Multi-optimisation of the screw kick in rugby by using a genetic algorithm

This paper describes the use of Pareto-optimal solutions for the screw kick in rugby. We attempted to optimise the initial conditions for a screw kick. The optimisation was carried out using an elitist non-dominated sorting genetic algorithm. Distance achieved in flight is considered as an objective function, as well as the lateral deviation between the ball and the touchline, or the flight time. Six initial conditions were defined as control parameters: the magnitude of the velocity vector, the flight path angle, the azimuth angle, the spin rate, the pitch angle and the yaw angle. The results are summarised as follows: it is impossible for both objective functions to be satisfied simultaneously, although the greatest distance achieved in flight and the smallest value of the lateral deviation between the ball and the touchline, or the least flight time, is the ideal situation. This kind of conflicting solution is called a ‘Pareto-optimal solution’. The optimal kick in Pareto-optimal solutions made by the leg nearest the touchline produces a greater flight distance than the optimal kick in Pareto-optimal solutions made using the leg furthest from the touchline. The initial pitch angle, which is the angle between the longitudinal axis of the ball and the horizontal plane, should be comparable to or slightly greater than the initial flight path angle in order to satisfy the Pareto-optimal solutions.     

沈阳体育学院橄榄球运动员身体机能形态素质特征研究

采用实地观察法、指标测量法以及数理统计法对沈阳体育学院12名橄榄球运动员身体机能形态素质特征进行研究。结果表明:沈阳体育学院橄榄球运动员在身体形态上已经表现出专项特点,但是在心肺功能、反应速度以及相对力量等身体素质指标上和国内强队相比还有一定差距。因此,应加强沈阳体育学院橄榄球运动员力量、反应速度以及心肺功能的训练。     

浅析在中国开展英式橄榄球运动的可行性方法和途径

英式橄榄球运动作为一项深受世界各国人民喜爱的球类运动,于1990年传人中国大陆.但是十多年来,由于各种原因,致使英式橄榄球运动在中国大陆开展缓慢.为进一步推广英式橄榄球运动,让更多的人了解和参与这项运动,通过研究英式橄榄球的发展史和现阶段开展的情况,探索在中国大陆开展英式橄榄球运动的可行性方法和途径.     

Season-long increases in perceived muscle soreness in professional rugby league players: role of player position,match characteristics and playing surface

Rugby League (RL) is a high-impact collision sport characterised by repeated sprints and numerous high-speed impacts and consequently players often report immediate and prolonged muscle soreness in the days after a match. We examined muscle soreness after matches during a full season to understand the extent to which match characteristics influence soreness. Thirty-one elite Super League players provided daily measures of muscle soreness after each of the 26 competitive fixtures of the 2012 season. Playing position, phase of the season, playing surface and match characteristics were recorded from each match. Muscle soreness peaked at day 1 and was still apparent at day 4 post-game with no attenuation in the magnitude of muscle soreness over the course of the season. Neither playing position, phase of season or playing surface had any effects on the extent of muscle soreness. Playing time and total number of collisions were significantly correlated with higher ratings of muscle soreness, especially in the forwards. These data indicate the absence “contact adaptations” in elite rugby players with soreness present throughout the entire season. Strategies must now be implemented to deal with the physical and psychological consequences of prolonged feeling of pain.     

A Portrait of a Rugby Man with a ‘Broken Face’ Le Flambeau dans la nuit (Torch in the Night) (1927) by Henry Decoin

Although the historiography of the First World War has, on numerous occasions, examined deaths and injuries, and their causes and social impacts, only a small number of historians have studied the physical and mental consequences among athletes. While literature offers a way to portray a world that is devoid of substance, where characters are searching for escape, war writing raises the question of human beings' vulnerability. Based on the story of a rugby man with a ‘broken face', the article will consider how a former international rugby champion was unable to reintegrate back into himself into civilian life after losing his sight during the fighting. Henri Decoin was therefore an unusual witness to the First World War, who raised the existential issue faced by all ‘broken faces’, that is to say how to learn to live in society again with faces that bore the marks of war? With the literary character of ‘blind soldier’ deserving greater attention, that of the blind soldier-cum-sports champion has been given particular focus here, inasmuch as such a champion embodied a model of corporal excellence. Analysis of the novel Le Flambeau dans la nuit (Torch in the Night), published in 1927, explains how experience of life on the Western Front quite literally altered perceptions of the world for writers of the young generation. It is also observed how masculinity was called into question under the sign of disability, particularly within the rugby milieu. With few resources allowing reading of what the disfigured said about their mutilated bodies, beyond the information given by associations or in medical writings, this novel is indeed seen as a precious and useful source of information for historians.     

The effect of ball carrying method on sprint speed in rugby union football players

Different methods of ball carrying can be used when a player runs with the ball in rugby union. We examined how three methods of ball carrying influenced sprinting speed: using both hands, under the left arm and under the right arm. These methods were compared with running without the ball. Our aim was to determine which method of ball carrying optimizes sprinting speed. Altogether, 48 rugby union players (age 21±2 years, height 1.83±0.1?m, body mass 85.3±12?kg, body fat 14?±?5%; mean±s) were recruited. The players performed twelve 30-m sprints in total (each player performed three trials under each of three methods of carrying the ball and sprinting without the ball). The design of the study was a form of Latin rectangle, balanced across the trial order for each of the methods and for pairwise combinations of the methods in blocks of four per trial. Each sprint consisted of a 10-m rolling start, followed by a 20-m timed section using electronic timing gates. Compared with sprinting 20?m without the ball (2.58±0.16?s), using both hands (2.62±0.16?s) led to a significantly slower time (P?<0.05). Sprinting 20?m with the ball under the left arm (2.61±0.15?s) or under the right arm (2.60± 0.17?s) was significantly quicker than when using ‘both hands’ (P?<0.05), and both these methods were significantly slower than when running without the ball (P?<0.05). Accordingly, running with the ball in both hands led to the greatest decrement in sprinting performance, although carrying the ball under one arm also reduced the players' sprinting ability. Our results indicate that to gain a speed advantage players should carry the ball under one arm.     

