Thesis title: The effect of kinesthetic sensation on the postural control and balance abilities of individuals with visual impairments Objectives: Compose through the literature study appropriete balance programe for the individuals with visual impairments and measure its effect on their postural control and balance abilities. Methods: Ten visually impaired subjects, one subject with visual and vestibular impairment and one healthy subject took part in this study. Movement intervention was held once a week for eleven weeks, consisting of balance and coordination training, exercises for decreasing muscle imbalances and increasing body awareness and relaxation ability. The Footscan system was used for measuring the effect of movement intervention on the on the postural control and balance abilities of individuals with visual impairments. The testing was done before the beginning and after the finishing of all classes of movement intervention and the results of the pretest and posttest were compared with each other. Results: The movement intervention led to the improvement of postural control and balance abilities at five subjects from the total of nine subjects, who underwent pre and post testing. From the total of forty-eight carried out tests, the subjects noted improvement in twenty-two tests,...

La Dégénérescence Maculaire Liée à l’Age (DMLA) affecte actuellement plus d’un million de malades en France et concernera 288 millions de personnes dans le monde en 2040. Cette pathologie du sujet âgé est à l’origine d’un handicap fonctionnel majeur, source de perte d’autonomie et de dépendance. Malgré une forte prévalence, les performances posturales et oculomotrices des sujets atteints de DMLA restent peu étudiées et beaucoup d’interrogations sont à ce jour sans réponse. Ce projet de recherche comporte deux parties pour lesquelles nous avons utilisé différents dispositifs : les plateformes de force TechnoConcept® et Framiral®, le Mobile eyeBRAIN tracker EBT2®, et la tablette connectée Metrisquare®. Dans un premier temps, nous avons examiné l’impact de la DMLA unilatérale versus bilatérale sur le contrôle postural en comparaison avec des sujets sains âgés (Etude I), pour permettre de mettre en évidence le bénéfice de la rééducation posturale chez cette population de malades (Etudes II et III). Dans un second temps, nous avons étudié l’oculomotricité des sujets atteints de DMLA à travers leurs performances de saccades visuellement guidés et de lecture, afin de rééduquer ces mêmes performances via des exercices oculomoteurs et visuo-attentionnels (Etude IV, V et VI). En objectivant les mouvements oculaires ainsi que le déplacement du centre de pression chez les sujets atteints de DMLA uni- et bilatérale, en comparaison avec des sujets sains du même âge, nous avons cherché à confirmer notre hypothèse : le déficit visuel des sujets atteints de DMLA, à l’origine d’une malvoyance, entraine la mise en place de mécanismes adaptatifs qui, grâce à une rééducation adaptée, permettent de réduire les restrictions fonctionnelles posturales et oculomotrices. In fine, ces travaux apportent des solutions pour mieux prévenir et rééduquer ces déficits fonctionnels, grâce à des outils innovants qui permettront d’optimiser la prise en charge. / Nowadays, age-related macular degeneration (AMD) affects more than one million of people in France and will concern 288 million of people in the world in 2040. This pathology impacts elderly and generates a serious functional disability which causes autonomy loss and dependance. Despite the high prevalence, the postural and oculomotor performances of AMD subjects are little studied and there are still lot of questions without answers. This research project is composed by two parts and used different experimental techniques: TechnoConcept® and Framiral® force plateforms, Mobile eyeBRAIN tracker EBT2®, and Metrisquare® digital tablet. Firstly, we examined the impact of unilateral versus bilateral AMD in postural control, compared with healthy elderly (Study I), in order to evidence the benefits of postural training in these groups (Studies II and III). Secondly, we studied the oculomotor pattern in AMD subjects during visually guided saccades and reading tasks, to improve their performance with oculomotor and visuo-attentional exercises (Studies IV, V and VI). By objectifying eye movements as well as the displacement of center of pressure in unilateral and bilateral AMD subjects, compared with healthy age-matched controls, we want to confirm our hypothesis: the visual impairment of AMD subjects, which causes low vision, leads to the implementation of adaptive mechanisms that, through appropriate training, reduce postural and oculomotor functional restrictions.In fine, this research provides specialists with solutions to prevent and train these functional deficits with novator techniques, in order to optimize the coverage.

