共查询到20条相似文献，搜索用时 31 毫秒
1.
This research reported here draws on self-organization theories and dynamical system models to investigate the collective behaviour of tennis players. In tennis, the unceasing to-and-fro displacements of a player about a “home” reference position, located in the middle of the baseline, are akin to those of an oscillator, and the reciprocal attending of both players establishes an informational linkage. Thus, theoretically, the displacement of the two players can be analysed as a system formed by two coupled non-linear oscillators. In such a system, relative phase has been shown to be an adept measure of the temporal synchronization between the oscillators. We hypothesized that relative phase is a relevant collective variable to characterize the relative motion of tennis players. Four players were videotaped and their displacements analysed. The results revealed just two stable patterns of synchronization, in-phase and anti-phase, as the players moved in the same or opposite directions, respectively. Moreover, relative phase showed two types of evolution within trials: either it remained stable at in-phase or anti-phase, or it exhibited transitions between these two modes. In accordance with our hypothesis, the results identified relative phase as a pertinent collective variable to represent both invariance and change in the relative displacements of tennis players. Such a finding opens new avenues for investigating dual sports. 相似文献
2.
In this study, we considered the interacting effects of expertise in gymnastics, the type of support surface and the required frequency of head movement on the emergence of postural modes of coordination. A group of elite female gymnasts and a control group of non-gymnasts were asked to track the fore-aft motion of a target with their heads. Two support surface conditions (a balance beam vs the floor) were crossed with four frequencies of target motion. The relative phase between the angular motion of the ankles and hips was analysed. Two stable patterns emerged: an in-phase mode and an anti-phase mode, with the hip-ankle relative phase close to 0 degrees and 180 degrees, respectively. Increasing target frequency produced a change from in-phase to anti-phase coordination, in conditions where no instructions were given to the participants (Experiment 1) as well as in those where participants were instructed to maintain an in-phase mode for as long as possible (Experiment 2). This change, however, occurred earlier for the non-gymnasts than for the gymnasts. We conclude that 0 degrees and 180 degrees are two stable postural coordination modes, that expertise in gymnastics leads to a functional modification of existing patterns of coordination, and that expertise in general can be considered an intrinsic constraint on coordination. 相似文献
3.
4.
5.
6.
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
7.
Claudia R. Juzwiak Maria S. S. Vitalle Marcelo M. Pinheiro Vera L. Szejnfeld 《Journal of sports sciences》2013,31(11):1209-1217
Abstract In this cross-sectional study, we evaluated the body composition and dietary intake of 44 adolescent tennis players. After being divided into two groups (age 10–13 years and age 14–18), the players had their weight, height, and sexual maturation assessed. Dual-energy X-ray absorptiometry was used to assess body composition. Food intake was obtained from a non-consecutive 4-day food record. The data were analysed using the Virtual Nutri v.1.0 software and compared with the present recommendations for adolescent athletes or dietary reference intakes. Body mass index and body fat for tennis practice were adequate for 89% and 71% of the tennis players respectively, regardless of age group. A calorie deficit greater than 10% of energy expenditure was observed in 32% of the sample. Fifty percent of the athletes consumed carbohydrates in accordance with recommended values. Protein and lipid intakes were above recommended values, while fibre, calcium, potassium, magnesium, and folic acid intakes were below recommendation for 98%, 80%, 100%, 100%, and 98% of the tennis players respectively. The observed nutritional deficiencies represent an additional barrier for adolescents engaged in competitive sports to achieve an optimum nutrition to maintain growth, health, and performance. 相似文献
8.
随着网球运动在中国飞速发展,网球运动的研究也成为体育领域中关注的论题。对网球运动员目标定向与归因方式的研究还比较缺乏。鉴于研究应用心理测量法对网球运动员的目标定向和归因方式进行探讨。了解中国网球运动员的目标定向及归因方式的现状,丰富运动员对目标定向和归因方式的认识。研究结果显示：网球运动员的目标定向在性别上存在显著性差异;网球运动员基本归因类型,在成功情境下为：内部的、稳定的、可控的;在失败情境下为：内部的、稳定的、不可控的;网球运动员在成功情境下的归因方式没有性别差异,在失败情境下内外源、稳定性存在性别差异;网球运动员的目标定向与归因方式的相关性不高,存在着低度相关。 相似文献
9.
