Effect of the starting and turning performances on the subsequent swimming parameters of elite swimmers

In the present research, we examined the effect of the starting and turning performances on the subsequent swimming parameters by (1) comparing the starting and turning velocities with the swimming parameters on the emersion and mid-pool segments and (2) by relating the individual behaviour of swimmers during the start and turns with subsequent behaviour on each swimming lap. One hundred and twelve 100 m performances on the FINA 2013 World Swimming Championships were analysed by an image-processing system (InThePool 2.0®). At the point of the start emersion, the swimming parameters of the 100-m elite swimmers were substantially greater than the mid-pool parameters, except on the breaststroke races. On the other hand, no diminution in the swimming parameters was observed between the turn emersion and the mid-pool swimming, except on the butterfly and backstroke male races. Changes on the surface swimming kinematics were not generally related to the starting or turning parameters, although male swimmers who develop faster starts seem to achieve faster velocities at emersion. Race analysts should be aware of a transfer of momentum when swimmers emerge from underwater with implications on the subsequent swimming kinematics, especially for male swimmers who employ underwater undulatory techniques.     

山东省优秀女子竞走运动员专项技术动作分析

本研究选取6名现役的优秀竞走运动员,采用二维摄像并使用APAS动作解析软件和Dartdfish软件对录像进行解析,发现杨、王和李的步频较慢,建议在训练时多进行提高步幅的练习;曹、董、刘、李的速度损失率过大,尤其是董最大,可能是由于在支撑腿在蹬离地面时的用力方式不对或者动作结构错误造成的。建议在日常训练的过程中加强运动员的支撑腿在蹬离地面时用力方式和动作结构的练习;董、杨、李头顶起伏过大,建议在训练中注意控制头顶起伏。     

Total kinetic energy production of body segments is different between racing and training paces in elite Olympic rowers

Total kinetic energy (TKE) was calculated for 28 Canadian national team Olympic rowers during training on water, comparing low-stroke rates (18–22 stroke/min) and high-stroke rates (32–40 stroke/min), using video analysis. Stroke duration was normalized to 100%, beginning and ending at the “catches”, with the drive phase occurring first and recovery second. Two discrete points were identified during the stroke, both occurring when the fingers had the same horizontal position as the ankles (i.e. mid-drive and mid-recovery). The ratios of recovery-to-drive TKE at these points for the entire body at low and high-stroke rates were 0.36 ± 0.34 and 1.26 ± 0.54 respectively. Significant differences were found for the lower leg, upper arm and forearm segments, and within the female groups. Low-stroke rate is a typical training pace and high-stroke rate is analogous to a race pace. This study demonstrates that TKE production during recovery in a race was not replicated during training. While training at low-stroke rates is vital for technique refinement, this study stresses the importance of training appropriately for the energy expenditure during high-stroke rate recovery. This is commonly overlooked by coaches and athletes.     

Competitive balance trends in elite table tennis: the Olympic Games and World Championships 1988-2016

ABSTRACT

Competitive balance is important because it enhances outcome uncertainty and therefore it promotes spectator interest, and encourages government investment in a sport. This article analyses the distribution of gold medals, medals, medal points and top eight points amongst nations in table tennis from 1988 to 2016 at the Olympic Games and the World Championships respectively. A normalised version of the Herfindahl-Hirschman Index and a coefficient of variation are calculated for each nation’s share of these performance indicators. The key findings are that China dominates both events, with successful female players being more dominant than their male counterparts. The competitive balance for gold medals has declined, whilst there is a trend towards improved competitive balance for top eight points for women, suggesting that more teams are featuring in the top eight (but not necessarily the top three) placings. This research has implications for the development of table tennis competitions. Compared to other racket sports, the issue of competitive imbalance in table tennis is particularly thorny, which threatens the long-term development of this sport. Accordingly, some measures are recommended for the International Olympic Committee and the International Table Tennis Federation to propel a more balanced development of international table tennis.     

