Estudos anteriores indicam que a obesidade afeta negativamente o tempo de movimento em tarefas que exigem velocidade e precisão, especificamente quando essas tarefas são realizadas em pé. Entretanto, nenhum estudo investigou se esse efeito negativo se estende para a precisão do movimento, dado que nesses estudos apenas as tentativas corretas foram analisadas, ou seja, a magnitude do erro não foi considerada. Deste modo, o objetivo do presente estudo foi investigar o efeito de duas posições corporais, em pé e sentado, na precisão de uma tarefa de apontar em obesos e eutróficos. Para tal, foram analisados o Tempo de Movimento (TM), o Erro Radial (ER) e o Tempo de Preparação (TP), além da quantidade de movimentos finalizados dentro do alvo, para cada grupo, alvo e posição corporal. Participaram do estudo 42 mulheres distribuídas em dois grupos de acordo com o índice de massa corporal (IMC): obesas (OB, IMC = 37,4 + 5,9 kg/m2,) e eutróficas (EU, IMC = 22,2 + 2,1 kg/m2). A tarefa consistiu em levar um cursor circular, apresentado em um monitor LCD, da posição inicial até o centro de um alvo o mais rápido e preciso possível, por meio do deslocamento de um stylus sobre uma mesa digitalizadora. Foram utilizadas quatro larguras de alvos (0,5 cm, 1,0 cm, 2,5 cm e 5 cm de diâmetro), apresentados a uma distância de 39,5 cm da posição inicial do cursor, correspondendo a um movimento de 25,5 cm na mesa digitalizadora. A tarefa foi executada em pé e sentado. Para cada tamanho de alvo foram realizadas 15 tentativas em cada posição corporal, somando um total de 120 tentativas por participante (4 tamanhos de alvo x 15 tentativas x 2 posições corporais). Os resultados revelaram que o grupo OB apresentou maior TM e menor ER em pé em relação à sentado. Por sua vez, o grupo EU apresentou TM e ER similares em ambas as posições corporais. Adicionalmente, nenhum dos grupos apresentou efeito da posição corporal no TP e o número de tentativas finalizadas dentro do alvo foi similar entre as posições corporais em ambos os grupos. Portanto, a posição corporal afeta o TM e a precisão do apontar de mulheres obesas, efeito não observado em mulheres eutróficas, indicando que a obesidade afeta negativamente a qualidade de movimentos que exigem velocidade e precisão quando realizados em pé / Previous research has shown that obesity adversely affects movement time in tasks that require speed and accuracy, specifically when these tasks are performed in a standing position. Nevertheless, no research has shown whether this negative effect extends to the accuracy of the movement, since only correct trials were analyzed, i.e., error magnitude was not considered. This study sought to determine the effect of two body positions, standing upright and seated, on the precision of discrete aiming, in obese and normal weight adults. To investigate this issue, Movement Time (MT), Radial Error (RE) and Preparation Time (PT) were analyzed, as well as the number of movements completed within the target, for each group, in each target and body position. Forty-two women were distributed in two groups according to their Body Mass Index (BMI): obese (OB, BMI = 37.4 + 5.9 kg/m2) and normal weight (EU, BMI = 22.2 + 2.1 kg/m2). The task goal consisted of moving a circular cursor, showed on a LCD monitor, from the starting position to the center of a target as quickly and accurately as possible, by moving a hand-held stylus on a digitizing tablet. There was four possible target diameters (0.5 cm, 1.0 cm, 2.5 cm and 5 cm), presented 39,5 cm from the cursor initial position, which corresponded to a 25,5 cm displacement of the stylus on the tablet. Participants performed the task in seated and standing upright body positions. For each target size, participants performed 15 trials in each body position (4 target sizes x 15 trials x 2 body positions - 120 total). The OB group showed higher MT and lower RE while standing upright, compared to seated. In turn, the EU group showed similar MT and RE, regardless of body position. In addition, none of the groups showed any effect of body position on PT or on the number of completed trials within the target. Therefore, body position affects both MT and accuracy of obese women in a discrete aiming task, opposed to what was observed for normal weight women, indicating that obesity adversely affects the quality of movements that require speed and accuracy when they are performed in a standing upright position

