Search

Background: Hemiparetic gait is characterized by strong asymmetries that can severely affect the quality of life of stroke survivors. This type of asymmetry is due to motor deficits in the paretic leg and the resulting compensations in the nonparetic limb. In this study, we aimed to evaluate the effect of actively promoting gait symmetry in hemiparetic patients by assessing the behavior of both paretic and nonparetic lower limbs. This paper introduces the design and validation of the REFLEX prototype, a unilateral active knee–ankle–foot orthosis designed and developed to naturally assist the paretic limbs of hemiparetic patients during gait. Methods: REFLEX uses an adaptive frequency oscillator to estimate the continuous gait phase of the nonparetic limb. Based on this estimation, the device synchronically assists the paretic leg following two different control strategies: (1) replicating the movement of the nonparetic leg or (2) inducing a healthy gait pattern for the paretic leg. Technical validation of the system was implemented on three healthy subjects, while the effect of the generated assistance was assessed in three stroke patients. The effects of this assistance were evaluated in terms of interlimb symmetry with respect to spatiotemporal gait parameters such as step length or time, as well as the similarity between the joint’s motion in both legs. Results: Preliminary results proved the feasibility of the REFLEX prototype to assist gait by reinforcing symmetry. They also pointed out that the assistance of the paretic leg resulted in a decrease in the compensatory strategies developed by the nonparetic limb to achieve a functional gait. Notably, better results were attained when the assistance was provided according to a standard healthy pattern, which initially might suppose a lower symmetry but enabled a healthier evolution of the motion of the nonparetic limb. Conclusions: This work presents the preliminary validation of the REFLEX prototype, a unilateral knee exoskeleton for gait assistance in hemiparetic patients. The experimental results indicate that assisting the paretic leg of a hemiparetic patient based on the movement of their nonparetic leg is a valuable strategy for reducing the compensatory mechanisms developed by the nonparetic limb., This research was funded by the Spanish Ministry of Science and Innovation, project Discover2Walk (PID2019-105110RB-C31), and the Programas de Actividades I+D en la Comunidad de Madrid and Structural Funds of the EU (Robocity, S2018/NMT-4331). J.S. L-M. received a Training Program for Academic Staff fellowship (FPU16/01313) from the Ministry of Universities of the Government of Spain.

Background: Functional limitations after a stroke are unique to each person and often include impaired independent mobility. A reduction in existing gait deficits after a stroke is often one of the main goals of rehabilitation. Gait re-education after stroke is a complex process, which consists of the effects of many therapeutic interventions. Objective: The study aimed to analyze the effects of using a treadmill with visual feedback in gait re-education in the sub-acute stroke period and assess the impact of biofeedback treadmill training on selected gait parameters, improving static balance and reducing the need for orthopedic aids. Methods: The study included 92 patients (F: 45, M: 47) aged 63 ± 12 years, with post-ischemic sub-acute (within six months onset) stroke hemiparesis, treated at a neurological rehabilitation ward. All patients participated in a specific rehabilitation program, and in addition, patients in the study group (n = 62) have a further 10 min of treadmill training with visual feedback. Patients in the control group (n = 30) participated in additional conventional gait training under the direct supervision of a physiotherapist. The evaluation of static balance was assessed with the Romberg Test. A Biodex Gait Trainer 3 treadmill with biofeedback function was used to evaluate selected gait parameters (walking speed, step length, % limb loading, and traveled distance). The use of an orthopedic aid (walker or a crutch) was noted. Results: After four weeks of rehabilitation, step length, walking speed, traveled distance, and static balance were significantly improved for the study and control group (p < 0.05). Treadmill gait training yielded significantly better results than a conventional rehabilitation program. Only the study group observed a corrected walking base (p < 0.001). All participants showed a reduction in the use of walking aids (p = 0.006). There was no asymmetry in the % of limb loading for either group prior to or following rehabilitation. Conclusions: The treadmill with visual biofeedback as conventional gait training has resulted in a significant improvement in parameters such as step length, walking speed, static balance, and a reduction in the use of locomotion aids. However, the achieved improvement in gait parameters is still not in line with the physiological norm.

