The purpose of the current research was to examine how a novel balance task is learnt by individuals with a mature neurological system, and to investigate the responses of experienced hand balancers to mechanical and sensory perturbations. Balance in each posture was assessed by various techniques, including: traditional measures of centre of pressure, nonlinear time series analysis of centre of pressure, estimates of feedback time delay from cross correlations and delayed regression models, and calculation of small, medium, and large movement corrections. Data from this study suggests that the best balance metric for distinguishing between each of the balance conditions was the traditional balance measure of sway velocity. However, sway velocity cannot provide any further information on the underlying process of balance. Nonlinear measures of balance offer insight into the underlying deterministic processes that control balance, offering measures of system determinism, complexity, and predictability. Assessments of feedback time delay and movement corrections provide both an insight into the control of posture and help distinguish one condition from another. Both feedback time delay and movement corrections and magnitudes may be used simultaneously to delve further into the control of posture. Delayed regression models seem to be an appropriate and useful tool for estimating feedback time delays during balance. Findings support the use of the third term in the adapted regression model as a means of estimating the effect of passive stiffness on feedback time delay. Generally, with increased duration in handstand subjects displayed reduced sway as measured by traditional measures of balance. A more marked change in nonlinear measures of balance can be seen, with quicker reductions in variance for some nonlinear measures of balance than in the traditional measures. It may be that more pronounced changes in nonlinear measures represent changes in the subjects underlying process of postural control, whereas less pronounced changes in traditional measures relate more to their general ability or performance in the balance task.

Training aids can play an important role in the training of athletes, but only if they assist in the learning of correct technique. The design of a training aid differs considerably from the design of other products because it is crucial that the mechanisms used in learning a skill must be taken into consideration. Research has shown that this can be achieved by: encouraging specific motor skills, providing feedback, providing support in a safe environment, permitting repetition, permitting progressive learning, or by providing some combination of these. For this to be possible an in-depth understanding of the biomechanical requirements of the sporting activity is essential. A study was carried out to determine the fundamental requirements of a training aid, and to then design and build two working prototype gymnastics training aids. Elite training sessions were observed and High Performance coaches were interviewed to establish the skills that required a training aid and the customer requirements for such a device. On the basis of this information two contrasting gymnastics skills were chosen. The first was a handstand on the rings, a complex motor control skill requiring the gymnast to balance on two moving pendulums, requested by 100% of the coaches interviewed. The second skill was a backward handspring, often the first backward dynamic skill most gymnasts will learn, requested by 89% of the coaches interviewed. The training aids were required to simplify the learning of the skill, whilst still utilising correct technique. The backward handspring aid was also required to effectively support the gymnast but not obstruct a good performance. A biomechanical analysis of each skill was carried out in order to inform the design of suitable training aids. The aids were designed and manufactured in accordance with British Standards, and were then biomechanically assessed to ensure that they correctly aided the learning of the skills. In order to assess the aids: displacement, force and muscle activation data were collected and were used to compare the gymnastics skills with and without the aids. The data showed that the training aids replicated the correct biomechanical requirements of the actual skills: the handstand aid was shown to utilise the same control mechanism as was observed on the rings, and the backward handspring aid permitted a unobstructed good performance and assisted in the learning of the skills with correct technique. Both aids were also demonstrated to out-perform any of the existing training aids.

