The physiological energy requirements of prosthetic gait in lower-limb amputees have been observed to be significantly greater than those for able-bodied subjects. However, existing models of energy flow in walking have not been very successful in explaining the reasons for this additional energy cost. Existing mechanical models fail to capture all of the components of energy cost involved in human walking. In this thesis, a new model is developed that estimates the physiological cost of walking for an able-bodied individual; the same cost of walking is then computed using a variation of the model that represents a bi-lateral below-knee amputee. The results indicate a higher physiological cost for the amputee model, suggesting that the model more accurately represents the relative metabolic costs of able-bodied and amputee walking gait. The model is based on a two-dimensional multi-body mechanical model that computes the joint torques required for a specified pattern of joint kinematics. In contrast to other models, the mechanical model includes a balance controller component that dynamically maintains the stability of the model during the walking simulation. This allows for analysis of many consecutive steps, and includes in the metabolic cost estimation the energy required to maintain balance. A muscle stress based calculation is used to determine the optimal muscle force distribution required to achieve the joint torques computed by the mechanical model. This calculation is also used as a measure of the metabolic energy cost of the walking simulation. Finally, an optimization algorithm is applied to the joint kinematic patterns to find the optimal walking motion for the model. This approach allows the simulation to find the most energy efficient gait for the model, mimicking the natural human tendency to walk with the most efficient stride length and speed.

The purpose of this thesis was to examine the capacity for acquisition and retention of practice-related improvements in compensatory posture control and the nature of postural motor learning among healthy young and older adults repeatedly exposed to continuous surface motion via a translating platform. Although much research has been conducted to examine the strategies adopted by the central nervous system to control posture in response to external perturbations, the learning capabilities of this system have remained relatively unexplored. Many of the studies that have explored practice-related changes in balance performance have focused on short-term adaptations to highly predictable stimuli. Borrowing from implicit sequence learning paradigms, we developed two experimental protocols to examine postural motor learning for a compensatory balance task in an environment with limited predictability. Applying key principles of motor learning to our experimental design including retention intervals and a transfer task enabled us to draw conclusions about the permanency and specificity of the observed changes. Our investigations revealed practice-related changes in the motor organization of posture control. In young adults, a shift in the complexity of the control strategy occurred which lead to improvements in spatial and temporal control of the COM. In contrast, a majority of older adults persisted with a simplified control strategy which restricted improvements in COM control. Importantly, despite control strategy differences, the two groups showed comparable rates of improvement in almost all outcome measures including measures of trunk stability and temporal COM control. Longer-term retention of behavioural changes provided evidence for learning in young adults. Similar maintenance of improvements was observed for some outcome measures in older adults. Where significant losses in performance occurred in this group, retention was evident in the rapid reacquisition of performance to the level of proficiency achieved in original practice. Based on these results, we concluded that age affected the adapted control strategy but not the capacity for postural motor learning. Further, regardless of age or protocol, the pattern of postural perturbations did not influence acquisition of a strategy of stability and thus, we concluded that postural motor learning under the current conditions was non-specific, that is, it did not involve sequence-specific learning. These results provide important insight into the generalized nature of compensatory postural motor learning and subsequently, into the potential for positive transfer of balance skill to other balance tasks.

The physiological energy requirements of prosthetic gait in lower-limb amputees have been observed to be significantly greater than those for able-bodied subjects. However, existing models of energy flow in walking have not been very successful in explaining the reasons for this additional energy cost. Existing mechanical models fail to capture all of the components of energy cost involved in human walking. In this thesis, a new model is developed that estimates the physiological cost of walking for an able-bodied individual; the same cost of walking is then computed using a variation of the model that represents a bi-lateral below-knee amputee. The results indicate a higher physiological cost for the amputee model, suggesting that the model more accurately represents the relative metabolic costs of able-bodied and amputee walking gait. The model is based on a two-dimensional multi-body mechanical model that computes the joint torques required for a specified pattern of joint kinematics. In contrast to other models, the mechanical model includes a balance controller component that dynamically maintains the stability of the model during the walking simulation. This allows for analysis of many consecutive steps, and includes in the metabolic cost estimation the energy required to maintain balance. A muscle stress based calculation is used to determine the optimal muscle force distribution required to achieve the joint torques computed by the mechanical model. This calculation is also used as a measure of the metabolic energy cost of the walking simulation. Finally, an optimization algorithm is applied to the joint kinematic patterns to find the optimal walking motion for the model. This approach allows the simulation to find the most energy efficient gait for the model, mimicking the natural human tendency to walk with the most efficient stride length and speed.

