The aim of this study was to investigate the influence of the goalkeeper as an outfield player on defensive subsystems in the team sport of futsal. For this purpose, all sequences of play involving the goalkeeper (n = 65), and the sequences without a goalkeeper (controls) (n = 11), were selected from digital video footage of a futsal competition, and analysed using TACTO software. The defensive area, attacker-defender distance, and interception distance were used to examine players' coordination tendencies as a team in completion of successful and unsuccessful passes and shots. Results showed that each team reduced its defensive area as well as its variability in situations where the goalkeeper acted as an outfield player. This finding implies that it was an effective defensive strategy because it led to emergence of more unsuccessful passes. It was also observed that the goalkeeper acting as an outfield player was an effective strategy for attacking in terms of increasing shots at goal.
RESUMOUm aspecto fundamental do sistema visual que subsidia a aquisição de informação relevante para o controle postural de bailarinas, o movimento dos olhos e da cabeça, foi investigado durante a execução da pirouette, um giro do ballet clássico. Oito bailarinas experientes foram analisadas com (olhos abertos normalmente) e sem (olhos vendados) informação visual disponível, com o objetivo de (i) testar a hipótese de associação entre maior duração da fixação do olhar antes do início do giro e melhor performance motora, (ii) averiguar a validade de dicas dos instrutores de ballet sobre como "marcar a cabeça", e (iii) verificar o efeito da disponibilidade de informação visual no controle postural das bailarinas. Os resultados não corroboraram a hipótese de alta correlação negativa entre duração da fixação inicial e instabilidade postural, mas revelaram longos períodos de fixação antes do giro e reduzidas oscilações corporais. A indisponibilidade de informação visual deteriorou significativamente a estabilidade postural. Um nítido sequenciamento dos giros do tronco, cabeça e olhar foi observado, mostrando a pertinência das dicas dos instrutores de ballet.Palavras-chave: informação visual, comportamento do olhar, controle postural, ballet ABSTRACT Visual information and postural control during pirouette execution in balletA fundamental aspect of the visual system that supports visual information acquisition relevant to postural control of ballet dancers, eyes and head movements, was investigated during the execution of a pirouette, a turn of classical ballet. Eight expert ballet dancers were analyzed with (opened eyes) and without (blindfolded eyes) visual information available in order to (i) test the hypothesis of association between longer gaze fixation turn initiation and better motor performance, (ii) check the validity of ballet instructors' cues on how to "set the head", and (iii) verify the effect of availability of visual information on postural control of ballet dancers. The results did not corroborate the hypothesis of high negative correlation between initial fixation duration and postural instability, but they revealed long initial fixation durations and reduced body oscillations. The unavailability of visual information deteriorated significantly the postural stability. A clear sequence of trunk, head and gaze turns was observed, showing the adequacy of ballet instructors' cues. Key-words: visual information, gaze behavior, postural control, balletRev Port Cien Desp 8(2) 241-250
The aim of this study was to investigate the volleyball setter's decisionmaking on tipping, based on spatiotemporal variables of interaction between players and between players and the game environment. The sample consisted of 172 sequences of 20 volleyball games from 6 male and 10 female teams. The actions selected for analysis were 86 tips and 86 sets (control group), both made by the setters. From the players' x and y coordinates of displacement trajectory, 37 spatiotemporal measures of players' interaction were calculated as dependent variables, which were analysed by multivariate analysis of variance. Results showed that tips and sets differed in terms of (i) final area between opponents, (ii) displacement of setter to reach the ball, (iii) displacement velocity of setter to reach the ball, (iv) distance between setter and net in the initial moment, (v) distance between setter and net in the final moment, (vi) pass velocity and (vii) final distance between setter and blockers. It was concluded that these variables formed a spatiotemporal configuration of the game that influenced the setter's decision-making on tipping.