Time-optimal solutions provide us with the fastest means to regulate a system in presence of input constraints. This advantage of time-optimal control solutions is offset by the fact that their real-time implementation involves computationally intensive iterative techniques. Moreover, time-optimal controls depend on the initial state and have to be recalculated for even the slightest perturbation. Clearly time-optimal controls are not good candidates for online regulation. Consequently, the search for alternatives to time-optimal solutions is a very active area of research. The work described here is inspired by the simplicity of optimal-aim concept. The "optimal-aim strategies" provide online regulation in presence of bounded inputs with minimal computational effort. These are based purely on state-space geometry of the plant and are inherently adaptive in nature. Optimal-aim techniques involve aiming of trajectory derivative (or the state velocity vector) so as to approach the equilibrium state in the best possible manner. This thesis documents the efforts to develop an online regulation algorithm for systems with input constraints. Through a number of hypotheses focussed on trying to reproduce the exact time-optimal solution, the diffculty associated with this task is demonstrated. A modification of optimal-aim concept is employed to develop a novel regulation algorithm. In this algorithm, aim directions are chosen in a special manner to generate the time-optimal control approximately. The control scheme thus developed is shown to be globally stabilizing for systems having eigenvalues in the CLHP (closed left half-plane). It is expected that this method or its modifications can be extended to higher dimensional systems as a part of future research. An alternative control algorithm involving a simple state-space aiming concept is also developed and discussed.

Two studies were devised to determine why the difference in manual aiming performance, between full vision and no vision, is decreased for a randomized visual feedback schedule. In study one, aiming accuracy and precision was assessed for up to four trials in the same vision condition, following a switch in visual feedback availability. In experiment one, visual feedback availability was uncertain; while in experiment two, certainty was provided. Results of both experiments revealed that the precision of the first trial immediately following the switch in visual condition was reminiscent of the trial that preceded it, even when performed under different visual conditions. For study two, the inter-trial interval was evaluated by extending the interval to five seconds. Results indicated no reminiscence effect. Overall, we suggest that when the inter-trial trial is brief, individuals rely on offline visual information from the preceding trial to plan the subsequent movement, regardless of certainty.

Two studies were devised to determine why the difference in manual aiming performance, between full vision and no vision, is decreased for a randomized visual feedback schedule. In study one, aiming accuracy and precision was assessed for up to four trials in the same vision condition, following a switch in visual feedback availability. In experiment one, visual feedback availability was uncertain; while in experiment two, certainty was provided. Results of both experiments revealed that the precision of the first trial immediately following the switch in visual condition was reminiscent of the trial that preceded it, even when performed under different visual conditions. For study two, the inter-trial interval was evaluated by extending the interval to five seconds. Results indicated no reminiscence effect. Overall, we suggest that when the inter-trial trial is brief, individuals rely on offline visual information from the preceding trial to plan the subsequent movement, regardless of certainty.

Time-optimal solutions provide us with the fastest means to regulate a system in presence of input constraints. This advantage of time-optimal control solutions is offset by the fact that their real-time implementation involves computationally intensive iterative techniques. Moreover, time-optimal controls depend on the initial state and have to be recalculated for even the slightest perturbation. Clearly time-optimal controls are not good candidates for online regulation. Consequently, the search for alternatives to time-optimal solutions is a very active area of research. The work described here is inspired by the simplicity of optimal-aim concept. The "optimal-aim strategies" provide online regulation in presence of bounded inputs with minimal computational effort. These are based purely on state-space geometry of the plant and are inherently adaptive in nature. Optimal-aim techniques involve aiming of trajectory derivative (or the state velocity vector) so as to approach the equilibrium state in the best possible manner. This thesis documents the efforts to develop an online regulation algorithm for systems with input constraints. Through a number of hypotheses focussed on trying to reproduce the exact time-optimal solution, the diffculty associated with this task is demonstrated. A modification of optimal-aim concept is employed to develop a novel regulation algorithm. In this algorithm, aim directions are chosen in a special manner to generate the time-optimal control approximately. The control scheme thus developed is shown to be globally stabilizing for systems having eigenvalues in the CLHP (closed left half-plane). It is expected that this method or its modifications can be extended to higher dimensional systems as a part of future research. An alternative control algorithm involving a simple state-space aiming concept is also developed and discussed.