The purpose of this thesis was to examine the capacity for acquisition and retention of practice-related improvements in compensatory posture control and the nature of postural motor learning among healthy young and older adults repeatedly exposed to continuous surface motion via a translating platform. Although much research has been conducted to examine the strategies adopted by the central nervous system to control posture in response to external perturbations, the learning capabilities of this system have remained relatively unexplored. Many of the studies that have explored practice-related changes in balance performance have focused on short-term adaptations to highly predictable stimuli. Borrowing from implicit sequence learning paradigms, we developed two experimental protocols to examine postural motor learning for a compensatory balance task in an environment with limited predictability. Applying key principles of motor learning to our experimental design including retention intervals and a transfer task enabled us to draw conclusions about the permanency and specificity of the observed changes. Our investigations revealed practice-related changes in the motor organization of posture control. In young adults, a shift in the complexity of the control strategy occurred which lead to improvements in spatial and temporal control of the COM. In contrast, a majority of older adults persisted with a simplified control strategy which restricted improvements in COM control. Importantly, despite control strategy differences, the two groups showed comparable rates of improvement in almost all outcome measures including measures of trunk stability and temporal COM control. Longer-term retention of behavioural changes provided evidence for learning in young adults. Similar maintenance of improvements was observed for some outcome measures in older adults. Where significant losses in performance occurred in this group, retention was evident in the rapid reacquisition of performance to the level of proficiency achieved in original practice. Based on these results, we concluded that age affected the adapted control strategy but not the capacity for postural motor learning. Further, regardless of age or protocol, the pattern of postural perturbations did not influence acquisition of a strategy of stability and thus, we concluded that postural motor learning under the current conditions was non-specific, that is, it did not involve sequence-specific learning. These results provide important insight into the generalized nature of compensatory postural motor learning and subsequently, into the potential for positive transfer of balance skill to other balance tasks.

Fall-related injuries in adults over the age of 65 pose an important public health issue especially with an increasing number of older adults living in retirement homes and nursing homes. Safety floors have been developed as an intervention to reduce the risk of these injuries. However, their effects on balance control reactions had never been tested during certain activities of daily living in retirement home dwellers. This research investigated how balance reactions are affected by the mechanical properties of safety flooring in older adults. The safety flooring showed minimal impact on the balance reactions while retaining force attenuation properties. There were two studies as part of this thesis. The purpose of the first study was to determine whether the Nintendo Wii Balance Board (WBB) can be used as an appropriate substitution for a force plate when measuring balance reactions during common tests used to assess balance in older adults. Specifically, I characterized the technical specifications of the WBB and compared them to those of the force plate, showing that the two devices yielded similar responses during balance measures of quiet stance. The second study investigated the effect of two traditional floors and three safety flooring systems on balance control mechanisms (based on changes in underfoot centre of pressure) during sit-to-stand and quiet stance tasks in retirement home-dwellers. The results of this study provided evidence supporting the potential for safety floors to reduce fall-related injury risk without impairing balance and mobility of users. Additional research may want to assess WBB performance during dynamic tasks involving shear forces. The results from this study supports prospective clinical investigations of pilot installations of safety flooring in retirement and nursing home settings to evaluate their real life effects on fall related injuries.

