Dynamics of visual feedback in a laboratory simulation of a penalty kick

Sport scientists have devoted relatively little attention to soccer penalty kicks, despite their decisive role in important competitions such as the World Cup. Two possible kicker strategies have been described: ignoring the goalkeeper action (open loop) or trying to react to the goalkeeper action (closed loop). We used a paradigm simulating a penalty kick in the laboratory to investigate the dynamics of the closed-loop strategy in these controlled conditions. The probability of correctly responding to the simulated goalkeeper motion as a function of time available followed a logistic curve. Kickers on average reached perfect performance only if the goalkeeper committed him or herself to one side about 400 ms before ball contact and showed chance performance if the goalkeeper motion occurred less than 150 ms before ball contact. Interestingly, coincidence judgement?-?another aspect of the laboratory responses?-?appeared to be affected for a much longer time (>500 ms) than was needed to correctly determine laterality. The present study is meant as groundwork for experiments in more ecological conditions applicable to kickers and goalkeepers.     

Dynamics of visual feedback in a laboratory simulation of a penalty kick

Sport scientists have devoted relatively little attention to soccer penalty kicks, despite their decisive role in important competitions such as the World Cup. Two possible kicker strategies have been described: ignoring the goalkeeper action (open loop) or trying to react to the goalkeeper action (closed loop). We used a paradigm simulating a penalty kick in the laboratory to investigate the dynamics of the closed-loop strategy in these controlled conditions. The probability of correctly responding to the simulated goalkeeper motion as a function of time available followed a logistic curve. Kickers on average reached perfect performance only if the goalkeeper committed him or herself to one side about 400 ms before ball contact and showed chance performance if the goalkeeper motion occurred less than 150 ms before ball contact. Interestingly, coincidence judgement--another aspect of the laboratory responses--appeared to be affected for a much longer time (> 500 ms) than was needed to correctly determine laterality. The present study is meant as groundwork for experiments in more ecological conditions applicable to kickers and goalkeepers.     

足球守门员在防守点球运动情境中眼动特征的研究

采用美国应用科学实验室(ASL)生产的504型眼动仪,以10名专业足球守门员和10名大学生足球守门员为被试,以防守点球为运动情境片段,对专业守门员的眼动特征进行实验性研究,比较两组守门员的眼动实验结果,探讨守门员在防守点球时眼动特征对决策准确性的影响.实验结果表明:1)在防守点球情境中,专业守门员与大学生守门员的眼动特征存在明显差异;2)专业守门员采用了相对合理的视觉搜索策略,注视点集中,注视分配主次明显,注视轨迹简单、实用,信息实效性更强;3)罚球运动员的支撑脚、摆动腿、脚触球是决定射门方向的主要观察点.在防守时,重点注视这三个区域,结合临场经验做出分析判断,可有效提高防守点球成功率;4)运动水平和临场经验对准确做出防守决策至关重要,运动水平越高,临场经验越丰富,防守决策准确率越高.     

Goalkeeping in the soccer penalty kick

The goalkeeper’s difficulty in the soccer penalty kick originates from the extreme spatiotemporal constraints of the situation. The present review claims that the current understanding is biased toward attributing a goalkeeper’s success in saving a penalty kick to perceptual–cognitive skill. To investigate the goalkeeper’s skill, researchers have often adopted video tasks. In doing so, they studied perceptual skill in isolation from action. We use affordance-based control theory to propose an alternative understanding and research methodology. We argue that goalkeepers in the penalty kick situation should regulate their actions in ways that sustain the perception of stoppability. To capture this, we outline the building blocks for a required lateral velocity model, in which the goalkeepers’ required actions are scaled to their maximum capabilities. In doing so, we provide new directions for research.     

Analysis of direct free kicks in the women's football World Cup 2007

Abstract

The location and outcome of all free kicks taken directly at goal in the 2007 women's football World Cup were assessed to identify areas with the most goal-scoring potential and assist with tactical decisions and training design. Video of all free kicks taken directly at goal in the 32 games was captured and the location of the ball on the pitch was calculated from pitch markings and image pixel coordinates using a customized curve-fitting method. The outcome of each free kick was determined and for those that resulted in a goal or were saved, information on ball flight time and the placement of the ball relative to the goal was reported. All seven free kicks that resulted in a goal were taken from a central area within 7 m of the penalty circle, placed at the edge of the goal within approximately 1 m of the goalpost, and had an average flight time of 1.09 s, which was significantly faster than for those that were saved. All free kicks directed towards the bottom and centre of the goal resulted in straightforward saves for the goalkeeper. It is recommended that teams should consider a direct shot from free kicks awarded within 7 m of the penalty circle. For free kicks from wide areas and areas further from the goal, players should be aware of their individual ability and only take a shot when they perceive the probability of scoring a goal to be high. Otherwise, alternative attacking strategies should be considered to avoid an easy turnover of possession.     

