Le pied plat valgus dynamique idiopathique est une déformation touchant un grand nombre d’enfants. Il fait l’objet de la plupart des consultations d’orthopédie pédiatrique et donne communément lieu au port d’orthèses plantaires correctives. Le pied étant un segment dont l’architecture lui confère des propriétés de souplesse et de robustesse, une altération de sa structure, en particulier touchant à la forme de la voute plantaire, peut engendrer des modifications de la marche. Les atteintes de cette déformation sont au cœur de beaucoup d’études mais la littérature reste toujours parcellaire et centrée sur quelques variables mesurées sur le membre inférieur. En revanche, s’il est important d’évaluer la déformation localement, la marche reste une coordination de l’ensemble des segments corporels hautement hiérarchisée, dont l’évaluation de la performance nécessite des analyses plus globales. Le travail de cette thèse s’attachera à effectuer une caractérisation de l’effet de la présence d’un pied plat valgus dynamique sur la marche de l’enfant, mêlant des méthodes issues de la biomécanique classique, aux analyses de données et aus théories des systèmes dynamiques non linéaires.Les principaux résultats de ce travail concernent la multiplicité des atteintes biomécanique et les nombreuses modifications que le pied plat valgus dynamique engendre au niveau musculaire et cinématique sur le membre inférieur. Les mouvements intrinsèques du pied s’avèrent refléter particulièrement le défaut de maitrise de la marche à l’échelle du patient. Enfin, le pied s’avèrera jouer un rôle protecteur du centre de masse vis-à-vis du maintien de la stabilité dynamique lors de la marche. / The pediatric flexible flat foot is a common deformation. It is the reason of most pediatric orthopedic consultations and commonly leads corrective foot orthotics prescription. The specific architecture of the normal foot gives it properties of adaptation, strength and flexibility. Any alteration of its structure, particularly related to the shape of the plantar arch can cause modifications in gait. A lot of studies investigated the effects of this deformation, but are generally centered on a small number of variables, only at the level of the lower limb. However, if the local deformation is important to assess, it is unlikely to represent the complex non-linear coordination of the whole body segments related to gait performance. This thesis aims at characterizing the effect of flexible flat foot on gait in children, from a biomechanical point of view at the lower limb level as well as at the global coordination level, using methods from classicla biomechanics, data analysis and non linear dynamical systems theories.The major outcomes of this work are the multiplicity of biomechanical effects and the numerous changes on muscles activities and kinematics of the lower limb caused by flexible flat foot. The intrinsic foot movements particularly reflect the lack of control of gait at the patient's level. The particular role of the trunk and contralateral leg regarding the specific locomotor pattern of patients will be detailed. Finally, the foot will appear to have a protective role of the center of mass concerning resistance to perturbations and maintaining gait dynamic stability.

Title: Neurophysiologic intervention induced changes of the functional foot characteristics in school children. Objectives: The aim of the research was to identify the functional characteristics of the foot in school children selected on the basis of the activity of physical activity in the highest intensity (sporting children) and in the lowest intensity (non-sporting children) and to find out possibilities of influencing the functional characteristics of the foot by targeted neurophysiological intervention. The whole research study was divided into 3 related parts, which were examined separately. The first study aim was an identification of group specific functional characteristics of the foot in 2 groups of school children - actively sporting children and non-sporting children. The second study aim was the influence determination of long-term duration high performance sport activity on the functional characteristics of the school children foot in adolescent elite soccer players. And the aim of the third study was to verify the effect of the targeted neurophysiologic active intervention on the functional foot characteristics in actively sporting children with foot dysfunction of pronated foot and/or flatfoot type. Methods: The research study was divided into three study parts consisted of...