This bachelor thesis deals with influence of botulinum toxin and for walking in hemiparetic patient (spastic hemiparesis after stroke). In the theoretical part, the problem of stroke an one of the very common diseases that cause central hemiparesis is approached from the beginning. Further, spasticity and its treatment are described here. The last part deals with the issue of hemiparetic gait and its rehabilitation. The main goal of the work was to record possible changes in gait parameters during the application of botulinum toxin A, which is applied every 3 months. The research involved 2 probands from regional spasticity center of the Hospital of Czech Budweis a.s., with central hemiparesis after stroke. They underwent entrance (2-3 weeks after application botulinum toxin) and exit examinations (1-2 weeks before application botulinum toxin), which consisted of kinesiological examination, examination of spastic paresis hip dysplasia according to the procedure J.M. Graciese, selected clinical gait tests (TUG, 2MWT), EMG examination and postural stability test (WBS). The whole measurements were performed to see, if any changes during the action of botulinum toxin could be objectifield, either clinically or by surface EMG. The obtained results were quite individual, bit despire a very small group of proband, it was possible to follow certain trends influence botulinum toxin. Surface electromyography has proven to be a suitable tool for monitoring muscle activity, but for future similar studies,will be need many more probands and repeat measurements to be include.

Impairments in walking speed, capacity, and endurance are commonly seen after stroke. Treadmill training improves endurance and gait speed. However, the lack of variable training speed and automated speed progression increases the risk of backward displacement and falling. An automated, speed-sensing treadmill prototype with partial body weight support, the Variable Automated Speed and Sensing Treadmill II (VASST II), was tested in an outpatient rehabilitation setting. Eleven subacute or chronic hemiplegics who could ambulate at > 0.2 m/s for >50 m participated in the study. All subjects underwent physiotherapist-supervised training on VASST II for 60 min daily, 3 times per week, for 5 weeks (total 15 h). Outcome measures at Week 3 (mid-VASST II training), Week 6 (post-VASST II training), Week 12 (first follow-up), and Week 24 (second follow-up) included the 6 minute walk test (6 MWT), 10 meter walk test (10 MWT), Berg Balance Scale (BBS) score, and Functional Ambulation category (FAC) score. User acceptability of VASST II for both study subjects and physiotherapists were also assessed. All subjects [median (IQR) age: 53.0 (22) years; median (IQR) duration post-stroke: 524 (811) days] completed VASST II training. At baseline, mean ± SD 6 MWT was 114 ± 50.9 m; mean ± SD 10 MWT was 0.37 ± 0.18 m/s; mean ± SD BBS score was 40 ± 10; and, mean ± SD FAC score was 4 ± 1. At Week 6, there were significant improvements in the 6 MWT [158.91 ± 88.69 m; P = 0.003], 10 MWT [0.49 ± 0.30 m/s; P = 0.016], and BBS score [42 ± 10; P = 0.003]. Improvements in 6 MWT and BBS scores were sustained at Week 24, but not in the 10 MWT. No VASST II-training related falls were reported. All subjects rated their VASST II training positively and indicated that it improved their current walking ability. VASST II training was effective, feasible, and safe in patients with subacute or chronic post-stroke hemiparetic gait, with sustained gains in distance walked (6 MWT) and functional balance (BBS score) up to 19 weeks post-intervention.