国外足球点球心理研究进展

点球是现代足球竞赛中的重要技术,对比赛结果具有显著的影响。点球心理研究是足球心理研究中的热点议题。该文从队服颜色效应、罚球员与守门员的非言语行为、罚球员射门策略以及预测罚球员射门区域的先行线索等四个方面对国外足球点球心理研究现状进行了系统回顾与总结,认为每个影响守门员或罚球员的因素均可应用于守门员或罚球员的指导与训练。在对国外研究现状分析的基础上提出了未来的研究方向提高研究的生态学效度与加强质性研究,重视心理干预研究以提升球员的抗压能力。     

Attention towards the goalkeeper and distraction during penalty shootouts in association football: a retrospective analysis of penalty shootouts from 1984 to 2012

In the present study, we tested the consequences of attention towards goalkeepers in association football penalty shootouts that have exclusively been derived from laboratory experiments. We conducted a retrospective analysis of all penalty shootouts during FIFA World Cups (1986–2010) and UEFA European Football Championships (1984–2012). We linked key variables of previous laboratory research to observable behaviour in the field that was coded by two independent coders. The following hypotheses were tested: first, attention towards goalkeepers results in more saves/better goalkeeper performance; second, goalkeepers can deliberately distract penalty takers by drawing attention towards themselves which results in less accurate penalty kicks/better goalkeeper performance. Results were in line with previous laboratory analyses as they showed that attention towards goalkeepers resulted in more saves/better goalkeeping performance. Further, if goalkeepers distracted penalty takers this also resulted in better goalkeeping performance. The applied implications of these findings are discussed for both goalkeepers and penalty takers in association football.     

浅谈“香蕉球”的力学原理

你经常观看足球比赛的话，可以看到球绕过了“人墙”，眼看要偏离球门飞出，却又沿弧线拐过弯来直入球门，让守门员措手不及，眼睁睁地看着球进了大门。这就是颇为神奇的“香蕉球”。那么“香蕉球”是怎样踢出来的呢？本论文将对此进行研究。目的：怎样才能踢出“香蕉球”和“香蕉球”是如何形成的。分析方法：运用基础的物理知识——流体力学和动力学对球的运动和受力进行分析。结论：当人给球力的有个角度（0〈α〈90），就可以让球发生旋转，经过一定的位移后在风力的作用下球会呈弧线运动，而产生了“香蕉球”。在足球运动中，通过这样的球能让守门员防不胜防，达到进球的目的。     

How does the modern football goalkeeper train? – An exploration of expert goalkeeper coaches’ skill training approaches

ABSTRACT

The football goalkeeper position arguably represents a unique role within the team sport. Despite its highly complex skill demands, research on football goalkeeping has only sporadically examined the position within isolated and limited parameters. In particular, there is limited literature on “modern” skill acquisition training methods and approaches within the field of goalkeeper training. In a cross-cultural study with fifteen expert goalkeeper coaches, researchers here examined the overarching research question of “how does the modern football goalkeeper train?”. Semi-structured interviews explored expert coaches’ views on critical skills for performance in goalkeeping and the training approaches used to develop these critical skills. Results indicate that four skill sets are considered essential by goalkeeper coaches, these are: decision-making skills, athleticism, mentality, and technical skills. In terms of developing these skills in goalkeeper-specific training, the majority of expert coaches apply a similar microstructure to training sessions. This structure involves a steady progression from simple to complex training tasks, where for large parts, isolated technical training appears to be prioritised over a holistic training approach that integrates technical skills and perceptual-cognitive components (e.g., decision making). Scientific and practical recommendations for researchers and practitioners in the field of football goalkeeper coaching are provided.     

Aerodynamic effects on the accuracy of an end-over-end kick of an American football

The effects of initial conditions on the flight of an American football kicked in an end-over-end manner were investigated using a dynamic simulation employing the quaternion method. The effects of initial tilt and spin about the longitudinal axis of the ball were considered. For the most accurate kick, our simulations show that the ball should be vertical leaving the kicker’s foot, and have no angular velocity about the longitudinal axis of the ball. A case study was performed for which experimental data were available, showing the trends of the flight of the ball captured in our simulations in actual game situations.     

