Effects of overground walking with a robotic exoskeleton on lower limb muscle synergies

Les exosquelettes robotisés de marche (ERM) représentent une intervention prometteuse dans le domaine de la réadaptation locomotrice. Sur le plan clinique, les ERM facilitent la mise en application de principes de neuroplasticité. Jusqu'à présent, la majorité des études analysant les effets de l’ERM a été menée avec des ERM fournissant une assistance robotique complète le long d’une trajectoire de mouvements prédéfinie des membres inférieurs (MI) de façon à reproduire la marche de façon quasi parfaite à très basse vitesse. La nouvelle génération d’ERM, maintenant disponible sur le marché, propose de nouveaux modes de contrôles qui permettent, entre autres, une liberté de mouvement accrue aux MIs (c.-à-d. trajectoire non imposée) et une possibilité d’offrir une assistance ou résistance aux mouvements de différentes intensités surtout pendant la phase d’oscillation du cycle de marche. Cependant, les effets de ces modes de contrôles sur la coordination musculaire des MI pendant la marche au sol avec l’ERM, caractérisé via l’extraction de synergies musculaires (SM), restent méconnus. Cette thèse mesure et compare les caractéristiques des SM (c.-à-d. nombre, profils d’activation, composition musculaire et contribution relative des muscles) pendant la la marche au sol sans ou avec un ERM paramétré avec six différents modes de contrôle chez des individus en bonne santé (articles #1 et #2) et d’autres ayant une lésion médullaire incomplète (LMI) (article #3). Les signaux électromyographiques (EMG) des différents muscles clés des MI, enregistrés lors de la marche, ont été utilisés afin d’extraire les SM avec un algorithme de factorisation matricielle non négative. La similarité des cosinus et les coefficients de corrélation ont caractérisé les similitudes entre les caractéristiques des SM. Les résultats montrent que: 1) les profils d'activation temporelle et le nombre de SM sont modifiés en fonction de la vitesse de marche avec, entre autres une augmentation de la vitesse de marche entrainant une fusion de SM, chez les individus en bonne santé marchant sans ERM ; 2) lorsque ces derniers marchent avec un ERM, les différents modes de contrôle testés ne dupliquent pas adéquatement les SM retrouvées lors de la marche sans ERM. En fait, uniquement le mode de contrôle libérant la contrainte de trajectoire de mouvements des MIs dans le plan sagittal lors de la phase d’oscillation reproduit les principales caractéristiques des SM retrouvées pendant la marche sans ERM ; 3) le nombre et la composition musculaire des SM sont modifiés pendant la marche sans ERM chez les personnes ayant une LMI. Cependant, parmi tous les modes de contrôle étudiés, seul le mode de contrôle libérant le contrôle de la trajectoire de mouvements des MI et assistant l’oscillation du MIs (c.-à-d. HASSIST) permets l’extraction de SM similaire à celles observées chez des individus en santé lors d'une marche sans ERM. Dans l’ensemble, cette thèse a mis en évidence le fait que différentes demandes biomécaniques liées à la marche (c.-à-d. vitesse de marche, modes de contrôle de l’ERM) modifient le nombre et les caractéristiques de SM chez les personnes en santé. Cette thèse a également confirmé que la coordination musculaire, mise en évidence via l’analyse de SM, est altérée chez les personnes ayant une LMI et a tendance à se normaliser lors de la marche avec l’ERM paramétré dans le mode de HASSIST. Les nouvelles preuves appuieront les professionnels de la réadaptation dans le processus de prise de décision concernant la sélection du mode de contrôle des MIs lors de l’entrainement locomoteur utilisant avec un ERM.Wearable robotic exoskeletons (WRE) represent a promising rehabilitation intervention for locomotor rehabilitation training that aligns with activity-based neuroplasticity principles in terms of optimal sensory input, massed repetition, and proper kinematics. Thus far, most studies that investigated the effects of WRE have used WRE that provide full robotic assistance and fixed trajectory guidance to the lower extremity (L/E) to generate close-to-normal walking kinematics, usually at very slow speeds. Based on clinicians’ feedback, current commercially-available WRE have additional control options to be able to integrate these devices into the recovery process of individuals who have maintained some ability to walk after an injury to the central nervous system. In this context, WRE now offer additional degrees of movements for the L/E to move freely and different strategies to assist or resist movement, particularly during the gait cycle’s swing phase. However, the extent that these additional WRE control options affect L/E neuromuscular control during walking, typically characterized using muscle synergies (MSs), remains unknown. This thesis measures and compares MSs characteristics (i.e., number, temporal activation profile, and muscles contributing to a specific synergy [weightings]) during typical overground walking, with and without a WRE, in six different control modes, in abled-bodied individuals (Articles #1 and #2) and individuals with incomplete spinal cord injury (iSCI; Article #3). Surface EMG of key L/E muscles were recorded while walking and used to extract MSs using a non-negative matrix factorization algorithm. Cosine similarity and correlation coefficients characterized, grouped, and indicated similarities between MS characteristics. Results demonstrated that: 1) the number of MSs and MS temporal activation profiles in able-bodied individuals walking without WRE are modified by walking speed and that, as speed increased, specific MSs were fused or merged compared to MSs at slow speeds; 2) In able-bodied individuals walking with WRE, few WRE control modes maintained the typical MSs characteristics that were found during overground walking without WRE. Moreover, freeing the L/E swing trajectory imposed by the WRE best reproduced those MSs characteristics during overground walking without the WRE; and 3) After an iSCI, alterations to the number and the composition of MSs were observed during walking without WRE. However, of all WRE control modes that were investigated, only HASSIST (i.e., freeing WRE control over L/E swing trajectory while assisting the user’s self-selected trajectory) reproduced the number and composition of MSs found in abled-bodied individuals during overground walking without WRE. Altogether, the results of this thesis demonstrated that different walking-related biomechanical demands (i.e., walking speed) and most of the WRE control modes can alter some MSs, and their characteristics, in able-bodied individuals. This research also confirmed that impaired muscle coordination, assessed via MSs, can adapt when walking with a WRE set with specific control options (e.g., HASSIST). These MS adaptations mimicked typical MS characteristics extracted during overground walking. The evidence generated by this thesis will support the decision-making process when selecting specific L/E control options during WRE walking, allowing rehabilitation professionals to refine WRE locomotor training protocols