Fall-related injuries in adults over the age of 65 pose an important public health issue especially with an increasing number of older adults living in retirement homes and nursing homes. Safety floors have been developed as an intervention to reduce the risk of these injuries. However, their effects on balance control reactions had never been tested during certain activities of daily living in retirement home dwellers. This research investigated how balance reactions are affected by the mechanical properties of safety flooring in older adults. The safety flooring showed minimal impact on the balance reactions while retaining force attenuation properties. There were two studies as part of this thesis. The purpose of the first study was to determine whether the Nintendo Wii Balance Board (WBB) can be used as an appropriate substitution for a force plate when measuring balance reactions during common tests used to assess balance in older adults. Specifically, I characterized the technical specifications of the WBB and compared them to those of the force plate, showing that the two devices yielded similar responses during balance measures of quiet stance. The second study investigated the effect of two traditional floors and three safety flooring systems on balance control mechanisms (based on changes in underfoot centre of pressure) during sit-to-stand and quiet stance tasks in retirement home-dwellers. The results of this study provided evidence supporting the potential for safety floors to reduce fall-related injury risk without impairing balance and mobility of users. Additional research may want to assess WBB performance during dynamic tasks involving shear forces. The results from this study supports prospective clinical investigations of pilot installations of safety flooring in retirement and nursing home settings to evaluate their real life effects on fall related injuries.

abstract: The increased risk of falling and the worse ability to perform other daily physical activities in the elderly cause concern about monitoring and correcting basic everyday movement. In this thesis, a Kinect-based system was designed to assess one of the most important factors in balance control of human body when doing Sit-to-Stand (STS) movement: the postural symmetry in mediolateral direction. A symmetry score, calculated by the data obtained from a Kinect RGB-D camera, was proposed to reflect the mediolateral postural symmetry degree and was used to drive a real-time audio feedback designed in MAX/MSP to help users adjust themselves to perform their movement in a more symmetrical way during STS. The symmetry score was verified by calculating the Spearman correlation coefficient with the data obtained from Inertial Measurement Unit (IMU) sensor and got an average value at 0.732. Five healthy adults, four males and one female, with normal balance abilities and with no musculoskeletal disorders, were selected to participate in the experiment and the results showed that the low-cost Kinect-based system has the potential to train users to perform a more symmetrical movement in mediolateral direction during STS movement. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2016

