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.     

Biomechanical analysis of knee and trunk in badminton players with and without knee pain during backhand diagonal lunges

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.     

Glenohumeral contact force during flat and topspin tennis forehand drives

The primary role of the shoulder joint in tennis forehand drive is at the expense of the loadings undergone by this joint. Nevertheless, few studies investigated glenohumeral (GH) contact forces during forehand drives. The aim of this study was to investigate GH compressive and shearing forces during the flat and topspin forehand drives in advanced tennis players. 3D kinematics of flat and topspin forehand drives of 11 advanced tennis players were recorded. The Delft Shoulder and Elbow musculoskeletal model was implemented to assess the magnitude and orientation of GH contact forces during the forehand drives. The results showed no differences in magnitude and orientation of GH contact forces between the flat and topspin forehand drives. The estimated maximal GH contact force during the forward swing phase was 3573 ± 1383 N, which was on average 1.25 times greater than during the follow-through phase, and 5.8 times greater than during the backswing phase. Regardless the phase of the forehand drive, GH contact forces pointed towards the anterior-superior part of the glenoid therefore standing for shearing forces. Knowledge of GH contact forces during real sport tasks performed at high velocity may improve the understanding of various sport-specific adaptations and causative factors for shoulder problems.     

The development of skill and tactical competencies during a season of badminton

Abstract

In this study, we examined the development of skill competence and tactical knowledge of 41 eighth-grade students (mean age 13.6 years) as they completed a season of badminton conducted following the features of Sport Education. Using data from students’ performance on badminton skills tests, their competence in game play, and their tactical knowledge, it was determined that these students made significant improvements in their ability to not only control the shuttle, but also to hit it more aggressively. This resulted in improvements in both the selection (what shot to make) and execution (ability to produce the desired shot) dimensions of their game play. In addition, the students demonstrated significant improvements in their ability to select tactical solutions and make arguments for those decisions when watching videotaped performances of badminton games. The key explanation for the development of competence in this setting was that the structure of the Sport Education season allowed for significant practice opportunities, and that the authenticity and consequential nature of the game play helped move all but weak novice students from a more cooperative version of net-game play to one where tactical decision making and execution was valued.     

残疾儿童体育游戏的设计与教学

残疾儿童体育游戏设计应贯彻玩耍、基础动作为主、全纳教育的理念，以提高健康为目标。其设计过程中应注意趣味性、自由性、竞争性、可变性、简易性。     

全运会与全国体育大会特点之比较

全国体育大会是与全运会、城运会并列的全国性综合大型体育赛事,全运会是与奥运会接轨的发展我国竞技体育的最高组织形式,而全国体育大会则是把非奥运项目吸纳进来,推动全民健身发展的全国综合性运动会。虽然二者都是全国性运动会,但它们之间却有很多不同之处,把握两者之间的异同点,为解决竞技体育与群众体育发展之间的矛盾,迈向体育强国提供理论参考。     

Differences in trunk and upper extremity kinematics and segmental velocities during the offside forehand polo swing between male and female athletes

ABSTRACT

Although polo is a well-known equestrian sport, it is fundamentally misunderstood. The purpose of this study was to examine trunk and upper extremity kinematics and segmental velocities during the offside forehand polo swing between male and female athletes. Ten female and 17 male professional polo athletes volunteered. An electromagnetic tracking system collected kinematic data at 100 Hz while participants performed three offside forehand polo swings from a stationary wooden horse. One-way ANOVAs revealed statistically significant differences (p<0.05) in all kinematic variables and segmental velocities. Specifically, males exhibited a greater mean difference (MD=23°) of trunk flexion at take away (TA) and top of backswing (TOB)(MD=29°) trunk lateral flexion at ball contact (BC)(MD=23°), trunk rotation at TA(MD=97°) and TOB(MD=118°), shoulder abduction at TOB(MD=64°), and shoulder elevation at TOB(MD=13°) and BC(MD=40°). Females displayed greater trunk rotation at BC(MD=91°), shoulder elevation at TA(MD=19°), and elbow flexion at TA(MD=90°). Additionally, females generated greater segmental velocities early in the swing, while the males generated velocity later. The movement patterns observed amongst the males suggest energy is being transferred more efficiently along the kinetic chain, thus more efficient swing mechanics, but further investigation into the role of the trunk and lumbopelvic-hip complex in reference to the polo swing is warranted.     