AbstractThe aim of this study is to illustrate, discuss and problematize goal-aiming in preschool practice. The study focus on the didactic work of preschool teachers, at a practice action level that includes planning and action. The study could be considered important in times of changes in the context of preschool education with high expectations on the performance of preschools and preschool teachers. The process has been explorative with a hermeneutic approach and the result of the study has emerged in the interaction between preunderstanding, data, theories and new understanding.The study has a critical didactic approach with focus on what may occur as multiple understandings of curriculum goal aiming at a practice action level. The data consist of seven preschool teachers’ narratives about their goal aiming work and the research questions are: •Which different ways to do goal-aiming at a didactic action level occurs in the narratives of preschool teachers?•Which different aspects of complexity in relation to goal-aiming occurs in the narratives of preschool teachers?•Which different norm didactic and critical didactic ideas about goal-aiming occurs in the narratives of preschool teachers?Four different ways of goal-aiming occurs at a didactic action level: pre goal-aiming, post goal-aiming, present goal-aiming, child goal-aiming and environmental goal-aiming. The goal-aiming actions can be understood in the form of a process and emerge like goal-aiming chains.Three different complexity aspects are identified: goal-complexity, learning-complexity and individual-complexity and are being discussed in the result chapter.Norm didactic ideas and critical didactic ideas emerge from the narratives at the same time, which can be understood as multiple understanding. The norm didactic believes emerge in the context of evaluation and the critical didactic believes emerge in goal- aiming action level considering planning and teaching.

No description available.

Football penalty kicks are having increasing influence in today’s professional game. Despite this, little scientific evidence currently exists to ascertain the mechanisms behind performance failure in this task and/or the efficacy of training designed to improve penalty shooting. In a football penalty kick it has been reported that the majority of kickers do not look to the area they wish to place the ball; preferring to focus on the ‘keeper and predict anticipatory movements before shooting. Such a strategy seems counterproductive and contradictory to current research findings regarding visually guided aiming. Coordination of eye and limb movements has been shown to be essential for the production of accurate motor responses. A disruption to this coordination not only seems to negatively affect performance, but subsequent motor responses seem to follow direction of gaze. Thus, where the eyes lead actions tend to follow. In study 1, ten participants were asked to kick a standard sized football to alternate corners of a goal, whilst looking centrally and whilst looking where they intended to hit. This disruption of eye-limb coordination brought about a 15% reduction in kicking accuracy. When participants were asked to fixate centrally, their shots hit more centrally (17cm) than when they were allowed to look where they intended to hit. These results were in spite of no significant differences between the number of missed shots, preparation time and ball speed data across conditions. We concluded that centrally focused fixations dragged resultant motor actions inwards towards more central target locations. Put simply, where the eyes looked shots tended to follow. The second study sought to test the predictions of attentional control theory (ACT) in a sporting environment in order to establish how anxiety affects performance in penalty kicks. Fourteen experienced footballers took penalty kicks under low- and high-threat counterbalanced conditions while wearing a gaze registration system. Fixations to target locations (goalkeeper and goal area) were determined using frame-by-frame analysis. When anxious, footballers made faster first fixations and fixated for significantly longer toward the goalkeeper. This disruption in gaze behaviour brought about significant reductions in shooting accuracy, with shots becoming significantly centralized and within the goalkeeper’s reach. These findings support the predictions of ACT, as anxious participants were more likely to focus on the “threatening” goalkeeper, owing to an increased influence of the stimulus-driven attentional control system. A further prediction of ACT is that when anxious, performers are more likely to be distracted, particularly if the distracter is threat related. When facing penalty kicks in football (soccer), goalkeepers frequently incorporate strategies that are designed to distract the kicker. However, no direct empirical evidence exists to ascertain what effect such visual distractions have on the attentional control, and performance, of footballers. In the third study, eighteen experienced footballers took five penalty kicks under counterbalanced conditions of threat (low vs. high) and goalkeeper movement (stationary vs. waving arms) while wearing eye-tracking equipment. Results suggested that participants were more distracted by a moving goalkeeper than a stationary one and struggled to disengage from a moving goalkeeper under situations of high threat. Significantly more penalties were saved on trials when the goalkeeper was moving and shots were also generally hit closer to the goalkeeper (centrally) on these trials. The results provide partial support for the predictions of attentional control theory and implications for kickers and goalkeepers are discussed. The previous studies showed that anxiety can disrupt visual attention, visuomotor control and subsequent shot location in penalty kicks. However, optimal visual attention has been trained in other far aiming skills, improving performance and resistance to pressure. In study 4, we therefore asked a team of ten university soccer players to follow a quiet eye (QE; Vickers, 1996) training program, designed to align gaze with aiming intention to optimal scoring zones, over a seven week period. Performance and gaze parameters were compared to a placebo group (ten players) who received no instruction, but practiced the same number of penalty kicks over the same time frame. Results from a retention test indicated that the QE trained group had more effective visual attentional control; were significantly more accurate; and had 50% fewer shots saved by the goalkeeper than the placebo group. Both groups then competed in a penalty shootout to explore the influence of anxiety on attentional control and shooting accuracy. Under the pressure of the shootout the QE trained group failed to maintain their accuracy advantage, despite maintaining more distal aiming fixations of longer duration. The results therefore provide only partial support for the effectiveness of brief QE training interventions for experienced performers. This series of studies are the first to explore the gaze behaviour of football penalty takers in a quest to uncover and understand anxiety’s negative influence on attentional control and performance. They are also the first to explore the efficacy of goalkeeper distractions and training in improving performance from both the goalkeeper’s and kicker’s perspective. The results of these studies conclude that when anxious, penalty takers show an attentional bias toward the ‘threatening’ goalkeeper that can be increased and utilised by a goalkeeper employing distraction techniques and that penalty takers do benefit, to some extent, from a gaze-based pre-shot routine