Contexte et objectif – Les patients âgés gonarthrosiques présentent une dégradation du contrôle postural. Les méthodes non pharmacologiques sont aujourdhui recommandées comme option de première intention dans la gestion de l’arthrose. L’hydrothérapie fait partie des moyens de rééducation à disposition des patients âgés atteints d’arthrose du genou pour ses effets antalgiques et musculaires. Cependant, peu d’études sont actuellement disponibles concernant l’effet de l’hydrothérapie sur le contrôle postural, associée ou non à des programmes de rééducation individuels ciblés. Par ailleurs, le contrôle postural est susceptible de variations diurnes. Cette étude a eu pour objet de décrire le contrôle postural des personnes gonarthrosiques à quatre périodes de la journée, puis de comparer l’amélioration du contrôle postural au cours de deux programmes de rééducation différents recourant à l’hydrothérapie. Matériel et méthodes - Deux-cent-quatre-vingt quatre patients souffrant d’arthrose du genou ont été inclus dans cette étude. Le bilan posturographique a été réalisé une semaine avant la cure thermale en condition simple (yeux ouverts, support stable) et en conditions sensorielles contradictoires (vision faussée ou indisponible, proprioception perturbée). Pour évaluer les variations diurnes de la stabilité posturale, les patients ont été randomisés à quatre périodes d’essai dans la journée définies comme suit : 8h-10h, 10h-12h, 13h-15h, 15h-17h. L’influence du sexe, de l’âge, de la taille, du poids et de l’indice de masse corporelle sur la stabilité posturale a été évaluée. La gonalgie a également été évaluée à quatre périodes d’essai. Par la suite, les patients ont été randomisés en deux groupes de rééducation différents pour recevoir des traitements aquatiques : groupe cure classique (hydrothérapie efficace prouvée, c’est-à-dire groupe témoin) et groupe cure active (hydrothérapie combinant des programmes de réhabilitation individuels ciblés). Les bilans de posturographie statique ont été réalisés respectivement à 21 jours, 42 jours et 90 jours après le début de l’hydrothérapie. Résultats –Les tests posturographiques ont été réalisés chez 241 patients (âge moyen : 64,8 + 8,7 ans ; 82 hommes). Le contrôle de l’équilibre était plus efficace l’après-midi que le matin à la fois dans les conditions simple (p = 0,012) et sensorielle contradictoire (p = 0,047), en particulier en début d’après-midi lorsque la vision et la proprioception étaient disponibles (p = 0,026) ou perturbées (p = 0,019). La gonalgie a été plus prononcée le matin que l’après-midi (p < 0,001). La variation diurne du contrôle postural était plus marquée chez les patients plus âgés, de poids plus élevé, de sexe masculin, dans les conditions d’essais différentes (p < 0,05). Les deux cures d’hydrothérapie ont eu des effets curatifs considérables sur la restauration du contrôle de l’équilibre. Une meilleure précision des oscillations posturales a été constatée dans le groupe cure active par rapport au groupe cure classique, 42 jours après le début de l’hydrothérapie (p = 0,020), en particulier lorsque la proprioception a été perturbée avec (p = 0,028) ou sans (p = 0,025) vision disponible. Dans les deux groupes a été observée une stabilité posturale comparable dans un délai de trois mois. Conclusions - Cette étude a montré une meilleure stabilité posturale chez les patients atteints d’arthrose du genou, en début d’après-midi par rapport à la fin de matinée dans les situations sensorielles simples ou contradictoires. Il a été constaté que ces variations étaient également liées à l’âge, au sexe, au poids et pourraient être expliquées par la douleur articulaire fluctuante dans la journée. Considérée comme un traitement non pharmacologique applicable et recommandé, l’hydrothérapie est bénéfique à l’amélioration de la stabilité posturale chez les patients âgés atteints d’arthrose du genou, en particulier combinant un programme de réhabilitation individuel ciblé. [...] / Background and Objective – Increasing evidence supports balance control impairment in elderly patients with knee osteoarthritis (OA). Current guidelines recommend non-pharmacologic methods as first-line options in the management of OA. Hydrotherapy is a beneficial training medium for rehabilitation in elderly knee OA patients. However, few indications at present are available concerning the effect of hydrotherapy combining with targeted individual rehabilitation programs to improve balance control. Meanwhile, there is limited data on diurnal variation of balance control in these patients. This study aimed to investigate postural stability in elderly patients with symptomatic knee OA during different periods in a daytime before the spa therapy, then to study the results obtained before and after hydrotherapy to compare the improvement of balance control in these patients in two different water-based rehabilitation programs. Materials and Methods – Two-hundred and eighty-four knee OA patients were enrolled in this study. Static posturography using a vertical force platform was performed one week before spa therapy in simple (eyes open, firm support) and conflicting sensory (vision altered or unavailable, proprioception altered) conditions. To assess diurnal postural variations, patients were randomized to four testing sessions in a daytime defined as follows: 8-10am, 10-12am, 1pm-3pm, 3pm-5pm. Influence of sex, age, height, weight, and body mass index on postural stability was evaluated. Knee pain was also assessed in four testing sessions. Patients were then randomized to two different rehabilitated groups to receive spa therapies. Classic treatment group as a control received the efficacy proven spa water therapy, and active treatment group received spa water therapy combining with targeted individual rehabilitation programs. Static posturographies were carried out respectively in 21 days, 42 days and 90 days after the beginning of hydrotherapy. Results – Posturographic tests were completed for 241 patients (mean age: 64.8 + 8.7 years; 82 males). Balance control was more efficient in the afternoon than in the morning both in simple (p = 0.012) and conflicting sensory conditions (p = 0.047), especially in early afternoon when vision and proprioception were available (p = 0.026) or disturbed (p = 0.019). Patients’ knee pain was more pronounced in the morning than in the afternoon (p < 0.001). Diurnal variation of balance control was more noticeable in older, heavier, and male patients under different testing conditions (p < 0.05). Both the water-based therapies had considerable curative effect on balance control restoration. Better postural sway precision were found in active group than classic group 42 days after the beginning of hydrotherapy (p = .020), especially when proprioception was interfered with (p = .028) or without (p = .025) an available vision. Both of the groups have been observed a comparable postural stability in a three-month term. Conclusions – This study showed that better postural stability was observed in patients with knee OA in early afternoon than in late morning in simple and conflicting sensory situations. These variations appeared also to be related to age, sex, and weight and could be explained by fluctuant joint pain in a daytime. As feasible and recommended non-pharmacologic treatment, hydrotherapy is beneficial to the improvement of postural stability in elderly patients with knee OA, especially combining with targeted individual rehabilitation programs. These findings are important for future studies aiming at enhancing postural stability in knee OA patients and should be taken into account in the management of knee OA to generate applicative approaches to prevent the occurrence of adverse events in patient’s daily life.