Multi-Task Neuromuscular Generalization and Changes Through the Lifespan

Mobility in everyday life requires executing and shifting between a broad assortment of functional tasks and resisting disturbances that could cause falls. Though the importance of successfully performing a variety of functional tasks is recognized and incorporated in clinical assessments (e.g., the Timed-Up-and-Go Test, Berg Balance Scale), little is understood about the underlying neuromuscular control required, or how it changes with age. The neuromuscular control for functional tasks such as walking is typically studied in isolation, or with variations on the same task. Characterizing the coordination required to produce and shift between a wider variety of tasks and resist external disturbances is crucial to understanding mobility in daily life, not just within a controlled lab environment. In this work, we identify patterns of multi-muscle coordination (motor modules) across functional tasks in healthy young, middle-aged, and older adults. We demonstrate that healthy young adults recruit common motor modules across voluntary functional tasks (walking, turning, and chair transfers), and characterize changes associated with age. Additionally, we investigate whether motor modules are shared between reactive balance and these voluntary tasks, and whether there are age-related changes here. Identifying age-related changes in multi-muscle coordination can lead to a better understanding of the neuromuscular control underlying mobility changes due to normal aging. Further, fully characterizing changes in neuromuscular control that are due to normal aging can provide a basis for identifying the changes associated with impairments that commonly occur in older adults (e.g., stroke)