Title Impact of gear and weaponry on posture in kneeling shooting position Objectives The aim of this thesis is to find out the impact of gear and weaponry on posture in the kneeling shooting position. Specifically, this study examines the influence of carried load on posture, aiming stability and balance in the high and low kneeling shooting position variants. Methods This thesis has an empirical observational character. The shooting position was tested by Qualisys camera system and Kistler pressure plates. The measurment was performed on 16 Military department students with mean age of 23 years (standard deviation 2,63 years). Measurements were carried out in four levels, with no load, light load of 15 kg, mean load of 30 kg and heavy load of 45 kg. The measurement was performed on high kneeling variant and the low variant with elbow supported by the front knee. Intra-individual comparison of the results of each level was determined by a T-test. Results: The load in a form of gear and weapony had a statisicaly significant - negative influence on the kneeling shooting position posture. Gear and weaponry used for this study caused a lower trunk position, increased shoulders angle in the low variant, lesser aiming stability and balance control in the position. The bigger was the weight of gear and...

Les objectifs de notre travail étaient : (i) de proposer un nouveau cadre conceptuel pour l’entraînement bimanuel chez les patients hémiplégiques (ii) de concevoir et tester une nouvelle approche de rééducation basée sur l’équilibre entre les différentes contraintes. Afin d’atteindre ces objectifs, nous avons adopté une approche du type preuve-de-concept.La première partie de ce document est consacrée à une revue critique de la littérature. La deuxième partie présente le travail expérimental qui était mené pour explorer ce concept, chez des sujets sains et des patients hémiparétiques. La première étude a exploré le comportement unimanuel dans une tâche de pointage discret pour une large gamme de d’indices de difficulté (ID). Dans la seconde étude, nous avons exploré l’effet de l’asymétrie bimanuelle induite par la tâche sur l’expression du couplage. La troisième étude aborde la problématique des asymétries induites par l’AVC et par la tâche chez des patients soufrant de déficits plus ou moins graves. Globalement, les résultats expérimentaux ont corroboré nos hypothèses initiales. Ainsi, ils nous ont permis de concevoir une nouvelle stratégie de rééducation bimanuelle. Cette stratégie de rééducation, avec le protocole de recherche clinique en cours, ont été présentés dans la troisième partie de la thèse. Notre approche a fourni une preuve de concept sur l’importance de l’équilibre entre couplage et rupture de symétrie dans le comportement bimanuel du patient hémiplégique. Elle a permis également d’envisager la manière dont les asymétries devraient être prises en compte dans la rééducation. Les perspectives futures ont été discutées dans la dernière partie du manuscrit. / In the present work we aimed at: (i) setting new conceptual foundations for bimanual movement training in stroke, and (ii) providing practical guidelines to appropriately design and test a comprehensive constraint-led bimanual rehabilitation strategy. In order to achieve these stated objectives, we adopted a proof-of-concept approach.The first part of the current manuscript includes a critical review of BMT literature on the basis of the theoretical principles and empirical findings of the dynamical systems approach. The second part reports the experimental work that was conducted to investigate this concept in healthy and in hemiparetic subjects. The first study investigated unimanual discrete rapid aiming, under different task conditions and for a wide range ID values. In the second study, the effect of task-induced inter-limb asymmetry on the expression of bimanual coupling was explored. The third study, addressed the issue of task- and stroke-induced asymmetries in patients with different degrees of impairments. Overall, experimental findings corroborated our initial hypotheses. It permitted the design of a new BMT strategy to (re)train stroke patient. This rehabilitation strategy and the on-going clinical protocol were presented in the third part of the thesis.Though voluntarily qualitative, our approach provided a preliminary proof of concept on how CVA- and task-induced inter-limb asymmetries should be taken into account in rehabilitation. The conclusions of our work along with the opened perspectives were discussed at the end of the manuscript.