男子散打运动员赛前降体重对运动能力和体液离子的影响

以6名上海优秀男子散打运动员为研究对象,对赛前体重控制、运动能力和体液离子变化情况进行研究,每周3次体脂率测试;每2周测试1次无氧运动能力和体液离子情况。结果显示,第3周体重和体脂率显著下降(P<0.05),第5周体重发生高度显著变化(P<0.01),体脂率和瘦体重显著下降(P<0.05);无氧运动能力在整个控重过程无显著变化(P>0.05);第3周Na+升高非常显著(P<0.01),Ca2+显著升高(P<0.05),CO2CP下降(P<0.05),第5周Na+浓度有所下降但仍高于控重前(P<0.05),Ca2+显著升高(P<0.05),CO2CP明显下降(P<0.01)。研究表明通过延长整理活动和增加有氧训练课可以实现运动员控重以消耗脂肪为主的目标,能够保证运动员无氧能力不损失,通过电解质饮料补充能够维持队员机体内环境的稳定。     

预防慢性疾病发生、发展的最佳身体活动负荷研究综述

从身体活动对慢性疾病预防和控制功效的视角,从身体活动对不同年龄群体的生理退化速率、死亡率、疾病发生率、心血管疾病、糖尿病、癌症、骨质疏松症、心理健康的影响等方面对国外相关研究进行梳理,对国外身体活动负荷标准的研究进行归纳,重点分类归纳了预防慢性疾病发生的成年人(18～65岁)、老年人(65岁以上)和已患慢性疾病群体控制疾病发展的不同群体间身体活动的适宜负荷方式和剂量,对身体活动与慢性疾病的研究做出了展望。     

乒乓球、羽毛球女子运动员与普通女大学生优劣肢及体成分的比较

乒乓球、羽毛球项目的运动技术特点会造成运动员自身优秀肢体的差异，本实验选北京体育大学运动系7名小球项目女运动员（实验组）和7名普通女大学生（对照组）来进行部分身体形态的分析，结论是实验组优劣肢的握力，上臂紧张围等指标存在着明显差异，对照组左右肢均衡，实验组省势肢与对照组左肢的握力，上臂放松围等指标存在着差异，其他各项指标上并无明显差异。     

Focusing of visual attention at rest and during physical exercise in soccer players

Abstract

In this study, we investigated the focus of visual attention in expert soccer players together with the effects of acute bouts of physical exercise on performance. In two discriminative reaction time experiments, which were performed both at rest and under submaximal physical workload, visual attention was cued by means of spatial cues of different size followed by compound stimuli with local and global target features. Soccer players were slower than non-athletes in reacting to local compared with global targets, but were faster in switching from local to global attending. Thus, soccer players appear to be less skilled in local attending, but better able than non-athletes to rapidly “zoom out” the focus of attention. Non-athletes generally showed faster performance under physical load, as expected according to the hypothesis of exercise-induced increases in arousal and/or activation and in resource allocation. In contrast, soccer players showed a more differentiated pattern of exercise-induced facilitation that selectively affects specific components of the attentional performance and is interpreted by referring to the role played by individual expertise and cognitive effort.     

高校领导对学校体育工作的认识和参与活动的情况

依据社会学原理,就普通高等院校开展学校体育工作的现状及发挥学校体育方面的优势服务于全民健身战略,对校级领导进行调查研究,为进一步推动学校体育工作的改革提供参考依据.     

科学体育在全民健身中的作用

通过对科学体育的分析研究,论述了全民健身活动的理论基础,探讨了“运动处方”和“运动负荷价值阈”在全民健身活动中的作用和运用方法。     

全国足球甲级联赛期间部分足球运动员赛中重度损伤的原因及预防措施

对足球甲级联赛赛中重度损伤的成因进行追踪，通过对部分损伤实例的报道及对其机制的分析发现：加强足球运动员全面身体素质的平衡发展及技术动作的合理应用，开展对运动员的职业道德和文明精神教育，提高球队医务人员的业务素质和专业技术水平是防止足球运动员重度损伤的重要因素。     