Muscle synergy analysis of lower-limb movements

Dissertação de mestrado integrado em Biomedical Engineering (área de especialização em Medical Electronics)Neurological disorders and trauma often lead to impaired lower-limb motor coordination. Understanding how muscles combine to produce movement can directly benefit assistive solutions to those afflicted with these impairments. A theory in neuromusculoskeletal research, known as muscle synergies, has shown promising results in applications for this field. This hypothesis postulates that the Central Nervous System controls motor tasks through the time-variant combinations of modules (or synergies), each representing the co-activation of a group of muscles. There is, however, no unifying, evidence-based framework to ascertain muscle synergies, as synergy extraction methods vary greatly in the literature. Publications also focus on gait analysis, leaving a knowledge gap when concerning motor tasks important to daily life such as sitting and standing. The purpose of this dissertation is the development of a robust, evidence-based, task-generic synergy extraction framework unifying the divergent methodologies of this field of study, and to use this framework to study healthy muscle synergies on several activities of daily living: walking, sit-to-stand, stand-to-sit and knee flexion and extension. This was achieved by designing and implementing a cross-validated Non-Negative Matrix Factorization process and applying it to muscle electrical activity data. A preliminary study was undertaken to tune this configuration regarding cross-validating proportions, data structuring prior to factorization and evaluating criteria quantifying accuracy in modularity findings. Muscle synergies results were then investigated for different performing speeds to determine if their structure differed, and for consistency across subjects, to ascertain if a common set of muscle synergies underlay control on all subjects equally. Results revealed that the implemented framework was consistent in its ability to capture modularity (p < 0:05). The movements’ synergies also did not differ across the studied range of speeds (except one module in Knee Flexion) (p < 0:05). Additionally, a common set of muscle synergies was present across several subjects (p < 0:05), but shared commonality across every participant was only observed for the walking trials, for which much larger amounts of data were collected. Overall, the established framework is versatile and applicable for different lower-limb movements; muscle synergies findings for the examined movements may also be used as control references in assistive devices.As perturbações e traumas neurológicos afetam frequentemente a coordenação motora dos membros inferiores. Uma teoria recente em investigação neuromusculo-esquelética, denominada de sinergias musculares, tem demonstrado resultados promissores em soluções de assistência à população afetada por estes distúrbios. Esta teoria propõe que o Sistema Nervoso Central controla as tarefas motoras através de combinações variantes no tempo de módulos (ou sinergias), sendo que cada um representa a co-ativação de um grupo de músculos. No entanto, não existe nenhum processo uniformizante, empiricamente justificado para determinar sinergias musculares, porque os métodos de extração de sinergias variam muito na literatura. Para além disso, as publicações normalmente focam-se em análise da marcha, deixando uma lacuna de conhecimento em tarefas motoras do dia-a-dia, tais como sentar e levantar. O objetivo desta dissertação é o desenvolvimento de um processo robusto, genérico e empiricamente justificado de extração de sinergias em várias tarefas motoras, unindo as metodologias divergentes neste campo de estudo, e subsequentemente utilizar este processo para estudar sinergias musculares de sujeitos saudáveis em várias atividades do dia-a-dia: marcha, erguer-se de pé partir de uma posição sentada, sentar-se a partir de uma posição de pé e extensão e flexão do joelho. Isto foi alcançado através da implementação de um processo de cross-validated Non-Negative Matrix Factorization e subsequente aplicação em dados de atividade elétrica muscular. Um estudo preliminar foi realizado para configurar este processo relativamente às proporções de cross-validation, estruturação de dados antes da fatorização e seleção de critério que quantifique o sucesso da representação modular dos dados. Os resultados da extração de sinergias de diferentes velocidades de execução foram depois examinados no sentido de descobrir se este fator influenciava a estrutura dos módulos motores, assim como se semelhanças entre as sinergias de diferentes sujeitos apontavam para um conjunto comum de sinergias musculares subjacente ao controlo do movimento. Os resultados revelaram que o processo implementado foi consistente na sua capacidade de capturar a modularidade nos dados recolhidos (p < 0:05). As sinergias de todos os movimentos também não diferiram para toda a gama de velocidades estudada (exceto um módulo na flexão do joelho) (p < 0:05). Por fim, um conjunto comum de sinergias musculares esteve presente em vários sujeitos (p < 0:05), mas só esteve presente em todos os sujeitos de igual forma para a marcha, para a qual a quantidade de dados recolhida foi muito maior. Globalmente, o processo implementado é versátil e aplicável a diferentes movimentos dos membros inferiores; os resultados das sinergias musculares para os movimentos examinados podem também ser utilizado como referências de controlo para dispositivos de assistência

Fifteen years of wireless sensors for balance assessment in neurological disorders

Balance impairment is a major mechanism behind falling along with environmental hazards. Under physiological conditions, ageing leads to a progressive decline in balance control per se. Moreover, various neurological disorders further increase the risk of falls by deteriorating specific nervous system functions contributing to balance. Over the last 15 years, significant advancements in technology have provided wearable solutions for balance evaluation and the management of postural instability in patients with neurological disorders. This narrative review aims to address the topic of balance and wireless sensors in several neurological disorders, including Alzheimer's disease, Parkinson's disease, multiple sclerosis, stroke, and other neurodegenerative and acute clinical syndromes. The review discusses the physiological and pathophysiological bases of balance in neurological disorders as well as the traditional and innovative instruments currently available for balance assessment. The technical and clinical perspectives of wearable technologies, as well as current challenges in the field of teleneurology, are also examined