Depuis quelques années, de nouveaux systèmes de rééducation à la marche de type orthèse tels que le Lokomat® (Hocoma AG, Volketswil, Suisse) apparaissent dans les laboratoires de recherche clinique. Ces outils sont proposés, via des programmes de réentraînement à l’effort, pour la rééducation des patients présentant des altérations de l’appareil locomoteur. Leur but principal consiste à réacquérir une marche fonctionnelle grâce à une simulation des différentes phases de la marche et à une stimulation sensitive nourrissant les réafférences proprioceptives. Le Lokomat® permet donc, par une répétition prolongée des patrons de marche, un apprentissage sensori-moteur actif et progressif pour le patient. Les objectifs de notre étude sont : (1) de caractériser les processus de contrôle de l’équilibre (coordinations multi-segmentaires) pendant la marche chez des enfants atteints de paralysie cérébrale, comparativement à un groupe d’enfants à développement typique, en analysant les différentes stratégies mises en œuvre pour se propulser vers l’avant tout en préservant leur équilibre, puis (2) de mettre en évidence l’apport d’une rééducation robotisée à la marche dans l’amélioration et/ou la modification des paramètres biomécaniques de la marche chez des enfants atteints de paralysie cérébrale et d’en observer les influences éventuelles sur la motricité globale de l’enfant (nouvelles stratégies, amélioration du rapport coût/bénéfice, etc.). / In recent years, robotically driven orthoses such as the Lokomat® (Hocoma AG, Volketswil, Switzerland) appear in clinical research laboratories. These tools are proposed through gait training programs for the rehabilitation of patients with locomotor disorders. Their main purpose consists to reacquire functional gait through a simulation of the different phases of gait and a sensory stimulation feeding proprioceptive feedback. The Lokomat® allows by an extended repetition of gait patterns an active and progressive sensorimotor learning for the patient. The aims of our study are: (1) to characterize balance control processes (multisegmental coordination) in gait children with cerebral palsy compared to a group of typical development children by analyzing the different strategies involved to maintain forward motion while maintaining dynamic balance, then (2) to show the effects of robot-assisted rehabilitation in gait retraining and show this impacts upon the postural control of children with cerebral palsy (news strategies, ratio cost/benefit improvement, etc).

The overall goal of my research was to advance our understanding of the potential for novel compliant flooring systems to reduce the risk for fall-related injuries in older adults, including fall-related traumatic brain injury (TBI). This entailed an assessment of how these floors affect the competing demands of fall-related TBI – impact severity attenuation in concert with minimal concomitant impairments to balance control and postural stability. Two studies are included as part of this thesis. The first study used a mechanical drop tower to assess the effects of four traditional flooring systems and six novel compliant flooring conditions on the impact dynamics of a surrogate headform during the impact phase of simulated ‘worst- case’ head impacts. The second study entailed an assessment of the effect of two traditional and three novel compliant floors on the initial phase of the compensatory balance reactions of older adult men and women living in a residential-care facility environment following an externally induced perturbation using a tether-release paradigm. Overall, this thesis demonstrates that novel compliant floors substantially attenuate the forces and accelerations applied to the head during simulated worst- case impacts when compared to traditional flooring surfaces such as vinyl and carpet with underpadding. These benefits are achieved without compromising indices of balance control, supported by the finding that parameters characterizing early compensatory balance reactions were unaffected by the novel compliant floors tested. This work supports the introduction of pilot installations of novel compliant flooring systems into environments with high incidences of falls to test their effectiveness at reducing fall-related injuries in clinical settings.