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Certains besoins de santé spécifiques ont contribué au développement du travail présenté ici, en particulier dans le domaine de la kinésithérapie dans lequel l’étude de l’équilibre postural est étudiée. Les solutions qui existent aujourd'hui sur le marché sont coûteuses, disponibles uniquement dans les grands hôpitaux ou dans des salles dédiées, avec un faible taux de fréquentation de la population, principalement dans des endroits plus éloignés des grands centres urbains. Ce travail a été développé en collaboration avec une équipe constituée de kinésithérapeutes, de chercheurs en génie électrique et en génie mécanique du laboratoire G-SCOP, Grenoble INP, Institut d’Ingénierie, Univ. Grenoble Alpes, France. Cette équipe cherche des solutions à faible coût qui répondent aux besoins de la société en général, en mettant l'accent sur la santé, mais également sur la vulgarisation scientifique, en diffusant ses travaux lors de manifestations de type fête de la Sciences dans la région et pour la communauté. Les travaux ont débuté avec une plateforme de force développée en 2016, conjointement par des chercheurs de l'UNESP (une Université de l'état Sao Paulo au Brésil) et du laboratoire G-SCOP. A cette solution a été ajoutée une nouvelle interface électronique, développée dans le but de fournir des informations sur le déplacement du centre de pression du patient. Un mécanisme a également été mis en place pour assurer la synchronisation entre les informations capturées par les capteurs installés sur la plate-forme et un capteur Microsoft Kinect. De nouveaux outils logiciels ont été proposés pour capturer et analyser les résultats. Le traitement des données permet de créer un modèle tridimensionnel détaillé contenant la cinématique de plusieurs articulations du corps humain et leur comportement respectif en fonction du temps. La mise en œuvre du capteur Kinect synchronisé avec la plate-forme de force permet de comparer le Centre de Pression avec le Centre de masse en vue de proposer un outil plus léger et moins cher à la communauté des praticiens hospitaliers. / Some specific health needs contributed to the development of the work presented here, especially in Physical Therapy in which the Postural Equilibrium is studied. The solutions that exist today in the market are of expensive, available only in large hospitals or in dedicated rooms, with low index of attendance to the population, mainly in places more distant of the great urban centers. This work was developed in cooperation with a team constituted of Phisiotherpists, Electrical Engineering and Mechanical Engineering from of the G-SCOP Laboratory, Grenoble INP, Institute of Engineering Univ. Grenoble Alpes, France. This team seeks low cost solutions that meet the needs of society in general, with a focus on health, but also with a focus on the popularization of science, disseminating its work in basic schools in the region and also in the community. The work began with a strength platform developed in 2016, jointly by researchers from UNESP, Sao Paulo, Brasil, and the G-SCOP Laboratory. To this solution was added a new electronic interface, developed with the purpose of providing information on the displacement of the patient pressure center. A mechanism was also implemented to ensure synchronization between information captured by sensors installed on the platform and a Microsoft Kinect sensor. New software tools were developed to capture and analyze the results. The data treatment allows the creation of a detailed three-dimensional model, containing the kinematics of several joints of the human body and their respective positional behavior, as a function of time. With the implementation of the Kinect sensor, synchronised with the force platform, it is also possible to evaluate the kinematic and positional biomechanical parameters.