Cette thèse s'attache à décrire et à comprendre l’activité didactique conjointe de trois enseignants d’EPS et de leurs élèves dans l’enseignement de la gymnastique en Tunisie. Elle a pour objectif de déterminer l’influence de l’expertise et de l’expérience sur la mise en scène et la régulation des situations didactiques. Afin de disposer d’une pluralité de questionnements susceptibles d’éclairer au mieux la complexité de la réalité observée, elle prend appui sur les principaux concepts de la Théorie de l’Action Conjointe en Didactique. Trois cycles d’enseignement portant sur l’enseignement de l’appui tendu renversé-roulade ont été observés. Le recours à une méthode dite « clinique/expérimentale » a permis de créer les conditions de la comparaison inter-cas afin d’analyser dans le détail les interactions didactiques en lien avec l’expérience professionnelle des trois enseignants et selon leur degré d’expertise gymnique. Leurs activités didactiques ont été décrites à partir de l'enregistrement audio et vidéo de séances et de données d'entretiens (ante cycle, ante séance et post séance). Les résultats mettent en évidence les effets conjugués de l’expertise dans l’APS et de l’expérience professionnelle sur l’épistémologie pratique des professeurs. Il ressort de l’analyse comparative que l’expérience professionnelle et l’expertise dans l’APS ont une incidence sur les types de ruptures et/ou de micro-dysfonctionnements observés, rendant compte ainsi du «travail» souterrain du contrat didactique dans ses aspects différentiels en lien avec les positions de genre et les hiérarchies d’excellence des élèves. La recherche confirme que l’épistémologie pratique du professeur est un déterminant du fonctionnement du système didactique. Elle met par ailleurs en évidence que l’expérience et l’expertise professionnelles peuvent expliquer en partie les manières dont les élèves de sexe et de niveaux d’habiletés gymniques différents tirent ou non profit de l’enseignement qui leur est dispensé. / This thesis focuses to describe and understand the joint didactic activity of three physical education teachers and their pupils in gymnastic learning in Tunisia. It aims to determine the expertise and experience influence on the implementation and the regulation of didactic situations. In order to illuminate the complexity of the observed reality, this thesis is based on the main concepts of the Theory of Joint Action in Didactic. In this context, three teaching units about learning handstand - roll were observed using a method called "clinical/experimental" This method has created the conditions for cross case studies to analyze in detail the didactic interactions related to the educational experience of three teachers and according to their expertise in gymnastics. Their didactic activities have been described from the videotapes of the lessons and interviews data (pre-unit, pre-lesson and post-lesson individual interviews with the teachers). The results highlight the combined effects of the expertise and the teaching experience on the teachers’ practical epistemology. It appears from the comparative analysis that the teacher professional experience and expertise in the specific physical activity have an impact on the observed types of breach and/or micro-dysfunction, reflecting the “underground work" of the didactic contract in its differential aspects in relation to pupils’ gender positions and pupils’ hierarchies of excellence. Research confirms that the teacher’s practical epistemology determines the functioning of the didactic system. It is also shown that teaching experience and expertise may partly explain the ways in which pupils (having different gender positions or gymnastic skill levels) take or not benefit of the education they are provided.

La contribution relative des différentes entrées sensorielles dans le contrôle postural a souvent été étudiée dans le cadre de la posture érigée fondamentale. L’objectif de nos travaux a été de déterminer cette contribution dans deux postures relativement proches dans leur configuration : l’appui tendu renversé (ATR) et la verticale inversée (VI) en milieu aquatique. Si la vision est souvent considérée comme information principale dans le contrôle postural de la station érigée, la configuration structurelle (champ visuel restreint en ATR, immersion de l’œil en VI) de ces deux postures laisse imaginer un fonctionnement différent. La perturbation des différents capteurs sensoriels impliqués dans le contrôle postural a permis d’observer la réorganisation mise en place par le système nerveux central (SNC) pour y remédier. De plus la prise en compte d’un facteur perceptif comme la dépendance au champ visuel nous a paru être un élément pertinent pour tenter d’observer d’éventuelles différences interindividuelles dans les comportements des sujets. La perturbation du contrôle postural a été évaluée au travers d’une analyse cinématique et d’une analyse stabilométrique de l’ATR (analyse classique et non-linéaire). Les résultats de ces analyses laissent entrevoir des différences de stratégie entre les sujets dépendants et indépendants au champ visuel dans le contrôle de l’appui tendu renversé, ce qui ne semble pas être le cas en verticale inversée / The relative contribution of the different sensory inputs in erect postural control has often been studied. The aim of this work is to determine this contribution in two positions relatively close in their configuration: the handstand and the upside-down posture in water. If vision is often considered as the main information in postural control, the structural configuration (restricted visual field in handstand, eye’s immersion in upside-down posture) of these two postures lets imagine a different operation. Disruption of sensory receptors involved in postural control has allowed observing the reorganization implemented by the central nervous system (CNS). In addition, the visual field dependence appeared to be a relevant factor to observe interindividual behavioral differences. Disturbance of postural control was assessed through a kinematic analysis and a stabilometric analysis of the handstand (classical analysis and non-linear analysis). Results of these analyzes suggest different strategy according to visual field dependence in the control of the handstand, which does not seem to be the case in upside-down posture