In order to assist after-stroke individuals with hemiparetic gait pattern to rehabilitate their movements, many research centers have developed exoskeletons for lower limbs and control strategies for them. The present work aims to develop a robotic control strategy based on kinetic motor primitives capable of assisting the recovery of patients with compromised movements. The joint positions of a healthy subject walking on a treadmill, wearing and not wearing a six degree- of-freedom exoskeleton, were obtained through IMUs (Inertial Measurements Units) and used to calculate the joint torques using the OpenSim software. Motor primitives of the kinetic data (torques), and their respective weights, were then computed using Principal Component Analysis (PCA). Based on the ratio of the weights, a control strategy was designed to generate the necessary robot torque in order to assist the individual during the walking wearing the exoskeleton. The proposed strategy was evaluated with the subject wearing a torque-controlled orthosis for 120 seconds at 1.5 km/h on a treadmill. The torques and angles of the individual were obtained for posterior analysis.

Post-stroke gait dysfunction occurs at a very high prevalence. A practical method to quantitatively analyze the characteristics of hemiparetic gait is needed in both clinical and community settings. This study developed a 10-channeled textile capacitive pressure sensing insole (TCPSI) with a real-time monitoring system and tested its performance through hemiparetic gait pattern analysis. Thirty-five subjects (18 hemiparetic, 17 healthy) walked down a 40-m long corridor at a comfortable speed while wearing TCPSI inside the shoe. For gait analysis, the percentage of the plantar pressure difference (PPD), the step count, the stride time, the coefficient of variation, and the phase coordination index (PCI) were used. The results of the stroke patients showed a threefold higher PPD, a higher step count (41.61 &plusmn, 10.7), a longer average stride time on the affected side, a lower mean plantar pressure on the affected side, higher plantar pressure in the toe area and the lateral side of the foot, and a threefold higher PCI (hemi: 19.50 &plusmn, 13.86%, healthy: 5.62 &plusmn, 5.05%) compared to healthy subjects. This study confirmed that TCPSI is a promising tool for distinguishing hemiparetic gait patterns and thus may be used as a wearable gait function evaluation tool, the external feedback gait training device, and a simple gait pattern analyzer for both hemiparetic patients and healthy individuals.

Quantitative evaluation of the hemiparesis status for a poststroke patient is still challenging. This study aims to measure and investigate the dynamic muscle behavior in poststroke hemiparetic gait using ultrasonography. Twelve hemiparetic patients walked on a treadmill, and EMG, joint angle, and ultrasonography were simultaneously recorded for the gastrocnemius medialis muscle. Pennation angle was automatically extracted from ultrasonography using a tracking algorithm reported previously. The characteristics of EMG, joint angle, and pennation angle in gait cycle were calculated for both (affected and unaffected) sides of lower limbs. The results suggest that pennation angle could work as an important morphological index to continuous muscle contraction. The change pattern of pennation angle between the affected and unaffected sides is different from that of EMG. These findings indicate that morphological parameter extracted from ultrasonography can provide different information from that provided by EMG for hemiparetic gait.