PURPOSE: The aims of this study were to: 1) determine the concurrent validity of the mini-Balance Evaluations Systems Test (BESTest) and the instrumented test of postural sway (iSWAY) to quantify sensory orientation impairments in adults with known postural control deficits; and 2) determine the predictive validity of iSWAY to differentiate between fallers and non-fallers in adults with known postural control deficits. The Sensory Organization Test (SOT) served as the gold standard measure. METHODS: An exploratory methodological design using secondary analysis was used. The sample consisted of 45 subjects with Parkinson¡¦s disease (PD). Subjects were concurrently tested on SOT, mini-BEST, and iSWAY. DATA ANALYSIS: Frequency distributions, central tendencies, variability, and outliers were used to analyze goodness-of-fit to the normal distribution. Mean was used for age while mode was used for fall group, fall status, and gender. The following statistical tests were used: 1) Spearman rank correlation (rs) to measure the relationship between the the mini-BEST and SOT outcome scores; 2) parametric Pearson product-moment correlation (r) was used to measure the relationship between the iSWAY and SOT outcome scores; and 3) multiple regression to analyze the association between several independent variables (iSWAY scores) and dependent variable (number falls). A receiving operator curve was constructed to determine the iSWAY score that best discriminates fallers from non-fallers. RESULTS: There was a significant and fair correlation between mini-BESTest and SOT: Composite and Total rs = 0.380 (p = 0.010); Composite and Sensory rs = 0.343 (p = 0.021), Individual Items Eyes Open, Foam Surface (EOF) and Condition five rs = 0.399 (p = 0.007). There was insignificant and little-to-no relationship between mini-BESTest and SOT Condition one. There was a moderate-to-good inverse correlation between iSWAY and SOT: Composite r = - 0.634 (p = f¬0.01); Individual items ECF and Condition five r = -0.543 (p = f¬0.01). There was significant and fair inverse correlation between iSWAY and SOT Condition one r = -0.432 (p = 0.028). There was a predictive relationship between iSWAY RANGE Composite (p = 0.040) and RMS Composite (p = 0.021) and history of falls. A multiple regression equation including three iSWAY Composite scores explained 38% variability in reported falls. The ROC curve identified an iSWAY RMS Score of less than 0.249 as demonstrating the highest likelihood of differentiating between fallers and non-fallers. DISCUSSION: Mini-BESTest and iSWAY are clinically meaningful measures of sensory orientation in persons with PD. iSWAY can help better quantify sensory orientation impairments and inform other examination findings about history of falls. Future research is needed to investigate validity of these tests with other populations and expand validation of other test components.

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With aging, the sensory, motor, and central nervous system deficiencies lead to inadequate bicycle postural control in older cyclists. Similarly, variety in riding skills leads to different bicycle postural control strategies. Cycling seems to be an automated task but keeping the bicycle stable at low speed, pedaling, and steering requires continuous physical and cognitive effort, and in long term may lead to fatigue induced by steering and stabilizing the e-bike at low forward speeds especially in older cyclists. E-bikes enables riders to cycle for langer duration and distance by reducing the physical fatigue. There is an increasing societal interest in electric bicycles where in 2021, 26. 73 billion US dollars worldwide have been invested on e-bikes and by 2027 this global market size will increase to 53.53 billion US dollars (Statista). However, with increased numbers of e-bikes, bicycle accidents due to inadequate steering and balance control by older cyclists have increased, which suggests needs for extra safety measures to maintain balance on a bicycle for challenging situation such as facing undesired disturbances or low forward speeds. We developed a prototype steering assist which aims to increase safety and improve the user experience, by reducing the steering effort and enhancing the bicycle postural control (rider-bike balance control). We investigated the potential effectiveness ofthe steering assist technology in real life challenging situations. Our present study should be considered exploratory research to find the potential effectiveness of the steering assist technology in improving the user experience and safety compared to a non-assistive e-bike. The improved bicycle postural control is validated by smaller range, variability, and rate of steering and roll trajectories when the rider is subjected to an unwanted disturbance. Improved bicycle postural control is expected based on the reduced need for compensatory behavior in the presence of assistive technology. Decreased steering effort is expected due to reduced demand for acute steering control in the anticipatory control strategy.