Human upright posture exhibits an everlasting oscillatory behavior of complex nature, called as human postural sway. Variations in the position of the Center-of-Pressure (CoP) were used to describe the human postural sway. In this study / CoP data, which has experimentally been collected from 28 different subjects (14 males and 14 females with their ages ranging from 6 to 84), who were divided into 4 groups according to their ages has been analyzed. The data collection from each of the subjects was performed in 5 successive trials, each of which has lasted for 180-seconds long. Linear analysis methods such as the variance/standard deviation, Fast Fouri&eacute / r Transformation, and Power Spectral Density estimates were applied to the detrended CoP signal of human postural sway. Also the Run test and Ensemble averages methods were used to search for stationarity and ergodicity of the CoP signal respectively. Furthermore, in order to reveal the nonlinear characteristics of the human postural sway, its dynamics were reconstructed in m-dimensional state space from the CoPx signals. Then, the correlation dimension (D2) estimates from the embedded dynamics were calculated. Additionally, the statistical and dynamical measures computed were checked against any significant changes, which may occur during aging. The results of the study suggested that human postural sway is a stationary process when 180-second long biped quiet stance data is considered. In addition, it exhibits variable dynamical structure complex in nature (112 deterministic chaos versus 28 stochastic time series of human postural sway) for five successive trials of 28 different subjects. Moreover, we found that groups were significantly different in the correlation dimension (D2) measure (p&amp / #8804 / 0.0003). Finally, the behavior of the experimental CoPx signals was checked against two types of linear processes by using surrogate data method. The shuffled CoPx signals (Surrogate I) suggested that temporal order of CoPx is important / however, phase-randomization (Surrogate II) did not change the behavioral characteristics of the CoPx signal.

Orientador: Prof. Dr. Marcos Duarte / Dissertação (mestrado) - Universidade Federal do ABC. Programa de Pós-Graduação em Engenharia Biomédica, 2016. / Alterações associadas ao envelhecimento e algumas doenças podem afetar o controle postural influenciando de maneira negativa a qualidade de vida das pessoas. Há muitos testes que podem ser utilizados para descrever o controle postural do ser humano, entretanto, ainda não há um consenso de quais são os melhores testes a serem empregados durante a avaliação para extrair informações relevantes da condição de equilíbrio do indivíduo. O objetivo deste estudo foi implementar um conjunto de dados público com resultados de avaliações qualitativas e quantitativas relacionadas ao equilíbrio do corpo humano e assim permitir que diferentes centros de pesquisa tenham acesso a dados de referência para comparação e análises em um mesmo conjunto de dados. O controle postural dos sujeitos foi avaliado pela técnica de posturografia utilizando uma plataforma de força e pelo Mini Balance Evaluation Systems Tests. No teste de posturografia, nós avaliamos os sujeitos durante a postura ereta quieta por 60 s em quatro diferentes condições posturais em que a informação visual e de superfície de apoio foram manipuladas: em superfície firme com olhos abertos, em superfície firme com olhos fechados, em superfície macia com olhos abertos, e em superfície macia com olhos fechados. Cada condição postural foi desempenhada três vezes por cada sujeitos e a ordem das condições posturais foi randomizada entre os sujeitos. Em adição, para melhor caracterizar os sujeitos nós empregamos os seguintes testes: Short Falls Efficacy Scale International, Questionário Internacional de Atividade Física ¿ versão curta, e Trail Making Test. Os sujeitos também foram entrevistados para coletar informações referentes às suas características socioculturais, demográficas e de saúde. O conjunto de dados compreende sinais da plataforma de força (dados brutos das forças, dos momentos de força, e dos centros de pressão) de 163 sujeitos e informações sobre os sujeitos, as condições de equilíbrio, e os resultados das demais avaliações. Este estudo está publicado em Santos DA, Duarte M. (2016) A public data set of human balance evaluations. PeerJ Preprints 4:e2162v1 https://doi.org/10.7287/peerj.preprints.2162v1. / Age-related disabilities and certain illnesses affect body balance in humans and can negatively influence their health and quality of life. There is a large variety of tests to describe balance in humans and there is no consensus yet on the best tests and their implementation details in order to extract meaningful information about subject¿s balance condition. The goal of this study was to create a public data set with results of qualitative and quantitative evaluations related to human balance to allow access of a normative reference for data comparison and testing analysis from different centers. Subject¿s balance was evaluated by posturography using a force platform and by the Mini Balance Evaluation Systems Tests. In the posturography test, we evaluated subjects during standing still for 60 s in four different conditions where vision and the standing surface were manipulated: on a rigid surface with eyes open; on a rigid surface with eyes closed; on an unstable surface with eyes open; on an unstable surface with eyes closed. Each condition was performed three times and the order of the conditions was randomized among subjects. In addition, the following tests were employed in order to better characterize each subject: Short Falls Efficacy Scale International; International Physical Activity Questionnaire Short Version; and Trail Making Test. The subjects were also interviewed to collect information about their socio-cultural, demographic, and health characteristics. The data set comprises signals from the force platform (raw data for the force, moments of forces, and centers of pressure) of 163 subjects and information about the subjects and balance conditions and the results of the other evaluations. The results of this study are also published in Santos DA, Duarte M. (2016) A public data set of human balance evaluations. PeerJ Preprints 4:e2162v1 https://doi.org/10.7287/peerj.preprints.2162v1.