RESUMO O modelo de brace desenvolvido consiste em uma joelheira de neoprene que apresenta um balonete inflável posicionado sobre a região poplítea do joelho. Ele proporciona estímulos sobre estruturas articulares, bem como um melhor alinhamento biomecânico durante a fase de apoio da marcha. O objetivo do estudo foi quantificar as alterações e adaptações induzidas pelo treinamento da marcha com a utilização do dispositivo ortótico em pacientes hemiparéticos. Realizou-se um estudo quase-experimental do tipo antes e depois com doze pacientes adultos com hemiparesia decorrente de acidente vascular encefálico. Os picos de pressão plantares foram os marcadores utilizados para comparar os três momentos do estudo: na linha de base, quando estivessem utilizando o brace e após o treinamento da marcha. Depois das sessões de reeducação da marcha com auxílio da órtese, a redistribuição das pressões plantares evidenciou aumento na simetria durante a fase de apoio, principalmente pela diminuição da pressão sobre o antepé parético (p=0,024) e pelo aumento no retropé no lado parético (p=0,010). Além disso, essas alterações foram associadas a uma diminuição da pressão sobre todas as regiões do pé não afetado, especialmente no retropé no momento de pós-treinamento. Os resultados do estudo sugerem uma mudança no padrão de marcha dos participantes depois da utilização do brace. Houve maior simetria dos valores dos picos de pressão plantar quando se comparou o lado afetado com o não afetado. O treino com o brace contribui no processo de reabilitação, uma vez que forneceu valores baropodométricos que se aproximaram ao padrão normal de distribuição plantar. RESUMEN En una rodillera de neoprene se desarrolló un tipo de rodillera ortopédica, que lleva un manguito inflable, puesto en la región poplítea de la rodilla, y que les proporciona estímulos a las estructuras articulares, así como mejora la alienación biomecánica durante la fase de apoyo de la marcha. El propósito del estudio es cuantificar las alteraciones y adaptaciones producidas por el entrenamiento con este dispositivo ortótico en pacientes hemiparéticos. Se trata de un estudio casi experimental de tipo antes y después, del cual participaron doce adultos hemiparéticos debido al accidente cerebrovascular. Se utilizaron como marcadores los picos de presión plantar para comparar tres momentos del estudio: el inicio del estudio; el momento en que utilizaban la rodillera y tras entrenar la marcha. Después de las sesiones de rehabilitación de la marcha con ayuda de la rodillera, en la redistribución de las presiones plantares ocurrió un aumento en la simetría durante la fase de apoyo, principalmente disminución de la presión sobre el antepié parético (p=0,024) y aumento en el retropié en el lado parético (p=0,010). Además, estas alteraciones se las asociaron a la disminución de la presión sobre todas las regiones del pie no alterado, especialmente en el retropié en el momento posterior al tratamiento. Los resultados del estudio muestran un cambio en el patrón de marcha de los participantes después de utilizar este tipo de rodillera. Hubo una mayor simetría de los valores de los picos de presión plantar cuando se comparó el lado alterado con el no alterado. El entrenamiento con este tipo de rodillera ayudó en el proceso de rehabilitación, puesto que presentó valores baropodométricos cerca del patrón prestablecido de distribución plantar. ABSTRACT The model of brace developed consists of a neoprene kneepad that has an inflatable cuff positioned over the popliteal region of the knee. It provides stimuli on joint structures as well as a better biomechanical alignment during the stance phase of the gait. The aim of this study was to quantify the changes and adaptations induced by gait training with the use of orthotic device in hemiparetic patients. A quasi-experimental before-after study was held with twelve adult patients with hemiparesis due to cerebrovascular accident. The peaks of plantar pressure were the markers used to compare the three moments of the study: the baseline, when they were using the brace, and post-gait training. After the sessions of gait retraining with the orthosis, the redistribution of plantar pressures showed increased symmetry during the stance phase, mainly by reducing the pressure on the paretic forefoot (p=0.024) and by the increase in the rearfoot in the paretic side (p=0.010). In addition, these changes were associated with a decrease in pressure on all regions of the foot not affected, especially in the rearfoot after training. The results of the study suggest a change in the gait pattern of participants after using the brace. There has been greater symmetry of the values of the plantar pressure peaks when the affected side was compared with the nonaffected side. Training with the brace helps in the rehabilitation process, since it provides baropodometric values approaching the normal pattern of plantar distribution.

Stroke survivors often have a slow, asymmetric walking pattern. They also walk with a higher metabolic cost than healthy, age-matched controls. It is often assumed that spatial-temporal asymmetries contribute to the increased metabolic cost of walking poststroke. However, elucidating this relationship is made challenging because of the interdependence between spatial-temporal asymmetries, walking speed, and metabolic cost. Here, we address these potential confounds by measuring speed-dependent changes in metabolic cost and implementing a recently developed approach to dissociate spatial versus temporal contributions to asymmetry in a sample of stroke survivors. We used expired gas analysis to compute the metabolic cost of transport (CoT) for each participant at 4 different walking speeds: self-selected speed, 80% and 120% of their self-selected speed, and their fastest comfortable speed. We also computed CoT for a sample of age- and gender-matched control participants who walked at the same speeds as their matched stroke survivor. Kinematic data were used to compute the magnitude of a number of variables characterizing spatial-temporal asymmetries. Across all speeds, stroke survivors had a higher CoT than controls. We also found that our sample of stroke survivors did not choose a self-selected speed that minimized CoT, contrary to typical observations in healthy controls. Multiple regression analyses revealed negative associations between speed and CoT and a positive association between asymmetries in foot placement relative to the trunk and CoT. These findings suggest that interventions designed to increase self-selected walking speed and reduce foot-placement asymmetries may be ideal for improving walking economy poststroke.