Le système vestibulaire joue un rôle important pour plusieurs fonctions, notamment, la perception de mouvement et le maintien de l’équilibre par l’entremise du contrôle postural. Or, une dégradation de la fonction de ce système peut avoir un impact sur le contrôle postural et ainsi augmenter le risque de chutes. Au courant des dernières années, la stimulation vestibulaire galvanique noisy (nGVS) a été démontrée comme étant efficace pour stimuler le système vestibulaire et améliorer le contrôle postural. Toutefois, les données de la nGVS sont fragmentaires et les paramètres optimaux de stimulation n’ont pas été établis. L’objectif général de la thèse était d’examiner l’effet de la nGVS sur le contrôle postural. Plus précisément, cette thèse visait à déterminer la méthodologie optimale de la nGVS et l’influence de la nGVS sur le contrôle postural d’une population présentant une dégradation de la fonction vestibulaire, soit des personnes âgées. La première étude avait pour objectif d’examiner l’effet post-stimulation de la nGVS sur le contrôle postural comparativement à une stimulation placebo. Ainsi, 14 adultes ont reçu une stimulation nGVS alors que 14 autres adultes ont reçu une stimulation placebo (sham). Le contrôle postural a été examiné avant la stimulation, immédiatement après la fin de la stimulation et 1 heure post-stimulation. Les résultats ont démontré une amélioration posturale similaire chez le groupe nGVS et le groupe sham, suggérant donc l’absence d’effet de la nGVS et ainsi un biais expérimental. De ce fait, cette étude a souligné l’importance d’un groupe contrôle lors de l’étude des effets de la nGVS sur le contrôle postural. La seconde étude visait à examiner l’effet de la densité du courant de la nGVS sur le contrôle postural en manipulant la taille des électrodes de stimulation. 36 adultes ont été séparés en 2 groupes expérimentaux, recevant la nGVS, et 1 groupe contrôle, recevant une stimulation placebo. Les groupes expérimentaux recevaient la nGVS soit avec des électrodes 35 cm2 ou 3 cm2. Ainsi, une amélioration posturale significative a été induite par la nGVS appliquée avec les électrodes de 3 cm2, soit celles avec une densité de courant plus élevée, comparativement à la nGVS avec électrodes de 35 cm2 et la stimulation placebo. La troisième étude visait à examiner l’effet de la nGVS sur le contrôle postural de personnes âgées avec et sans atteinte vestibulaire. De plus, cette étude explorait également l’effet post-stimulation de la nGVS chez les personnes âgées en comparaison à une stimulation placebo. Pour ce faire, 24 personnes âgées ont reçu la nGVS, la moitié avait une atteinte vestibulaire et l’autre moitié avait une fonction vestibulaire normale, et 12 personnes âgées ont reçu une stimulation placebo. Les données ont révélé une amélioration significative du contrôle postural induite par la nGVS comparativement à la stimulation placebo. De plus, une plus grande amélioration posturale a été observée chez les personnes âgées avec atteinte vestibulaire que les sujets âgés avec fonction vestibulaire normale après l’arrêt de la stimulation. Les résultats ont également démontré que l’amélioration posturale induite par la nGVS était maintenue après l’arrêt de la stimulation. Globalement, ces études soulignent des considérations méthodologiques de la nGVS, précisément, l’importance d’une stimulation placebo et de la densité du courant. De plus, les résultats suggèrent également un effet bénéfique de la nGVS sur le contrôle postural de personnes âgées, et celles présentant une atteinte vestibulaire en bénéficieraient davantage. Toutefois, des études futures sont requises pour déterminer les effets à long terme de la nGVS et les applications cliniques. / The vestibular system plays an important role for self-motion perception and balance through postural control. Therefore, a vestibular impairment can notably lead to a decrease of postural control and a higher risk of falls. Recently, noisy galvanic vestibular stimulation has been shown to stimulate the vestibular system and thereby improves postural control. However, until now, the optimal methodology for nGVS has not been determined, and the influence of the vestibular function on the effect of nGVS on postural has not been studied. Therefore, the main objective of the thesis was to examine the effect of nGVS on postural control. More precisely, this thesis aimed at determining the optimal methodology to apply with nGVS and to examine the effect of nGVS in a population with a decreased vestibular function, namely older adults. The first study aimed at investigating the sustained effect of nGVS on postural control compared to a sham stimulation. 28 adults were recruited and they either received nGVS or a sham stimulation. Postural control was assessed before stimulation, immediately after stimulation and 1 hour post-stimulation. Results showed a similar improvement of postural control for nGVS and sham, therefore suggesting an experimental bias. This study underlined the importance of a sham stimulation in the exploration of the sustained effect of nGVS on postural stability. The second study aimed at examining the effect of nGVS current density on postural control. To manipulate current density, two different sizes of electrodes were used, therefore 12 adults received nGVS with 35 cm2 electrodes while 12 others received nGVS with 3 cm2 electrodes. The nGVS groups were compared to 12 adults receiving a sham stimulation. The results demonstrated that only nGVS applied with 3 cm2 induced a significant improvement of postural compared to nGVS applied with 35 cm2 and sham stimulation. Therefore, it suggested that higher current density is needed to improve vestibular function. The third study aimed at determining the effect of nGVS on postural control in older adults with and without vestibular impairment. Furthermore, a second objective was to examine the post-stimulation effect of nGVS in older adults compared to a sham stimulation. 36 older adults were recruited, and 24 received nGVS while 12 received a sham stimulation. The nGVS group was composed of 12 older adults with vestibular impairment and 12 with a normal vestibular function. The results revealed that nGVS significantly improved postural control of older adults compared to a sham stimulation. The improvement induced by nGVS was significantly greater in older adults with vestibular impairment compared to older adults with normal vestibular function after the end of stimulation. Furthermore, the effect of nGVS on postural control was sustained after the end of the stimulation period. In summary, these studies underlined important methodological parameters of nGVS and results showed that nGVS could be a promising approach to use with populations with a decreased vestibular function, such as older adults. However, further studies are needed to examine the extent of the sustained effect of nGVS on postural control and to evaluate clinical applications.

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