The main objective of this work is to address the growing concern of balance loss and falls in the aging population. The initial aspect looks at balance control in a dynamic environment. Observation of age and gender influence on motor control will be made related to a new dynamic balance testing platform (DBTP). The topic of focus in the second portion relates to reaction time in an unstable environment. Research has found that balance improves when physical activity is a part of daily life for seniors. Physical activity influence on reaction time will be investigated with a new approach to exercise classes for seniors. Finally, an understanding of motor control and balance may be acquired and physical activity incorporated into the life of an elderly individual, however this will never fully prevent falls from taking place. A novel approach to injury prevention due to falls is explored in the final portion of this thesis. Study One - Using a newly constructed dynamic balance testing platform (DBTP), balance ability of three age groups was observed in two visual conditions and in relation to gender. Center of Gravity excursion (COGex) was observed to determine the differences between age groups and gender. Platform response patterns were also observed to asses the functionality of the DBTP as a new tool for balance testing. Three things were found: 1) Age differencesrelated to platform movement suggested that balance decreased with age in both visual conditions. 2) Gender differences between COGex found that males covered the most distance in both visual conditions when compared to females. 3) Gender differences between platform characteristics showed that females balanced longer and had lower platform movement rate than males, in both visual conditions. In order to consider the DBTP as a new tool for determination of balance ability, more refined tests are necessary. Study Two - Using pre- and post-training tests, the effects of a Fitball® exercise program on performance in eight subjects was documented. The exercise program focused on improving dynamic balance and postural stability of seniors. To evaluate progress-related changes, pre and post-tests in a dynamic environment were applied. Center of gravity (COG) excursion, catch success rate, and balance success rate were quantified, and synchronized data collection of 3D motion capture (VICON v8i) and ground reaction force (2 KISTLER platforms) was analyzed. During pre- and post-tests, participants stood in a walk-like stance and were asked to catch a weighted ball, which dropped unexpectedly. Results showed no significant changes in balance success rate. Significant improvements were found, however, in both COG control and catch success rate following training (p 0.05). Study Three - Falls in the elderly are inevitable so it is necessary to take precautions. This study looks at falls in relation to velocity characteristics of various locations on the trunk, and contrasts them to activities of daily living (ADL) in 13 individuals. A threshold level was established to be 2.0m/s, a value that exceeded all maximum resultant velocities for ADL, but was superseded by all fall activity resultant velocities. This suggests that a life vest, which responds similar to a vehicle airbag, may be created and worn that will deploy past a threshold of 2.0m/s with the incidence of a fall. / xiii, 91 leaves : ill. ; 29 cm. --

Les chutes touchent un tiers des personnes âgées de 65 ans et plus et conduit à une perte de mobilité. La détection des risques facteurs de chutes est essentielle pour une intervention précoce.Six facteurs intrinsèques de chute : vision, système vestibulaire, amplitude articulaire, force musculaire, proprioception articulaire et plantaire ont été évalué par des tests cliniques avant et après une dégradation temporaire. L’équilibre a été évalué sur une plateforme de force pour le calcul de 198 paramètres.Les paramètres ont été utilisés comme variables pour la construction de modèle de réseaux de neurones et de régression logistique avec pour objectif de diagnostiquer les détériorations des facteurs testés. Les paramètres pertinents ont été sélectionnés pour être inclus aux modèles. Des modèles comprenant entre 3 et 10 conditions ont été développé, néanmoins seuls les modèles de 5 conditions et moins se sont révélés efficaces. La précision a réussi à atteindre 92% pour le modèle incluant l’amplitude de la cheville, la fatigue et la vision des contrastes.Les mesures de qualité d’équilibre ont permis de détecter des détériorations des facteurs intrinsèques testés. Cependant, ces modèles ne sont efficaces qu’avec peu de conditions. Pour construire un modèle performant avec plusieurs conditions il est nécessaire d’inclure plus de participants lors de la construction du modèle. Un outil de la sorte est intéressant pour la mise en place de programmes de prévention et de rééducation / Falls concern a third of the people aged over 65y and lead to the loss of functional ability. The detection of risks factors of falls is essential for early intervention. Six intrinsic risk factors of fall: vision, vestibular system, joint range of motion, leg muscle strength, joint proprioception and foot cutaneous proprioception were assessed with clinical tests before and after temporarily degradation. Standing balance was recorded on a force plate.From the force plate, 198 parameters of the centre of pressure displacement were computed. The parameters were used as variables to build neural network and logistic regression model for discriminating conditions. Feature selection analysis was performed to reduce the number of variables.Several models were built including 3 to 10 conditions. Models with 5 or less conditions appeared acceptable but better performance was found with models including 3 conditions. The best accuracy was 92% for a model including ankle range of motion, fatigue and vision contrast conditions. Qualities of balance parameters were able to diagnose impairments. However, the efficient models included only a few conditions. Models with more conditions could be built but would require a larger number of cases to reach high accuracy. The study showed that a neural network or a logistic model could be used for the diagnosis of balance impairments. Such a tool could seriously improve the prevention and rehabilitation practice