Influence of training and match intensity on injuries in rugby league

The aim of this study was to examine the influence of perceived intensity, duration and load of matches and training on the incidence of injury in rugby league players. The incidence of injury was prospectively studied in 79 semi-professional rugby league players during the 2001 season. All injuries sustained during matches and training sessions were recorded. Training sessions were conducted from December to September, with matches played from February to September. The intensity of individual training sessions and matches was estimated using a modified rating of perceived exertion scale. Training load was calculated by multiplying the training intensity by the duration of the training session. The match load was calculated by multiplying the match intensity by the time each player participated in the match. Training load increased from December (278.3 [95% confidence interval, CI 262.2 to 294.5] units) to February (385.5 [95% CI 362.4 to 408.5] units), followed by a decline until September (98.4 [95% CI 76.5 to 120.4] units). Match load increased from February (204.0 [95% CI 186.2 to 221.8] units) to September (356.8 [95% CI 302.5 to 411.1] units). More training injuries were sustained in the first half of the season (first vs second: 69.2% vs 30.8%, P?<0.001), whereas match injuries occurred more frequently in the latter stages of the season (53.6% vs 46.4%, P?<0.001). A significant relationship (P?<0.05) was observed between changes in training injury incidence and changes in training intensity (r?=?0.83), training duration (r?=?0.79) and training load (r?=?0.86). In addition, changes in the incidence of match injuries were significantly correlated (P?<0.05) with changes in match intensity (r?=?0.74), match duration (r?=?0.86) and match load (r?=?0.86). These findings suggest that as the intensity, duration and load of rugby league training sessions and matches is increased, the incidence of injury is also increased.     

An objective method for depicting team performance in elite professional rugby union

Abstract

Using a two-study approach, we examined a methodology for objectively depicting team performance and form in a professional rugby union side. Study 1 developed standardized indicators to examine a team's performance in a single match relative to their previous matches over a domestic season via a performance report and form chart. This resulted in standardized performance indicators that provided instant and coherent feedback on the team's performance relative to previous standards. Study 2 then utilized this methodology to compare a match between two professional sides, played the following season, to assess the extent to which the performance by one team affected that of the other. Comparison of the two teams' performances, for the match they played against each other, identified a drop in relative performance (against previous standards) for both teams on the same performance indicators. This appeared to be due to the match being a close, hard-fought contest particularly in the tackle and around the gain-line. The findings of the two studies suggest an accurate and viable methodology for depicting team performance that is superior to the global measures previously adopted. Presenting teams' current standardized performances (i.e. form) on a single visual scale also has utility for coaches within an applied setting. Future research should further investigate the effect of one team's performance on another through both individual and team outcomes.     

Upper-body repeated-sprint training in hypoxia in international rugby union players

Abstract

This study investigated the effects of upper-body repeated-sprint training in hypoxia vs. in normoxia on world-level male rugby union players’ repeated-sprint ability (RSA) during an international competition period. Thirty-six players belonging to an international rugby union male national team performed over a 2-week period four sessions of double poling repeated-sprints (consisting of 3 × eight 10-s sprints with 20-s passive recovery) either in normobaric hypoxia (RSH, simulated altitude 3000 m, n?=?18) or in normoxia (RSN, 300 m; n?=?18). At pre- and post-training intervention, RSA was evaluated using a double-poling repeated-sprint test (6 × 10-s maximal sprint with 20-s passive recovery) performed in normoxia. Significant interaction effects (P?<?0.05) between condition and time were found for RSA-related parameters. Compared to Pre-, peak power significantly improved at post- in RSH (423?±?52 vs. 465?±?69 W, P?=?0.002, η²=0.12) but not in RSN (395?±?65 vs. 397?±?57 W). Averaged mean power was also significantly enhanced from pre- to post-intervention in RSH (351?±?41 vs. 388?±?53 W, P?<?0.001, η²=0.15), while it remained unchanged in RSN (327?±?49 vs. 327?±?43 W). No significant change in sprint decrement (P?=?0.151, η²?=?0.02) was observed in RSH (?17?±?2% vs. ?16?±?3%) nor RSN (?17?±?2% vs. ?18?±?4%). This study showed that only four upper-body RSH sessions were beneficial in enhancing repeated power production in international rugby union players. Although the improvement from RSA to game behaviour remains unclear, this finding appears of practical relevance since only a short preparation window is available prior to international games.     

普通高校开展英式橄榄球运动的探索研究

通过文献资料法和调查访问法,对华南农业大学开展将近20年的英式橄榄球运动给予总结,从教学研究、运动训练和学生社团3个方面介绍华南农业大学开展英式橄榄球运动的现状,并提出在普通高校开展英式橄榄球运动的结论和建议。