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As falls and fall-related injuries are a major cause of injuries, the purpose of this study was to investigate whether, and to what extent, the stage combat fall technique training could reduce the impact forces of falls from standing. Twenty-six healthy young adults (14 males and 12 females) participated in our study, and were randomly assigned to either a training group or non-training (control) group. Both groups completed a pre-intervention and a post-intervention fall testing session, separated by two weeks, in which they performed naturalistic falls. The training group performed identical pre-intervention fall testing as the control group, and was then required to receive four 1-hour training sessions in the course of two weeks, led by a certified stage combat fall technique training instructor. The training group then completed a post-intervention fall testing session where they performed naturalistic falls and also falls using the fall technique they learned. Falls were induced in both forward and backward directions using a tether-release protocol. Differences between control and training groups at pre-training, and group differences in the change in dependent measures with training, were examined using Mann-Whitney U tests. The results showed that, following stage-combat fall training, the training group exhibited 32% and 35% reduction in median impact forces for forward and backward falls respectively, while the control group exhibited 5% and 2% reductions (p = 0.002 and <0.001). In addition, the training group showed shorter backward fall duration as well as longer impact time, larger impulse, and longer or larger center-of-pressure based measures for both directions of falling than the control group. However, training was not associated with reduced impact force during the naturalistic falls of the training group. To our knowledge, this was the first study to investigate the stage combat fall technique training and demonstrate its effectiveness as an intervention to reduce impact forces of falls, thereby exploring the potential to reduce the number of fall-related injuries. While these falls were induced from standing, whether these results would transfer to an unanticipated fall while walking due to a slip/trip remain to be explored. / Master of Science / As falls and fall-related injuries are a major cause of injuries, the purpose of this study was to investigate whether, and to what extent, the stage combat fall technique training could reduce the impact forces of falls from standing. Twenty-six healthy young adults (14 males and 12 females) participated in our study, and were randomly assigned to either a training group or non-training (control) group. Both groups completed a pre-intervention and a post-intervention fall testing session, separated by two weeks, in which they performed naturalistic falls. The training group was required to receive four 1-hour training sessions in the two-week intervention period, led by a certified stage combat fall technique training instructor. The training group then completed a post-intervention fall testing session where they performed naturalistic falls and also falls using the fall technique they learned. The results showed that, following stage-combat fall training, the training group exhibited nearly a 1/3rd reduction in impact forces for both forward and backward falls, while the control group only exhibited 5% and 2% reductions respectively. Our analysis also showed that the training group achieved this reduction in impact force by increasing the impact time and spreading out their bodies more, to distribute the impact over a larger area. To our knowledge, this was the first study to investigate the stage combat fall technique training and demonstrate its effectiveness as an intervention to reduce impact forces of falls, thereby exploring the potential to reduce the number of fall-related injuries.