The toe clearance of a paretic limb in the swing phase of gait is related to tripping, which is considered a major cause of falls. The biomechanical factors for obtaining toe clearance are more complicated in hemiparetic gait than that in normal gait because of the compensatory movements during swing phase. Understanding the biomechanical factors should help in targeting the point for rehabilitative interventions.To clarify the biomechanical factors behind toe clearance during swing phase in hemiparetic gait.Fifty patients with hemiparesis after a stroke participated in this study. Three-dimensional motion analysis was used for the kinematic analysis of the hemiparetic gait. The correlation coefficients between limb shortening and angle changes and between limb shortening and hip elevation and foot lateral shift were calculated. Limb shortening was defined as the shortening of the hip-toe distance. The significant factors that determine toe clearance were examined by multiple regression analysis. Independent variables were limb shortening, hip elevation, and foot lateral shift.Limb shortening was negatively correlated with hip elevation (r = -0.75) and foot lateral shift (r = -0.41). Multiple regression analysis showed a significant contribution of limb shortening and hip elevation to toe clearance. The coefficient of determination was 0.95.Toe clearance was mainly determined by limb shortening and hip elevation, which were found to be in a trade-off relationship. These results warrant further investigation into the use of three-dimensional motion analysis in the rehabilitation clinic to facilitate targeted rehabilitative training to restore gait ability.