西方学校体育思想基础对我国学校体育思想基础建构的启示

从近现代中国学校体育向西方学习借鉴中存在的问题入手,分析了学习借鉴难于自洽并达到理想效果的根本原因是我国学习借鉴西方学校体育思想重视其形而未得其神,理论背后缺乏统一的和谐的学校体育内在思想基础。对西方学校体育影响较大的三大思想基础进行了归纳;提出了建构我国学校体育思想应注重思想基础的建设,并提出了构建过程中应重点关注的问题。     

河南省城市弱势群体的体质状况调研及生活习惯与运动行为分析

城市弱势群体的体质状况不容乐观，该群体在饮食理念、科学膳食方面整体表现不佳。弱势群体的体育活动是全民健身计划的一部分。对这一特殊群体的体育活动予以理论上的指导和行动上的支持，要倡导克服不良生活习惯和不良嗜好，杜绝恶习、陋习，保持良好心态，促进身心健康。     

Major League Baseball pace-of-play rules and their influence on predicted muscle fatigue during simulated baseball games

Major League Baseball (MLB) has proposed rule changes to speed up baseball games. Reducing the time between pitches may impair recovery from fatigue. Fatigue is a known precursor to injury and may jeopardise joint stability. This study examined how fatigue accumulated during baseball games and how different pace of play initiatives may influence fatigue. Pitcher data were retrieved from a public database. A predictive model of muscle fatigue estimated muscle fatigue in 8 arm muscles. A self-selected pace (22.7 s), 12 s pace (Rule 8.04 from the MLB) and a 20 s rest (a pitch clock examined in the 2014 Arizona Fall League (AFL)) were examined. Significantly more muscle fatigue existed in both the AFL and Rule 8.04 conditions, when compared to the self-selected pace condition (5.01 ± 1.73%, 3.95 ± 1.20% and 3.70 ± 1.10% MVC force lost, respectively). Elevated levels of muscle fatigue are predicted in the flexor–pronator mass, which is responsible for providing elbow stability. Reduced effectiveness of the flexor–pronator mass may reduce the active contributions to joint rotational stiffness, increasing strain on the ulnar collateral ligament (UCL) and possibly increasing injury risk.     

人文体育观的建构：体育学的人文性和科学性 ——与布特博士的讨论提纲

认为体育学作为试图以理性把握人类体育整体的学科,因其目的和对象的非实体性,它应是一门人文教育理论学科,这是体育学存在价值和现代意义之所在.提出,体育学应在实践唯物论的人文主义基础上建树一种对人的终极价值关怀的人文体育观,由此出发通过反思、追问、评价现实体育提出的基本问题,建构它的理论体系.并讨论了体育学的科学性以及它与人文性有机结合问题,指出作为人文学科的体育学,其研究和学习本身就是检验道德和锻炼、发展人性的过程.     

Effects of rest interval during high-repetition resistance training on strength,aerobic fitness,and repeated-sprint ability

Abstract

The effect of altering the rest period on adaptations to high-repetition resistance training is not well known. Eighteen active females were matched according to leg strength and repeated-sprint ability and randomly allocated to one of two groups. One group performed resistance training with 20-s rest intervals between sets, while the other group employed 80-s rest intervals between sets. Both groups performed the same total training volume and load. Each group trained 3 days a week for 5 weeks [15- to 20-repetition maximum (RM), 2 – 5 sets]. Repeated-sprint ability (5×6-s maximal cycle sprints), 3-RM leg press strength, and anthropometry were determined before and after each training programme. There was a greater improvement in repeated-sprint ability after training with 20-s rest intervals (12.5%) than after training with 80-s rest intervals (5.4%) (P = 0.030). In contrast, there were greater improvements in strength after training with 80-s rest intervals (45.9%) than after training with 20-s rest intervals (19.6%) (P = 0.010). There were no changes in anthropometry for either group following training. These results suggest that when training volume and load are matched, despite a smaller increase in strength, 5 weeks of training with short rest periods results in greater improvements in repeated-sprint ability than the same training with long rest periods.     

“三从一大”训练原则在竞技体育不同项群训练中应用的理论与实践探究

阐述了"三从一大"从20世纪60年代初提出至今的40年中,其科学内涵从"训练方针"、"训练思想"到"训练原则"不断演变历程;演绎出各项目在运动训练实践过程中,曾经产生几大误区;结合不同项群的制胜规律与运动训练实践分别探析了各项群"从严"、"从难"、"从实战"和"大运动量"训练的科学内涵要点.