The central integration of sensory information provided by various afferent receptors is required to control human movement. Although the function of individual afferent receptors is known, the complexity and interactivity of afferent information remains unclear, especially in scenarios which involve the reduction of information provided by one or more afferent receptors. Reduced plantar sensitivity is commonly associated with postural instability, which occurs in ageing, peripheral neuropathies, and other neurological disorders like Parkinson's disease. Although there has been a great advance in understanding afferent inputs during recent years, the role of afferent information in controlling movement is still unclear. Therefore, the aim of the present thesis is to investigate the effects of reduced plantar sensitivity on quasi-static and dynamic balance control, as well as muscle reflexes. The current thesis is comprised of five experiments. Two experiments were designed as preliminary investigations, while the remaining three experiments addressed the main questions of this thesis. The first experiment investigated a basic question about subjective foot sensitivity (vibration perception) measured in two different body positions: standing and sitting. Results of Experiment I showed no differences of vibration perception between both measured conditions. Therefore, comparing data from plantar sensitivity vibration tests performed during sitting and during standing (e.g. balance) is feasible. In Experiment II, the role of afferent information from plantar mechanoreceptors on quasi-static balance was investigated using two different cooling procedures: a permanently cooling thermal platform and conventional ice pads. COP total excursions, plantar temperatures, and scores of a Visual Analogue Scale (VAS) regarding subjective pain were analyzed. Experiment II demonstrated that constant and controllable cooling via the thermal platform is the superior approach with respect to subjective pain (VAS) and to reach and maintain the desired temperature throughout the trials. Furthermore, only cooling via the thermal platform induced postural instability, revealed by increased COP values. This instability was expected due to reduced plantar input, indicating no compensation by other sensory systems. Experiment III focused on the inter- and intraday- reliability of dynamic balance responses using the Posturomed device. Generally good relative and absolute reliability were found for COP excursions. This outcome was fundamental to proceed with dynamic balance measurements using the same setup. Subsequently, effects of reduced plantar cutaneous inputs via cooling on anticipatory and compensatory balance responses (unexpected perturbations) were explored in Experiment IV. COP and EMG data were used to analyze anticipatory and compensatory balance responses. No differences in COP or EMG parameters were found for the anticipatory responses after hyper-thermia, while decreased values for compensatory balance responses were observed in response to cooling. This was interpreted as a kind of overcompensatory behavior of the central nervous system (CNS) due to more cautious behavior induced after plantar cooling. Finally, the question regarding the interaction between afferent receptors arose in Experiment V, in which the effects of reduced plantar temperatures on the Achilles tendon stretch reflex and plantar flexion were examined. Short latency responses and maximal force of plantar flexion were analyzed. Cooling resulted in decreased amplitudes of short latencies, as well as in delays in time to maximal force of plantar flexion. These findings suggest that plantar inputs participate complementarily in the Achilles stretch reflex. Collectively, the current thesis contributes to understanding how plantar receptors are involved in movement control; not only do they seem to work as independent contributors, but they also appear to interact with other afferent receptors. Furthermore, an important outcome is that the reduced plantar inputs seem to induce different alterations in the organization of CNS inputs and outputs, according to different balance tasks: quasi-static responses, anticipatory responses, and compensatory responses. For the future, the use of other methods like microneurography and