Данная работа посвящена биомеханическому и электромиографическому обоснованию применения фазовой электрической стимуляции мышц у детей с гемипаретической формой ДЦП (форма детского церебрального паралича, при которой двигательные расстройства более выражены в одной стороне тела). Под наблюдением находились две группы детей с данной формой ДЦП различного возраста 8-10 лет (13 детей) и 13-14 лет (12 детей). Наши исследования показали, что возраст у данного контингента больных имеет принципиальное значение при разработке различных реабилитационных программ, в том числе программы фазовой электрической стимуляции мышц при ходьбе. Ходьба детей обеих групп характеризуется снижением скорости, темпа и длины шага, уменьшением устойчивости, асимметрией временных, кинематических, динамических и электромиографических параметров. Тем не менее у больных первой группы отмечается бoльшая симметрия биомеханических и особенно электромиографических параметров. В частности, у них наблюдается общее симметричное снижение активности мышц нижних конечностей с акцентом на мышцы дистальных отделов ног. У больных второй группы оказывается сформированным более компенсированный вид гемипаретической походки, при которой дефект имеет отчетливый односторонний дистальный характер и в значительной мере возмещается усилением работы мышц проксимальных отделов нижних конечностей. Полученные результаты указывают на необходимость дифференцированного подхода к реабилитации детей с гемипаретической формой ДЦП в зависимости от возраста. В частности, реабилитация детей младше 10 лет должна осуществляться так же, как у детей с диплегической формой ДЦП (форма детского церебрального паралича, при которой наблюдается двусторонний паралич одноименных частей тела). В аспекте применения фазовой электрической стимуляции это означает, что основным воздействием является коррекция разгибания и отведения в обоих тазобедренных суставах посредством электрической стимуляции больших и средних ягодичных мышц. Данную коррекцию целесообразно сочетать со вспомогательными коррекциями, а именно с коррекцией тыльного сгибания в голеностопном суставе посредством электрической стимуляции передней большеберцовой мышцы. Основными объектами коррекции у детей с гемипаретической формой ДЦП старше 10 лет является разгибание и отведение в тазобедренном суставе и тыльное сгибание в голеностопном суставе только на паретичной нижней конечности. С нашей точки зрения, такой дифференцированный подход должен распространяться не только на метод фазовой электрической стимуляции мышц при ходьбе, но и на другие методы восстановления двигательных функций у детей с гемипаретической формой ДЦП разного возраста.This work is devoted to biomechanical and electromyographic foundation of application of phase electrical stimulation of muscles in children with hemiparetic form of infantile cerebral palsy. Two groups of children with this form of infantile cerebral palsy of different age were under consideration at the age of 8-10 (13 children) and at the age of 13-14 (12 children). Our investigations demonstrate that patientsۥ age is of the decisive significance in elaboration of different rehabilitation programs, including program of phase electrical stimulation of muscles during walking. Walking of children of both groups is characterized by reduction of walking velocity, cadence and step length, decrease of stability, asymmetry of the temporal, kinematic, dynamic and electromyographic parameters. Nevertheless, greater symmetry of the biomechanical and especially of electromyographic parameters is seen in the first group of patients. In particular, general symmetrical decrease of activity of muscles of the lower extremities with accent to the muscles of the distal segments is observed in patients of this group. More compensated type of hemiparetic gait is formed in patients of the second group. In this case, the defect has distinct unilateral distal character and is considerably compensated by strengthening of work of muscles of the proximal segments of the lower extremities. The received results point to the necessity of the differential approach to rehabilitation of children with hemiparetic form of infantile cerebral palsy in dependence on their age. In particular, rehabilitation of children younger 10 must be realized by the same way as in children with diplegic form of infantile cerebral palsy, i.e. in both legs. In aspect of application of phase electrical stimulation, that means that correction of extension and abduction at both of the hip joints by means of electrical stimulation of both of m. gluteus maximus and both gluteus medius is the main influence in this group of children. It is expedient to combine this correction with the subsidiary corrections, namely with correction of the dorsal flexion at the ankle joint by means of electrical stimulation of m. tibialis anterior. The following corrections are the main ones in children older 10: extension and abduction at the hip joint and dorsal flexion at the ankle joint, but only in the paretic lower extremity. From our point of view, such differential approach must be spread not only on the method of phase electrical stimulation of muscles during walking, but also on other methods of restoration of the motional functions during walking in patients with hemiparetic form of infantile cerebral palsy of different age.

There is an interest to identify factors facilitating locomotor adaptation induced by split-belt walking (i.e., legs moving at different speeds) because of its clinical potential. We hypothesized that augmenting braking forces, rather than propulsion forces, experienced at the feet would increase locomotor adaptation during and after split-belt walking. To test this, forces were modulated during split-belt walking with distinct slopes: incline (larger propulsion than braking), decline (larger braking than propulsion), and flat (similar propulsion and braking). Step length asymmetry was compared between groups because it is a clinically relevant measure robustly adapted on split-belt treadmills. Unexpectedly, the group with larger propulsion demands (i.e., the incline group) changed their gait the most during adaptation, reached their final adapted state more quickly, and had larger after-effects when the split-belt perturbation was removed. We also found that subjects who experienced larger disruptions of propulsion forces in early adaptation exhibited greater after-effects, which further highlights the catalytic role of propulsion forces on locomotor adaptation. The relevance of mechanical demands on shaping our movements was also indicated by the steady state split-belt behavior, during which each group recovered their baseline leg orientation to meet leg-specific force demands at the expense of step length symmetry. Notably, the flat group was nearly symmetric, whereas the incline and decline group overshot and undershot step length symmetry, respectively. Taken together, our results indicate that forces propelling the body facilitate gait changes during and after split-belt walking. Therefore, the particular propulsion demands to walk on a split-belt treadmill might explain the gait symmetry improvements in hemiparetic gait following split-belt training.

Background: Anklebot therapy has proven to be effective in improving hemiparetic gait. However, neither ankle torque steadiness nor the relationship between changes in force control and functional ...