How visual perceptual grouping influences foot placement

Everybody would agree that vision guides locomotion; but how does vision influence choice when there are different solutions for possible foot placement? We addressed this question by investigating the impact of perceptual grouping on foot placement in humans. Participants performed a stepping stone task in which pathways consisted of target stones in a spatially regular path of foot falls and visual distractor stones in their proximity. Target and distractor stones differed in shape and colour so that each subset of stones could be easily grouped perceptually. In half of the trials, one target stone swapped shape and colour with a distractor in its close proximity. We show that in these ‘swapped’ conditions, participants chose the perceptually groupable, instead of the spatially regular, stepping location in over 40% of trials, even if the distance between perceptually groupable steps was substantially larger than normal step width/length. This reveals that the existence of a pathway that could be traversed without spatial disruption to periodic stepping is not sufficient to guarantee participants will select it and suggests competition between different types of visual input when choosing foot placement. We propose that a bias in foot placement choice in favour of visual grouping exists as, in nature, sudden changes in visual characteristics of the ground increase the uncertainty for stability

The Effects of Partial Body Weight Support for Gait for Patients with Neurological Dysfunction: A Case Study Approach

The purpose of this study was to determine the effects of partial body weight support during gait for individuals with neurological dysfunction. Body weight support (BWS) training provides a safe environment in which the individual can perform and practice mechanics of normal gait at a variety of speeds with or without body weight support, depending on the level of function. The subjects who participated in this study were community ambulators older than 20 years of age with a neurological diagnosis. Each subject was tested initially and at the conclusion of the study to compare data using a battery of balance and gait tests. Each subject participated in body weight support treadmill gait training using the LiteGaitTM three times a week for up to six weeks. Each subject was to begin with 40% body weight support (BWS) and a treadmill speed of .5 mph, progress to 20% BWS and a speed of .7 mph, and finally to 0% BWS and a speed of 1.0 mph. All three subjects made improvements when comparing initial to final testing results. Many factors may have limited the results of our study including the tester, sensitivity of the tests performed, or sudden changes in medical status

Moving out of the lab:movement analyses in patients with osteoarthritis of the knee

Osteoarthritis of the knee is one of the main causes of physical limitations. In addition to osteoarthritis, obesity is also a growing public health problem. Research has shown that obese people are almost four times as likely to develop osteoarthritis of the knee. Patients with osteoarthritis of the knee develop compensation mechanisms during daily activities. This dissertation focuses on the analysis of biomechanical components in patients with osteoarthritis of the knee. The focus was on the knee adduction moment (KAM) during walking, stair climbing and sit-to-stand. A high KAM is associated with the onset and progression of osteoarthritis of the knee. Furthermore, this study focused on physical activity in patients with osteoarthritis of the knee with and without obesity. In this way, this research wanted to gain more insight into small changes in movement behaviour in these patients. Accelerometery is a good way to understand quantity and quality of physical activity. Patients with both osteoarthritis of the knee and obesity have a significantly increased KAM compared to healthy subjects. However, presence of only osteoarthritis of the knee, does not result in an increased KAM. Furthermore, more insight was gained into the actual physical activity and limitations in daily life in patients with osteoarthritis of the knee

Does practice of multi-directional stepping with auditory stimulation improve movement performance in patients with Parkinson\u27s disease

Parkinson’s disease (PD) is a debilitating neurodegenerative disorder causing many physical limitations. Rhythmic auditory stimulation (RAS) influences motor complications not alleviated by medicine and has been used to modify straight line walking in this population. However, motor complications are exacerbated during more complex movements including those involving direction changes. Thus immediate RAS effects on direction switch duration (DSD) and other kinematic measures during a multi-directional step task were investigated in PD patients. Long term RAS application was also explored by evaluating functional gait and balance and kinematic step measures before and after 6 weeks of multi-directional stepping either with (Cue, C group) or without (No cue, NC group) RAS use. Evaluations were also administered 1, 4 and 8 weeks after training termination. Kinematic measures were collected during stepping without, then with RAS for the C group and without RAS for the NC group. Step testing/training was performed at slow, normal and fast speeds in forward, back and side directions. Participants with PD switched step direction during the stepping task faster with RAS use before training. Like straight line walking RAS application influenced the more complex task of direction switching and counteracted the well-known bradykinesia in PD. After training both groups improved their functional gait and balance measures and maintained balance improvements for at least 8 weeks. Only the C group retained gait improvements for at least 8 weeks after training termination. Adding RAS resulted in functional benefits not observed in training without it. Kinematic measures compared before and after step training clarified the underlying contributors to functional performances. Both groups reduced the variability of DSD. The C group participants maintained this alteration longer. DSD reduction also occurred after training and was retained for at least 8 weeks for this group. These outcomes further support the advantages of adding RAS to training regiments for those with PD. The current results indicate that RAS effects are not limited to simple activities like straight line walking. Moreover, RAS can be used for improving and maintaining improvements longer in activities involving various forms of transition which present most difficulties for those with PD