Pacing profiles and pack running at the IAAF World Half Marathon Championships

The aim of this study was to describe the pacing profiles and packing behaviour of athletes competing in the IAAF World Half Marathon Championships. Finishing and split times were collated for 491 men and 347 women across six championships. The mean speeds for each intermediate 5 km and end 1.1 km segments were calculated, and athletes grouped according to finishing time. The best men and women largely maintained their split speeds between 5 km and 15 km, whereas slower athletes had decreased speeds from 5 km onwards. Athletes were also classified by the type of packing behaviour in which they engaged. Those who ran in packs throughout the race had smaller decreases in pace than those who did not, or who managed to do so only to 5 km. While some athletes’ reduced speeds from 15 to 20 km might have been caused by fatigue, it was also possibly a tactic to aid a fast finish that was particularly beneficial to medallists. Those athletes who ran with the same competitors throughout sped up most during the finish. Athletes are advised to identify rivals likely to have similar abilities and ambitions and run with them as part of their pre-race strategy.     

中外优秀男子400 m栏选手栏间技术的比较

通过大量的资料和文献查阅,概述了男子400 m栏栏间跑技术的分类及技术要点。以国内外部分优秀男子400 m栏运动员为例,从栏间跑技术节奏、栏间跑速度及栏间变化跑等3个方面对国内外优秀选手栏间跑技术做了系统的比较分析,了解国内选手在栏间跑技术方面与国外选手的差距,提出了改善国内选手栏间跑技术的建议,为今后栏间技术训练制定更科学、合理的计划提出参考,以帮助国内选手优化栏间跑技术。     

A biomechanical comparison of initial sprint acceleration performance and technique in an elite athlete with cerebral palsy and able-bodied sprinters

Abstract

Cerebral palsy is known to generally limit range of motion and force producing capability during movement. It also limits sprint performance, but the exact mechanisms underpinning this are not well known. One elite male T36 multiple-Paralympic sprint medallist (T36) and 16 well-trained able-bodied (AB) sprinters each performed 5–6 maximal sprints from starting blocks. Whole-body kinematics (250 Hz) in the block phase and first two steps, and synchronised external forces (1,000 Hz) in the first stance phase after block exit were combined to quantify lower limb joint kinetics. Sprint performance (normalised average horizontal external power in the first stance after block exit) was lower in T36 compared to AB. T36 had lower extensor range of motion and peak extensor angular velocity at all lower limb joints in the first stance after block exit. Positive work produced at the knee and hip joints in the first stance was lower in T36 than AB, and the ratio of positive:negative ankle work produced was lower in T36 than AB. These novel results directly demonstrate the manner in which cerebral palsy limits performance in a competition-specific sprint acceleration movement, thereby improving understanding of the factors that may limit performance in elite sprinters with cerebral palsy.     

Relative age effect and performance in the U16, U18 and U20 European Basketball Championships

This study sought to determine the association of relative age and performance of young elite basketball players. The distribution of the birth dates, heights, positions, classification and performance of the male and female participants (n = 2395) of the U16, U18 and U20 European Basketball Championships were analysed. We found an over-representation of players born during the initial months of the year in all groups, with the relative age effect being more evident in players of the U16 and U18 groups, than of the U20 teams, particularly in male squads. Nevertheless, in the U20 championships, those teams that had the oldest players performed the best. In all championships, the oldest participants played more minutes. In addition, relatively older male players scored better in total points and in performance index rating when results were normalised to played time. This effect was not found for female players. Regarding playing position, different distributions of birth dates were observed due to each position’s physical requirements. Thus, basketball coaches and managers should keep these results in mind when they select players because if not, they might subject players who are born towards the end of the year to a negative selection bias.     

因子分析在学生十项全能成绩分析中的应用

应用SPSS统计软件，对常德师院体育教育专业122名男生十项全能成绩进行了因子分析。用主成分法提取4个公因子，第1公因子支配100m、400m、1500m和110m栏，反映了速度和耐力；第2公因子支配铅球、铁饼和标枪，反映了上肢爆发力；第3公因子支配跳远和跳高。反映了下肢弹跳力；第4公因子支配撑杆跳高，反映了综合素质；根据学生的因子得分可将学生分为速度耐力型、上肢力量型、下肢力量型和综合素质型4类。     

Effects of strength training on physical fitness and sport-specific performance in recreational,sub-elite,and elite rowers: A systematic review with meta-analysis