This study investigated how changes in the focus of instruction might affect the learning by individuals who are not trained dancers of a complex classical ballet movement, the pirouette. Seventy-two volunteer college students were divided into six groups according to the focus of instruction: (1.) head, (2.) arms, (3.) trunk, (4.) knees, (5.) feet, and (6.) controls. In the acquisition phase, all groups performed 160 trials, over 2 consecutive days. At the beginning of each day, they received verbal instruction regarding some of the general principles involved in performance of the pirouette and viewed a video that illustrated those principles. Each group (head, arms, etc., exclusive of controls) was then given specific directions for controlling focus on its body part while performing the movement. After a week, all participants were asked to complete a retention test, with no additional instruction. The trials were videotaped with two cameras (frontally and laterally), and the results were analyzed by 10 specially trained examiners, utilizing Movement Pattern and Error of Performance measures. They revealed that all groups improved in the acquisition phase, and the improvement was maintained in the retention test. No differences were revealed between groups. It was concluded that generalized instruction in basic principles of the movement was more effective than focus on specific body parts in the teaching and learning of the pirouette.
Summary.-The aim of this study was to compare the learning process of a highly complex ballet skill following demonstrations of point-light and video models. 16 participants divided into point-light and video groups (nȶƽȶŞǼȱȱŗŜŖȱ ȱȱȱĴǰȱ¢ȱȱȱȱȱŘŖȱǰȱȱȱȱ demonstration and practice, with a retention test a day later. Measures of head and trunk oscillation, coordination disparity from the model, and movement time difference showed similarities between video and point-light groups; ballet experts' evaluations indicated superiority of performance in the video over the point-light ǯȱ ȱ ȱ ȱ ȱ ȱ ȱ ȱ ȱ ȱ ȱ ȱ ȱȱȱȱ ǰȱȱȱȱ¢ȱȱĜ¢ȱȱ higher relevance of information contained in biological motion models applied to learning of complex motor skills.Perceiving other persons' actions, emotions, and intentions is a very ȱȱǻ ȱǭȱěǰȱŘŖŖŝǼǯȱȱȱȱȱȱ human movement, one of the aspects necessary to observational learning ǻ ǰȱ ǰȱ¢ǰȱǰȱǭȱ ǰȱŘŖŖŝǼǯȱȱȱȱ-ȱ ȱ ȱ ȱ ȱ ȱ ȱ ȱ ǰȱ ¢ȱ -serving others, into motor commands to reproduce the observed behavior ǻǰȱǰȱ¢ǰȱǭȱ ǰȱŘŖŖŝǼǯ ȱȱȱȱȱȱǰȱȱȱȱȱȱ body segments in a new and functionally integrated manner. Important visual information available to the learner when observing others' activity ȱȱȱȱȱȱȱȱ¢ȱǻ¢ȱǭȱ ǰȱŗşŞśǼǯȱ-cations of information regarding this relative motion are stronger in the initial stage of motor learning than in the more advanced ones (Newell, ŗşŞśǼǯ 1 Address correspondence to Sérgio Tosi Rodrigues, Laboratory of Information, Vision, and ȱǻ Ǽǰȱ ǯȱȱ¢ȱ ǰȱȱ¢ȱȱ¨ȱȱǻ Ǽǰȱ ǯȱLuis ȱ ħȱ ǰȱŗŚȬŖŗȮȱǰȱ ȱŗŝŖřřȬřŜŖǰȱ ǰȱǰȱ £ȱȱȬȱ ǻȓǯǯǼǯ 2 This study was supported by scholarships to M. C. Ferracioli (Programa Institucional de ȱȱ³¨ȱ Çęȱȱ ȱȱȱ ȱ Çęȱȱ-àǰȱ £Ǽȱȱǯȱ ǯȱ ȱǻ ³¨ȱȱ ȱ¥ȱȱȱ ȱȱ¨ȱ-ǰȱ £ȮȱǛŖŚȦŗŖŗşřȬŗǼȱȱȱȱȱǻ ³¨ȱȱȱ ȱ ȱȮȱǛŖŖşŖȦŗŖȬ ǼǯȱThe authors would like to thank M.Sc. Rodrigo Carvalho ǻ ·ȱ·ȱȱȃȱȱ¤ǰȄȱ¨ȱȱȱ¢ǰȱ ǰȱ £Ǽȱ for his technical support on constructing the video models, and Mrs. Marina Denardi for revising the manuscript.
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