. Statistically significant improvement was verified in gymnastics and handball skills in both experimental groups (gymnastic: d?=?2.95 and d?=?2.61 for PE-3 and PE-2, respectively; handball: d?=?1.87 and d?=?0.57 for PE-3 and PE-2, respectively), and no changes were seen in CG. In soccer, there were improvements only in the PE-3 (d?=?0.55), and in basketball only in PE-2 (d?=?0.46). There were no changes in any group for track-and-field skills.

Conclusions: PE programs can effectively promote PF and MS development.     

直拍横打技术对广东高校乒乓球教学的启示

通过对第49届世界乒乓球锦标赛团体赛马琳对柳承敏的录像分析,发现双方均是直拍快攻型选手,而马琳反手是推挡加横打型,柳承敏反手是推挡加攻球型,马琳的直拍横打优于柳承敏的反手推挡,直拍横打解决了直拍运动员反手攻击力不强的问题,直拍近台快攻打法有强大的生命力。结合广东部分高校体育专业乒乓球班学生与普通系乒乓球班学生的现状进行分析,访谈了广东高校一些乒乓球教师,结果表明,广东高校乒乓球直拍横打的发展比较滞后,应该在乒乓球教学中采取措施开展直拍横打,方能使乒乓球的群众性运动进一步发展。     

Effects of bilateral and non-dominant practices on the lateral preference in judo matches

This study analysed the effects of bilateral and non-dominant practice on novice practitioners’ lateral preference for judo skills in a combat context (i.e., randori). Thirty sports sciences students (22 men and 8 women; mean age 19 ± 1 years) with right hand, foot, and counterclockwise rotation preferences were divided into 3 groups: bilateral (BG; n = 8), non-dominant (NDG; n = 11), and control (CG; n = 11). Participants received 8 weeks of training at a rate of 3 days per week. The NDG was trained to perform judo skills exclusive with their non-dominant side, while the BG performed every task symmetrically. Before and after training, participants were recorded during two 3-min randoris to obtain the percentage of their engagement in dominant side actions. Pretest percentages were 73.1 ± 19.9%, 77.8 ± 18.8%, and 68.9 ± 27.2% for BG, NDG, and CG, respectively. Post-test values were 75.0 ± 15.6%, 23.3 ± 27.9%, and 72.2.9 ± 20.4%, respectively. Significant differences were observed between NDG and each of the other groups after the training. Changes from pretest were only significant for NDG (P = 0.003). These results suggest that lateral preference among novice judo practitioners during randori can be modulated by the type of practice.     

速滑运动员运动性心理疲劳的产生与对策

从训练角度出发,针对速滑项目特点,运用运动心理学相关知识,分析速滑运动员运动性心理疲劳产生的原因、表现和影响,提出解决问题的有效途径与对策,旨在帮助速滑教练员提高对运动员的心理训练的重视程度,通过有效的方法解决运动员心理疲劳问题,从而提高运动员的成绩。     

Mechanical energy generation and transfer in the racket arm during table tennis topspin backhands

The ability to generate a high racket speed and a large amount of racket kinetic energy on impact is important for table tennis players. The purpose of this study was to understand how mechanical energy is generated and transferred in the racket arm during table tennis backhands. Ten male advanced right-handed table tennis players hit topspin backhands against pre-impact topspin and backspin balls. The joint kinetics at the shoulder, elbow and wrist of the racket arm was determined using inverse dynamics. A majority of the mechanical energy of the racket arm acquired during forward swing (65 and 77% against topspin and backspin, respectively) was due to energy transfer from the trunk. Energy transfer by the shoulder joint force in the vertical direction was the largest contributor to the mechanical energy of the racket arm against both spins and was greater against backspin than against topspin (34 and 28%, respectively). The shoulder joint force directed to the right, which peaked just before impact, transferred additional energy to the racket. Our results suggest that the upward thrust of the shoulder and the late timing of the axial rotation of the upper trunk are important for an effective topspin backhand.     

中医药与运动性疲劳的研究现状及展望

从中医理论的整体观念出发,对中医药理论在应用防治运动性疲劳的研究方面进行分析和综述,并提出存在的问题及改进建议。     

运动中疲劳与心理耗竭若干问题研究述评

运动中的疲劳和心理耗竭是复杂的应激反应过程.运动疲劳的研究经历了由生理学取向向生理心理社会学取向的过程,其产生的主要原因在于环境因素、行为因素和动机因素等.对认知-情意模式、训练压力反应模式等几种理论进行了描述,对运动与心理耗竭的关系进行了探讨,并提出了今后研究的方向.     

Coordination and variability in the elite female tennis serve

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.     

高水平运动技能训练中的运动知觉心理训练取向

针对目前高水平运动技能训练中解决细节问题时缺乏具体操作方法的现状,试图通过基础理论及运动专门化知觉训练范式的分析,以引起教练员对运动技能心理训练的重视。研究提出,应该重视心理训练在运动技能训练中的作用,心理训练不仅仅只是情绪管理,它还担负增强动作技能认知复述的任务;正确的运动知觉是运动反应的前提,专门化知觉训练是运动技能训练方法的取向;高水平运动技能训练中求质比求量更重要,破坏动力定型或认知结构的练习宁肯不做;建立科学的感知觉定位系统并结合有效反馈控制手段是操作策略;遮蔽、表象、反馈和量化控制等是技能细化的具体方法。