electroencephalography could be helpful to gain even more understanding of afferent interactions during the control of movements. Similar protocols may also be implemented in other populations, such as elderly people or patients suffering from neurological disorders, who exhibit continued decline or degeneration of sensory receptors. / Die zentrale Integration von sensorischen Informationen, die aus verschiedenen afferenten Rezeptoren zur Verfügung gestellt werden, ist erforderlich, um die menschliche Bewegung zu steuern. Obwohl die Funktion der einzelnen afferenten Rezeptoren bekannt ist, bleibt die Komplexität und Interaktivität von afferenten Information unklar, insbesondere in Szenarien, in denen die Verminderung von Informationen aus einem oder mehreren afferenten Rezeptoren eintritt. Reduzierte plantare Sensibilität wird häufig im Zusammenhang mit Haltungsinstabilität verbunden. Dies tritt häufig während des Alterns ein, bei peripheren Neuropathien und anderen neurologischen Erkrankungen, wie etwa bei der Parkinson-Krankheit. Obwohl es in den vergangen Jahren große Entwicklungen was das Verständnis afferenter Inputs gab, ist die Rolle afferenter Information bei der Bewegungskontrolle immer noch unklar. Daher ist das Ziel der vorliegenden Dissertation, den Einfluss der Beeinträchtigung der plantaren Sensibilität auf das quasi-statische und dynamische Gleichgewicht, sowie auf den Reflex der Achillessehne, zu untersuchen. Die vorliegende Dissertation ist dazu aus fünf Untersuchungen aufgebaut. Zwei Untersuchungen werden als Voruntersuchungen präsentiert, während die übrigen drei Untersuchungen auf die Kernfragen dieser Doktorarbeit gerichtet sind. Die erste Untersuchung beschäftigt sich mit der grundlegenden Fragestellung bzgl. der subjektiven Fußsensibilität (Vibrationswahrnehmung), die in zwei verschiedenen Körperpositionen gemessen wurde: Im Stehen und im Sitzen. Ergebnisse aus Untersuchung I zeigten keine Unterschiede der Vibrationswahrnehmung zwischen den beiden Körperpositionen. Daher ist es möglich, Vergleiche zwischen Daten aus plantaren Vibrationswahrnehmungstests während des Sitzens und des Stehens (z.B. bei Gleichgewichtstests) durchzuführen. In Untersuchung II wurde die Rolle afferenter Informationen plantarer Mechanorezeptoren auf das quasi-statische Gleichgewicht mittels zwei unterschiedlicher Abkühlverfahren untersucht: eine permanente Abkühlung durch eine thermische Plattform und konventionelle Eis-Pads. Es wurden der COP Gesamtweg, plantar Temperaturen und eine visuelle Analogskala (VAS) in Bezug auf subjektive Schmerzen analysiert. Untersuchung II hat gezeigt, dass eine konstante und steuerbare Abkühlung über die thermische Plattform der überlegene Ansatz in Bezug auf subjektiven Schmerz (VAS) und bzgl. des Erreichens und Erhaltens einer gewünschten Temperatur innerhalb der Messungen ist. Weiterhin wurde nur durch die Abkühlung mittels thermischer Plattform eine posturale Instabilität induziert, evident durch erhöhte COP Gesamtwege. Diese Instabilität wurde aufgrund der Beeinträchtigung der plantaren Sensibilität erwartet, was auf eine fehlende Kompensation durch andere Sinnessysteme hinzuweisen scheint. In Untersuchung III lag der Fokus auf der inter- und intra-Tag-Reliabilität dynamischer Gleichgewichtsantworten mittels des Posturomed-Trainingsgerätes. Im Allgemeinen wurden eine gute relative und absolute Reliabilität der COP Gesamtwege ermittelt. Dieses Ergebnis war von grundlegender Bedeutung, um die Nutzung des gleichen Setups für die folgenden dynamischen Gleichgewichtsmessungen (Untersuchung IV) zu ermöglichen. Anschließend wurden die Effekte einer Beeinträchtigung der plantaren Sensibilität mittels Abkühlung auf antizipatorische und kompensatorische Antworten des dynamischen Gleichgewichts (anhand unerwarteter Störungen des Gleichgewichts) in Untersuchung IV erforscht. COP und EMG Daten wurden verwendet, um die antizipatorischen und kompensatorischen Antworten des Gleichgewichts zu analysieren. Nach der Abkühlung wurden bzgl. antizipatorischer Antworten keine Unterschiede in den COP und EMG Parametern gefunden. Im Hinblick auf kompensatorische Antworten zeigten sich reduzierte COP und EMG als Reaktion auf die Abkühlung. Dies wurde wie folgt interpretiert: aufgrund eines vorsichtigen Verhaltens, ausgelöst durch die verminderten sensorischen Inputs infolge der