Dans le cadre de cette recherche, nous avons étudié l'impact de la pratique de la gymnastique artistique et acrobatique sur le sens proprioceptif chez des sujets pré-adolescents gymnastes (pratiquant régulièrement la gymnastique) comparativement à des sujets non-gymnastes (ne pratiquant pas régulièrement cette activité). Une méthode de vibration du tendon d'Achille a été utilisée pour perturber l'information proprioceptive au cours du mouvement. L'impact de la perturbation proprioceptive a été évalué en fonction de l'expertise des sujets en gymnastique. Les sujets devaient réaliser deux tâches: une tâche statique de reproduction de mouvement de flexion dorsale et plantaire de la cheville ainsi qu'une tâche dynamique de marche, dans des conditions perturbées et non-perturbées. La précision du positionnement de la cheville dans l'espace et l'excursion angulaire au cours de la flexion dorsale et de la flexion plantaire étaient les mesures enregistrées. Les résultats en tâche statique ont démontré une tendance à l'erreur plus marquée chez les sujets gymnastes dans le positionnement final de la cheville dans l'espace. Les sujets gymnastes semblaient aussi davantage affectés par la vibration lors de la flexion dorsale de la cheville. Dans la tâche dynamique, les effets enregistrés étaient minimes. Cette étude démontre que la pratique de la gymnastique modifie l'utilisation du signal proprioceptif pour les mouvements de la cheville chez des pré-adolescents. Cet effet de la pratique semble se manifester davantage pour les mouvements de précision comme le positionnement dans l'espace. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Proprioception, Vibration, Gymnaste, Cheville, Éducation physique.

Reproduction de : Thèse de doctorat : Sciences et techniques des activités physiques et sportives : Poitiers : 2008. / Titre provenant de l'écran-titre. Bibliogr. 150 réf.

This thesis investigates the differential effects of muscle fatigue on center of pressure (COP) sway and associated central processes (attentional demands and sensory re-weighting) in older compared with young adults. More specifically, we first sought to determine whether the effect of muscle fatigue on unipedal stance was greater during a dual-task in older versus young adults, and second, to determine whether the effect of muscle fatigue on bipedal stance was greater in a condition with less reliable proprioceptive information in older versus young adults. Our main results show that with different muscle groups fatigued (ankle or hip) and postural tasks with varying difficulty (unipedal stance or bipedal stance on compliant surface), young adults increased their COP sway displacement and velocity with muscle fatigue, but not the associated attentional demands. When the central nervous system needed to increase the weight of the vestibular inputs due to sensory information being less reliable at the ankle joints from standing on a compliant surface (peripheral somatosensory information), COP sway displacement and velocity in young adults were greater with ankle muscle fatigue. We also found that healthy older adults were able to compensate for muscle fatigue just as well as young adults when visual information was available during a unipedal stance or when visual information was not available during a bipedal stance on a firm surface. However, when standing on a compliant surface, older adults showed a greater increase in COP sway displacement compared to young adults and increased attentional demands when visual information was not available during a bipedal stance. Our results suggest that healthy young and older adults are able to compensate for ankle muscle fatigue to limit postural control alterations during quiet standing under different conditions, and that the extent of postural control alterations largely depends on the tasks performed. The compensation strategies may be less efficient for older adults with less reliable proprioceptive information and without vision. Thus, a frailer group of older adults, with already reduced proprioception and/or reduced vision could possibly have more difficulty to efficiently use the same compensation strategies, and may be more at risk of falling when fatigued.

Osteoarthritis and ageing have been shown to induce changes in the number and health of peripheral mechanoreceptors. Whilst position and movement awareness in the osteoarthritic knee have been studied extensively, little work to date has been produced on muscle force awareness in this subject group. Poor force acuity may contribute to muscle and joint pain and dysfunction, and additionally hinder rehabilitation efforts in an osteoarthritic population. Overestimation of the muscles forces required for a given task, resulting in greater joint compression forces, may aggravate and inflame osteoarthritic symptoms. Underestimation of required muscle forces may amplify existing joint instability, increasing the risk of injury in an osteoarthritic population. Additionally, both under and overloading of muscles during the rehabilitation process can delay the return to full function after injury.When regarding the neurological process of force coding, current debate centres on the relative importance of centrally generated motor command mediated 'sense of effort' versus the peripheral mechanoreceptor signalled 'sense of tension' as the dominant coding process, with central mechanisms favoured in the majority of studies published to date. The purpose of this study was to investigate muscle force awareness in the knee extensors and flexors and hands of subjects with and without knee joint osteoarthritis. Twenty one subjects with knee joint osteoarthritis and 23 age and gender matched subjects with no known knee pathology were evaluated. All subjects performed ipsilateral isometric force estimation and force matching tasks, at levels scaled to individual maximum voluntary capacity (MVC). Errors in estimation and matching acuity were normalised to reference targets (comparison force/reference force) giving a relative score (RS) to allow comparison across submaximal force levels with RS less than 1.0 indicating that subjects produced insufficient force and vice versa.Maximal voluntary capacity tests revealed significantly lower (p<0.05) peak knee extension torque (111.2 Nm versus 145.3 Nm), but similar peak knee flexion torque (46.1 Nm versus 45.4 Nm for osteoarthritis and control subjects respectively). A pattern of overestimation at low reference levels and underestimation at high reference levels was demonstrated by all subjects. In the lower limb, force appreciation differed significantly between muscle groups regardless of knee condition, with knee extensors demonstrating greater overall accuracy than knee flexors. There was a significant difference (p<0.05) in force estimation ability and a trend to significance (p=0.066) for force matching acuity across groups at the 10% MVC test level. A significant (p<0.05) group difference in grip force estimation ability between the lowest and highest target levels was demonstrated.It can be concluded that there are small differences in force acuity in osteoarthritis subjects at lower submaximal force targets when compared to healthy age matched peers. The notion of information redundancy, whereby no new proprioceptive inputs, regardless of origin, are able to effect an improvement in force acuity in a given situation has been demonstrated in previous studies that reported relatively stable force matching acuity at forces between 30% and 60% of maximal capacity. The poor comparative force perception demonstrated in this study by the osteoarthritis group at the lower submaximal test levels supports the notion that centrally generated copies of motor commands do not provide sufficient data to adequately encode force magnitude at low levels of force generation, evoking a greater reliance data received from peripheral mechanoreceptors. This has significant implications for this subject group given that the majority of daily tasks require only low levels of force generation. Given that perceptive acuity in a variety of sensory modalities has been shown to improve with training there may be a role for force perception training in older adults with osteoarthritis.

Thesis (M.S.)--West Virginia University, 2005 / Title from document title page. Document formatted into pages; contains vi, 101 p. : ill. (some col.). Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--University of Cape Town, 2003. / Includes bibliographical references (leaves 284-287). Also available online (PDF file) by a subscription to the set or by purchasing the individual file.

Thesis (M. Med. Sc.)--University of Hong Kong, 2005. / Also available in print.

Thesis (Ph. D.)--University of Cape Town, 2003. / Includes bibliographical references (leaves 284-287).

Thesis (M.S.)--Indiana University, 2002. / Includes bibliographical references (leaves 77-84).

Thesis (M.S.)--Indiana University, 2005. / Includes bibliographical references.