The development of a method for identifying penalty kick strategies in association football

Penalty takers in association football adopt either a keeper-independent or a keeper-dependent strategy, with the benefits of the keeper-independent strategy presumed to be greater. Yet, despite its relevance for research and practitioners, thus far no method for identifying penalty kick strategies has been available. To develop a validated and reliable method, Experiment 1 assessed characteristics that observers should use to distinguish the two strategies. We asked participants to rate 12 characteristics of pre-recorded clips of kicks of penalty takers that used either a keeper-independent or keeper-dependent strategy. A logistic regression model identified three variables (attention to the goalkeeper, run-up fluency and kicking technique) that in combination predicted kick strategy in 92% of the penalties. We used the model in Experiment 2 to analyse prevalence and efficacy of both the strategies for penalty kicks in penalty shoot-outs during FIFA World Cups (1986–2010) and UEFA Football Championships (1984–2012). The keeper-independent strategy was used much more frequently (i.e., 78–86%) than the keeper-dependent strategy, but successes did not differ. Penalty takers should use both the strategies to be less predictable. Goalkeepers can use the developed model to improve their chances to succeed by adjusting their behaviour to penalty takers’ preferred penalty kick strategy.     

Spatial-temporal constraints on decision-making during shooting performance in the team sport of futsal

Abstract

In this paper we examined the influence of opposing players constraining the decision-making of an attacker during shooting performance in futsal. Performance during 10 competitive matches was recorded and examined from the moment a shot was taken until the ball was intercepted or entered the goal in sequences of play: ending in a goal, a goalkeeper's save, or an interception by the nearest defender. The variables under scrutiny in this study were (i) the distance of each player to the ball's trajectory, (ii) the time for the ball to arrive at that same point (i.e. the interception point), and (iii), the required movement velocity of the nearest defender and the goalkeeper to intercept the ball. Results showed that values of distance from a defender and goalkeeper to the interception points were significantly lower when they intercepted the ball. The time of ball arrival at the interception point of the defender was also lower when the ball was intercepted. The required velocities of the nearest outfield defender and the goalkeeper to intercept the ball were significantly lower during plays in which they intercepted the ball, than in plays in which the ball was not intercepted. Our results suggest that researchers and practitioners should consider simultaneously both space and time in analysis of interceptive actions in team sports. The required movement velocities of the opponents to intercept the ball are reliable spatial-temporal variables constraining decision-making during shooting performance in team sports like futsal.     

A field simulation study of the effectiveness of penalty kick strategies in soccer: Late alterations of kick direction increase errors and reduce accuracy

Abstract

This field experiment investigated the relative merits of approaching the penalty kick with either a keeper-independent or keeper-dependent strategy. In the keeper-independent strategy, the shooter selects a target location in advance and disregards the goalkeeper's actions during the run-up. In the keeper-dependent strategy, the shooter makes a decision resting on the anticipation of the goalkeeper's movements during the run-up. Ten intermediate-level soccer players shot at one of two visually specified targets to the right and left side of the goal. In the keeper-independent strategy condition, participants were told that the visually specified target would not change. In the keeper-dependent strategy condition, participants were told that in half of the trials the visually specified target would change side at different times before ball contact, indicating that the direction of the kick needed to be altered. The results showed that penalty-taking performance was apt to be less than perfect in the keeper-dependent strategy condition. A decrease in the time available to alter kick direction resulted in a higher risk of not only an incorrect but also inaccurate shot placement. It is concluded that anticipating the goalkeeper's movements may degrade penalty kick performance, mainly due to insufficient time to modify the kicking action.     

Investigation of toppling ball flight in American football with a mechanical field-goal kicker

A mechanical field-goal kicking machine was used to investigate toppling ball flight in American football place-kicking, eliminating a number of uncontrollable impact variables present with a human kicker. Ball flight trajectories were recorded using a triangulation-based projectile tracking system to account for the football’s 3-dimensional position during flight as well as initial launch conditions. The football flights were described using kinematic equations relating to projectile motion including stagnant air drag and were compared to measured trajectories as well as projectile motion equations that exclude stagnant air drag. Measured football flight range deviations from the non-drag equations of projectile motion corresponded to deficits between 9 and 31%, which is described by a football toppling compound drag coefficient of 0.007 ± 0.003 kg/m. Independent variables including impact location and impact angle orientation resulted in 15 impact conditions. We found that an impact location of 5.5 cm from the bottom of the ball maximized trajectory height and distance. At the 5.5-cm impact location, alterations in impact angle produced minimal change in football trajectory, including launch angle (range = 1.96 deg), launch speed (range = 1.06 m/s), and range (range = 0.94 m).     