Abkühlung, kam es zu einer Art „Überkompensierungsverhalten“ des zentralen Nervensystems (ZNS). Schließlich stellte sich die Frage der Interaktion afferenter Rezeptoren in Untersuchung V, in welcher die Effekte reduzierter plantarer Temperaturen auf den Achillessehnen-Dehnungsreflex und die Plantarflexion untersucht wurden. Kurze Latenz Antworten (short latency responses) und die maximale Kraft der Plantarflexion wurden dabei analysiert. Die Abkühlung führte zu einer verminderten Amplitude der short latency responses sowie zu Verzögerungen der Zeit bis zur maximalen Kraft der Plantarflexion. Diese Ergebnisse deuten darauf hin, dass plantare Inputs in komplementärer Weise am Achillessehnen-Dehnungsreflex beteiligt sind. Zusammenfassend lässt sich aussagen, dass die vorliegende Arbeit zum Verständnis beiträgt, wie plantare Rezeptoren an der Bewegungssteuerung beteiligt sind. Es scheint, dass diese nicht nur in unabhängiger Form zur Bewegungssteuerung beitragen, sondern dabei auch mit anderen afferenten Rezeptoren interagieren. Darüber hinaus ist ein wichtiges Resultat, dass die reduzierten plantaren Inputs scheinbar verschiedene Änderungen in der Organisation von Ein- und Ausgängen im ZNS induzieren. Dies erfolgt anhand unterschiedlicher Anforderungen an das Gleichgewicht: quasi-statische Antworten, antizipatorische Antworten und kompensatorischen Antworten. Für die Zukunft könnte die Implementierung anderer Methoden, wie Mikroneurographie und Elektroenzephalographie, hilfreich sein, um noch mehr Verständnis bezüglich afferenter Interaktionen während der Kontrolle von Bewegungen erlangen zu können. Ähnliche Protokolle könnten auch in anderen Populationen durchgeführt werden, wie ältere Menschen oder Patienten mit neurologischen Erkrankungen, die einen kontinuierlichen Rückgang oder Degenerationen sensorischer Rezeptoren zeigen.

A manutenção do equilíbrio depende da ativação sinérgica de músculos dos dois hemicorpos, e há evidências de que essa coordenação é mediada por circuitos medulares, que estão sob controle supra-segmentar. O objetivo desse trabalho é descrever mecanismos neurofisiológicos e biomecânicos envolvidos no controle postural de sujeitos saudáveis frente a uma perturbação provocada por uma contração reflexa, enfatizando-se os mecanismos associados à coordenação entre membros. A perturbação postural ocorreu em resposta a um estímulo elétrico unilateral no nervo tibial. Devido a restrições em estudos anteriores, utilizou-se uma ampla abordagem (múltiplos músculos, reflexos cruzados) e estimulação precisamente controlada. Os resultados mostraram um complexo padrão de ativação dos músculos dos membros inferiores bilateralmente. Logo após o estímulo, foram encontradas respostas de curta e média latência em músculos da perna e da coxa. Posteriormente, foram observadas algumas ações musculares de longa latência nos músculos mais distais, que provavelmente foram ativadas em resposta às oscilações posturais. As respostas musculares iniciais sugerem que as informações aferentes e os reflexos medulares possuem uma função muito importante na regulação da coordenação entre membros, durante a manutenção da postura ereta quieta. / Balance depends on the synergic activation of muscles bilaterally, and there is evidence that this coordination is mediated by spinal circuits, which are under supra-spinal control. The objective of this study is to describe neurophysiologic and biomechanical mechanisms involved in the postural control of healthy subjects submitted to a disturbance provoked by a muscular reflex contraction. The postural perturbation was caused by a unilateral electric stimulation to the popliteal fossa. The analysis emphasizes the mechanisms associated with interlimb coordination. In this work, methodological approaches expanded those of previous work, the recordings being done bilaterally and the stimulus being precisely controlled. The results showed a complex pattern of bilateral muscular activation. Short and medium latency responses were found in the leg and thigh muscles. These were followed by some muscular activity at longer latencies, probably occurring due to the postural oscillations. The initial muscular responses suggest that the afferent inflow and the spinal cord reflexes have an important function in the between-limb coordination during the standing posture.