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
10.
随着网球选手的击球更快更重,网球的比赛节奏也越来越快。比赛中选手们已经不仅仅是在比拼击球的质量,更是要比拼高强度的节奏中的稳定性,甚至是在被动,受迫情况下的回球成功率。要想拥有稳定的击球,就需要发展选手的体能与控制身体的能力。因此,训练选手在快速移动中的稳定平衡能力已经成为了当今网球研究的重要内容。通过对发展核心力量理论叙述以及对照分析在稳定和受迫情况下的击球形式来阐述发展核心力量对保证选手在快速移动中的动态平衡能力的重要性,为网球训练提供参考。 相似文献
11.
12.
Juzwiak CR Amancio OM Vitalle MS Pinheiro MM Szejnfeld VL 《Journal of sports sciences》2008,26(11):1209-1217
In this cross-sectional study, we evaluated the body composition and dietary intake of 44 adolescent tennis players. After being divided into two groups (age 10-13 years and age 14-18), the players had their weight, height, and sexual maturation assessed. Dual-energy X-ray absorptiometry was used to assess body composition. Food intake was obtained from a non-consecutive 4-day food record. The data were analysed using the Virtual Nutri v.1.0 software and compared with the present recommendations for adolescent athletes or dietary reference intakes. Body mass index and body fat for tennis practice were adequate for 89% and 71% of the tennis players respectively, regardless of age group. A calorie deficit greater than 10% of energy expenditure was observed in 32% of the sample. Fifty percent of the athletes consumed carbohydrates in accordance with recommended values. Protein and lipid intakes were above recommended values, while fibre, calcium, potassium, magnesium, and folic acid intakes were below recommendation for 98%, 80%, 100%, 100%, and 98% of the tennis players respectively. The observed nutritional deficiencies represent an additional barrier for adolescents engaged in competitive sports to achieve an optimum nutrition to maintain growth, health, and performance. 相似文献
13.
PT Esteves D Araújo K Davids L Vilar B Travassos C Esteves 《Journal of sports sciences》2012,30(12):1285-1293
Abstract In this study, we examined the effects of relative positioning of attacker-defender dyads to the basket on interpersonal coordination tendencies in basketball. To achieve this aim, four right-hand dominant basketball players performed in a 1 vs. 1 sub-phase, at nine different playing locations relative to the basket (from 0° to 180°, in 20° increments). Performers' movement displacement trajectories were video-recorded and digitized in 162 trials. Results showed that interpersonal coordination tendencies changed according to the scaling of the relative position of performers to the basket. Stable in-phase modes of coordination were observed between performers' longitudinal and lateral displacements (50.47% and 43.02%) on the left side of the court. On the right side of the court, a shift in the dominant mode of coordination was observed to a defender lead-lag of -30°, both for longitudinal and lateral displacements (30.51% and 32.65%). These results suggest how information about dribbler hand dominance and relative position to the basket may have constrained attacker-defender coordination tendencies in 1 vs. 1 sub-phases of basketball. 相似文献
14.
为评价世界精英男子网球运动员比赛表现特征,选取德约科维奇职业生涯2004至2016年间908场、穆雷职业生涯2005至2016年间804场单打比赛为研究对象。运用多元线性回归法对两位优秀网球选手竞技能力技战术指标特征进行分析,运用综合指数法对两人36场比赛对决进行综合评定。结果显示：（1）决定德约科维奇的比赛胜负指标由强到弱依次为二发得分率（0.915）、一发得分率（0.882）、挽救破发点成功率（0.749）、一发成功率（0.700）,决定穆雷的比赛胜负指标由强到弱依次为一发成功率（0.803）、二发得分率（0.675）、破发成功率（0.645）;（2）德约科维奇与穆雷10场大满贯比赛对决的综合指数平均值分别为3.997和3.862。研究表明：从整体上看,虽然两人职业对决在竞技状态上都有起伏,但并不存在显著性差异,且两人在比赛中均展现出一流的技战术水平。 相似文献
15.