ABSTRACT

The purpose of this systematic review with meta-analysis was to examine the effects of strength training (ST) on selected components of physical fitness (e.g., lower/upper limb maximal strength, muscular endurance, jump performance, cardiorespiratory endurance) and sport-specific performance in rowers. Only studies with an active control group were included if they examined the effects of ST on at least one proxy of physical fitness and/or sport-specific performance in rowers. Weighted and averaged standardized mean differences (SMD) were calculated using random-effects models. Subgroup analyses were computed to identify effects of ST type or expertise level on sport-specific performance. Our analyses revealed significant small effects of ST on lower limb maximal strength (SMD = 0.42, p = 0.05) and on sport-specific performance (SMD = 0.32, p = 0.05). Non-significant effects were found for upper limb maximal strength, upper/lower limb muscular endurance, jump performance, and cardiorespiratory endurance. Subgroup analyses for ST type and expertise level showed non-significant differences between the respective subgroups of rowers (p ≥ 0.32). Our systematic review with meta-analysis indicated that ST is an effective means for improving lower limb maximal strength and sport-specific performance in rowers. However, ST-induced effects are neither modulated by ST type nor rowers’ expertise level.     

第48 届世乒赛马琳技术统计分析

对马琳在第48届世乒赛进入男单前8名后三场比赛的发球抢攻段、接发球抢攻段和相持段技战术特点进行统计分析，通过定量研究，找出了其在技术、战术上存在的优势和不足，为未来训练提供科学依据，并为进一步提高我国传统直拍快攻打法的技战术水平提出了一些建议，以供乒乓同仁参考。     

Analysis of the distances covered and technical actions performed by professional tennis players during official matches

The purpose of this study was to analyse the physical and technical performances of professional tennis players during official matches. The trajectories of eight players were obtained during matches, using an automatic tracking method. The distances covered and technical performances were analysed for the first and second sets. The athletes covered (mean ± standard deviation) a total of 1702.4 ± 448.2 m in the first set, 1457.6 ± 678.1 m in the second set and 3160.0 ± 880.1 in the entire match. No differences were found between the sets for the physical variables (lateral and forward displacements, distance covered per rally, per game and per set, and the percentage of time spent in each range of velocity). However, the distances covered by the athletes during the rallies in which they were serving (median = 5.2; interquartile range (IQR) = 6.7 m) were statistically smaller than when they were returning (median = 6.2; IQR = 7.7 m). Forehand ground stroke proficiency decreased from the first (mean ± standard deviation: 75.2 ± 4.11%) to the second set (mean ± standard deviation = 65.5 ± 14.3%). In conclusion, tennis players did not present reduced physical performance from the first to the second set.     

全国跆拳道锦标赛系列赛男子58公斤级击头技术运用分析

目的 分析优秀运动员在比赛中腿法击头技术,为分析当前击头技术动作规律现状、科学优化训练下肢击头技术动作,缩短与对手的差距给予重要启示.方法 录像观察法、数理统计法.结果 1)横踢、下劈踢、侧踢击头技术在进攻、迎击、反击三种常用战术中占据主导位置.2)进攻战术中横踢的使用率得分率最高,但成功率下劈踢技术最高.3)迎击战术...     

Network analysis of kick-in possession chains in elite Australian football

ABSTRACT

The study aim was to investigate ball movement patterns using network analysis techniques, to compare between successful and unsuccessful outcomes and teams in the Australian Football League (AFL). This analysis focused on possession chains starting from a kick-in (n = 1,720), drawn from all games played in the 2015 AFL Premiership season (18 teams, 206 games). Player interactions were quantified using four network metrics: cluster coefficient, degree centrality, network density, and entropy. Three-way ANOVA with Tukey post hoc and ω² effect sizes were calculated to assess whether differences existed between kick-in outcomes, ladder brackets, and match outcomes for each network metric. No significant differences were observed between ladder brackets or match outcomes for any network metric. More successful kick-in chains were characterised by lower density (ω² = 0.26, large effect; F(9, 1678) = 66.6, p < 0.00) and higher entropy (ω² = 0.17, large effect; F(9, 1678) = 39.6, p < 0.00). This suggests that chains resulting in successful kick-in outcomes exhibited lower interconnectedness, with a high number of players involved, and lower predictability in ball movement patterns. These findings have practical value for coaches and performance analysts and support further applications of network analysis in Australian football.     