足球赛场引入底线裁判的理性思考

近年来,足球赛场引入高科技判罚的呼声日益高涨.网球可以挑战鹰眼,而足球争议判罚往往出现在非死球状态下,此时起用录像判罚太不切实际,但规则中底线裁判出现,不仅能降低罚球区误判率,且仍是靠人力而非科技判罚,在国际足联不愿引入"门线技术"的背景下,实在没有将其拒之门外的理由.足球赛场增设底线裁判在足球规则变革中具有重要意义.     

Informational constraints on interceptive actions of elite football goalkeepers in 1v1 dyads during competitive performance

The aim of this study was to examine whether perceptual variables can provide informational constraints for the goalkeepers to intercept the ball successfully in 1v1 dyads. Video images of 42 actions (1v1 in direct shots) were selected randomly from different matches and divided into conceded goals (n = 20) and saved actions (n = 22) to investigate interceptive actions of 20 goalkeepers in the English Premier League in season 2013–2014. Time to Contact (TTC) of the closing distance gap between shooter and goalkeeper was obtained by digitising actions in the 18-yard penalty box. Statistical analyses revealed that, in sequences of play resulting in an intercepted shot at goal, goalkeepers closed down outfield players in the X axis, whereas when a goal was conceded, there was a significantly delayed movement by goalkeepers toward the shooters in this plane. The results of canonical correlations showed that a decreasing distance between a shooter and goalkeeper, and accompanied reduction in relative interpersonal velocity followed a temporal pattern. Findings of this study showed how perception of key informational constraints on dyadic system relations, such as TTC, interpersonal distance and relative velocity, constrain elite goalkeepers’ interceptive actions, playing an important role in successful performance.     

对足球守门员扑救球点球时机的研究

点球攻守是当今足球比赛中决定胜负的重要因素之一。本文通过大量数据分析推导得出,守门员在防守点球时的最佳扑救(反应)时机,应该选择在看到主罚队员最后一步助跑支撑脚上步离开地面的一瞬间,这样可以获得最佳的提前量。     

足球比赛中罚球点球决胜负策略与分析

研究目的:分析足球比赛中罚球点球中有关影响环节,为教练员、球员在罚球点球过程中提供策略依据的目的。研究方法:采用文献资料法、逻辑分析法、录像分析法。研究结果:在足球比赛中罚球点球技术动作环节、策略选择、顺序排列、影响因素等合理的应用会大大提高足球比赛中罚球点球中取胜的机率。研究结论:教练员在平时训练中要加强队员心理素质的培养、实施对队员抗干扰意志力的培养、训练队员快速形成一套自己的罚球点球程序、运用意象法训练队员克服比赛中的各种压力等。     

中小学武术教育研究之述评

文章研究了新中国建立以来武术教育的历史发展,对我国武术教育现状和发展两方面进行了总结分析,得出结论：师生的武术活动是改变当下武术教育尴尬境地、推进武术教育发展、传播民族文化、弘扬民族精神使命的需要。文章为武术教育的进一步研究奠定了基础,也为武术教育的进一步发展指明了新的研究方向。     

基于先验信息条件下足球守门员的知觉预测研究

目的：研究守门员基于先验信息下的知觉预测能力,探索当守门员处于射门方向（实际方向）与对手点球偏好（概率方向）一致或不一致的情境下,对表现有效性和加工效率的影响。方法：通过网络平台招募专业足球守门员（专业组）和业余足球守门员（业余组）各16名,共计32名被试。使用E-prime 3.0进行守门员点球方向判断实验,记录被试知觉预测的正确率和反应时。结果：基于先验信息进行知觉预测时,专业组守门员的知觉预测正确率显著高于业余组守门员。不同组别的反应时具有显著性差异,具体表现为在偏好一致（或不一致）的情况下,专业组的反应时都高于业余组。不同偏好条件下的正确率具有显著性差异,其中专业组被试在偏好不同的情况下具有显著性差异,业余组则无显著性差异。结论：与业余守门员相比,专业守门员在基于先验信息进行知觉预测时能更加准确地预判罚点球运动员的射门方向,即在知觉预测上存在专家优势。