João Carvalho Duarte Araújo Bruno Travassos Pedro Esteves Luís Pessanha Fernando Pereira 《Journal of sports sciences》2013,31(14):1596-1605
Abstract This study analysed how the relative positioning of players on court influenced patterns of interpersonal coordination in baseline rallies in tennis. We developed a model (PA index) that assigns a weight to the position of each player on court and determines a positional advantage, based on the relative proportionality between the lateral and longitudinal displacement values during rallies. To test the model, data from 27 randomly-selected baseline rallies from three ATP World Tour matches (professional tennis players' tournaments organized by Association of Tennis Professionals) on clay were analysed. Results revealed that the PA index of players on court described their interpersonal coordination dynamics during baseline rallies. It also identified the emergence of rally breaks in the interpersonal coordination patterns of competing dyads that led to a point being scored. Data suggest that positional advantage data may assist coaches in the design of training tasks to enhance players' court coverage and performance during competitive interactions, acting as a valuable tool for performance analysis in tennis. 相似文献
16.
对世界优秀乒乓球女双选手李恩实/石恩美的技战术分析与研究 总被引：2，自引：0，他引：2
李树清 《体育成人教育学刊》2004,20(5):78-79
世界优秀乒乓球女子双打选手李恩实／石恩美(韩国)近年来在世界大赛保持着较好的战绩，是中国乒乓球队女双的头号劲敌。通过对她们的发球、发球抢攻、接发球段和相持段的技、战术特点进行分析，以期为中国乒乓球女双备战国际大赛提供参考。 相似文献
17.
通过在乒乓球球拍的拍把上加装加速度传感器,并开发相应的击球力量训练数据实时采集系统,实时采集乒乓球运动员训练时挥拍的加速度数据,通过运动学和动力学分析,得出乒乓球运动员挥拍的速度、位移和力量等实时动态参数,并以曲线的形式实时、直观地显示给教练员和运动员,为教练员了解乒乓球运动员挥拍的力量等数据提供科学手段,为制订有针对性的技战术和体能训练计划提供科学依据。此外,采集的训练数据实时存储在后台数据库中,便于对运动员的击球力量等数据进行长期、科学的跟踪,以提高运动训练监控的针对性和科学化水平,提高乒乓球运动员的运动水平和比赛成绩 相似文献
18.
武汉市乒乓球运动学校经过多年的理论研究和实践工作,以＂女子技术男性化＂训练理念为指导,建立了一套行之有效的女子运动员培养模式,并于2008年和2010年分别为国家乒乓球女队输送了冯亚兰和易芳贤两名运动员。运用文献资料法、专家访谈法、逻辑分析法,对武汉市乒乓球运动学校女子运动员培养模式进行研究,为提高中国女子乒乓球后备力量成材率提供参考依据。 相似文献
19.
Pedro T. Esteves Duarte Araújo Keith Davids Luís Vilar Bruno Travassos Carlos Esteves 《Journal of sports sciences》2013,31(12):1285-1293
Abstract In this study, we examined the effects of relative positioning of attacker–defender dyads to the basket on interpersonal coordination tendencies in basketball. To achieve this aim, four right-hand dominant basketball players performed in a 1 vs. 1 sub-phase, at nine different playing locations relative to the basket (from 0° to 180°, in 20° increments). Performers’ movement displacement trajectories were video-recorded and digitized in 162 trials. Results showed that interpersonal coordination tendencies changed according to the scaling of the relative position of performers to the basket. Stable in-phase modes of coordination were observed between performers’ longitudinal and lateral displacements (50.47% and 43.02%) on the left side of the court. On the right side of the court, a shift in the dominant mode of coordination was observed to a defender lead-lag of ?30°, both for longitudinal and lateral displacements (30.51% and 32.65%). These results suggest how information about dribbler hand dominance and relative position to the basket may have constrained attacker–defender coordination tendencies in 1 vs. 1 sub-phases of basketball. 相似文献
20.
Perception of kinematic characteristics of tennis strokes for anticipating stroke type and direction
The purpose of this study was to determine the sources of visual information used by highly skilled tennis players in anticipating their opponent's shots. In Experiment 1, motion analysis of the strokes showed that the relative motion between the racquet and forearm was different between the ground strokes and lobs, but there were no reliable kinematic differences when shot direction was varied. In Experiment 2, 12 skilled tennis players observed the opponent hitting strokes in a normal video or in a point-light display with different segments occluded. Players' anticipation accuracy was not degraded by the use of the point-light display. Occluding the racquet and forearm significantly reduced the participant's ability to determine the type of stroke produced. 相似文献