对中外优秀十项全能运动员比赛成绩的灰色协调分析

男子十项全能是一项复杂的综合性竞技项目，也是一个典型的灰色系统。运用GM（1，N）动态协调模型对国内外全能选手在总成绩不断提高的各个阶段中各因素间相互联系，相互影响的辩证发展关系进行多方位、多层次的分析，揭示了身体素质中速度与力量这对主要矛盾因素的互相促进和制约是十项全能水平不断提高与发展的关键，同时也揭示了速度与力量的发展失衡是我国男子十项全能选手成绩徘徊不前的主要原因。     

第11届世界女子垒球锦标赛四强实力分析

以参加2006年8月27日~9月5日在北京举行的第11届世界女子垒球锦标赛前4名队伍为研究对象,对其在本次比赛中的各项技、战术指标进行统计分析。研究认为,在强强对阵中,美国队有着超强的进攻能力和有效的防守能力,总体实力处在“超级霸主”地位,日本与澳大利亚队进攻实力相当,防守水平日本队强于澳大利亚队,中国队的进攻和防守实力明显比前3名队伍逊色;中国队投手的总体实力不比前3名队伍逊色,但缺少明星投手。     

Kinematic comparison of the seoi-nage judo technique between elite and college athletes

This study sought to identify biomechanical factors that determine fast and skilful execution of the seoi-nage (shoulder throw) technique by comparing kinematics between elite and college judo athletes. Three-dimensional motion data were captured using a VICON-MX system with 18 cameras operating at 250 Hz as three male elite and seven male college judo athletes performed seoi-nage. No significant difference was found in motion phase time of the turning phase between the two groups, indicating that motion phase time is not necessarily a factor contributing quickness in seoi-nage. The maximum relative velocity of the whole body centre of mass along the anterior–posterior direction was significantly greater in the elite athletes (2.74 ± 0.33 m/s) than in the college athletes (1.62 ± 0.47 m/s) during the turning phase (p = 0.023). The overall angular velocity of the body part lines, particularly the arm line, tended to be greater in the elite athletes (p = 0.068). The results imply that the velocity of the thrower relative to the opponent in the forward drive and turning motion reflects high skill seoi-nage. Coaches should recognise the relative forward velocity as a factor that may contribute to a successful seoi-nage when teaching the judo throw technique.     

九运会场地自行车女子500 m计时赛出发动作的运动生物力学分析

自行车计时赛项目的出发动作是影响成绩的关键环节.采用运动生物力学研究方法,对参加九运会500m计时赛的15名运动员的出发动作及途中速度进行了研究.     

我国优秀女排队员移动拦网技术动作解析

1前言近年来世界排球大赛的实践表明，拦网已从单一的防守技术转变为攻防兼备的制胜技术之一。拦网水平的高低不仅直接影响比赛的胜负，而且也是衡量一支球队技战术水平的重要标志之一，因此，备受国内外教练员和科研工作者的关注。长期以来，有关拦网技术的研究，仅限于现场统     

Modelling relationships between match events and match outcome in elite football

Identifying match events that are related to match outcome is an important task in football match analysis. Here we have used generalised mixed linear modelling to determine relationships of 16 football match events and 1 contextual variable (game location: home/away) with the match outcome. Statistics of 320 close matches (goal difference ≤ 2) of season 2012–2013 in the Spanish First Division Professional Football League were analysed. Relationships were evaluated with magnitude-based inferences and were expressed as extra matches won or lost per 10 close matches for an increase of two within-team or between-team standard deviations (SD) of the match event (representing effects of changes in team values from match to match and of differences between average team values, respectively). There was a moderate positive within-team effect from shots on target (3.4 extra wins per 10 matches; 99% confidence limits ±1.0), and a small positive within-team effect from total shots (1.7 extra wins; ±1.0). Effects of most other match events were related to ball possession, which had a small negative within-team effect (1.2 extra losses; ±1.0) but a small positive between-team effect (1.7 extra wins; ±1.4). Game location showed a small positive within-team effect (1.9 extra wins; ±0.9). In analyses of nine combinations of team and opposition end-of-season rank (classified as high, medium, low), almost all between-team effects were unclear, while within-team effects varied depending on the strength of team and opposition. Some of these findings will be useful to coaches and performance analysts when planning training sessions and match tactics.