Hemiparesis is one of the most frequent deficits after stroke. It is accompanied by an abnormal muscle co-contraction pattern and an altered force production that significantly contribute to reduced gait performance. These alterations lead to a reorganization of muscle coordination patterns to ensure stability and adjust the propulsion of the center of mass during walking. However, less is known about muscle actions in the paretic and non-paretic lower limbs during walking. In addition, co-contraction patterns were evaluated from only EMG data in post-stroke patients. Furthermore, post-stroke patients manifest higher levels of fatigability than healthy individuals. While several factors are involved in fatigue, the role of co-contraction remains poorly understood. The main objective of this thesis was to characterize the alterations of the muscle strategies of the lower limbs in post-stroke hemiparetic patients during walking and during fatigue induced by isokinetic concentric maximal contractions. This thesis introduces the novel use of an EMG-driven modelling approach to measure muscle forces generated around the knee and ankle joints of the paretic and non-paretic lower limbs during gait in post-stroke patients. In addition, we have shown that quantification of co-contraction from muscle moments is preferable compared to EMG measurements. The results showed that the reduced forces exerted by the plantar-flexors and the knee-extensors on the paretic side, gives a possible explanation for hemiparetic gait abnormalities. Increased forces generated by the knee-flexor and knee-extensor muscles on the non-paretic side, as well as increased force generated by the knee flexors on the paretic side, compared to healthy subjects, during the stance phase would be a behavioral reorganization to better support body weight and properly adjust the forward center of mass. This reorganization of muscle coordination patterns is also reflected by the increased levels of co-contraction (based on muscle moments) observed on the paretic and non-paretic side during walking. This seems to be an adaptive, compensatory strategy to ensure postural stability. However, increased co-contraction during walking can contribute to an increased energy cost in patients and lead to a more rapid fatigue development. The study of neuromuscular fatigue in post-stroke patients showed less fatigability compared to healthy subjects, in the presence of a higher level of co-contraction (based on EMG data). Decreasing agonist EMG during repeated concetric contractions, occurred in parallel with decreasing antagonist EMG, reducing the relative opposing force and resulting in a less decline in net torque. This seems to be a potential mechanism by which net torque output is preserved in post-stroke patients who are inherently weaker. The results of these studies underline the importance of developing rehabilitation programs focused on the strengthening of plantar flexors and knee extensors and on the selectivity of movement control, such as power training.; L'hémiparésie est une des déficiences fréquemment observée après un accident vasculaire cérébral (AVC). Elle s’accompagne d’une gestion anormale de la co-contraction musculaire et des déficits de production de force qui contribuent de manière significative à réduire la performance de la marche. Une réorganisation des stratégies musculaires est mise en place pour répondre aux contraintes de stabilité et de propulsion du centre de masse au cours de la marche. Cependant, la littérature reporte très peu de données sur les actions musculaires des membres, parétique et non-parétique, au cours de la marche. De plus, les patterns de co-contraction ont été évalués à partir des seules données EMG chez les patients post-AVC. Par ailleurs, les patients post-AVC présentent une fatigabilité plus importante que les individus sains. Alors que plusieurs facteurs sont impliqués dans la fatigue, le rôle de la co-contraction reste mal connu. L’objectif principal de ce travail était de caractériser les altérations des stratégies musculaires des membres inférieurs chez des patients hémiparétiques post-AVC au cours de la marche et lors de la fatigue induite par des contractions maximales volontaires concentriques isocinétiques. Ce travail introduit l'utilisation novatrice d'une modélisation neuromusculo-squelettique assistée par EMG pour estimer les forces musculaires générées autour des articulations du genou et de la cheville au cours de la marche chez des patients post-AVC. De plus, nous avons montré qu’une quantification de la co-contraction à partir des moments musculaires est préférable par rapport à des mesures EMG. Les résultats ont montré que les forces réduites développées par les fléchisseurs plantaires de la cheville et les extenseurs du genou du côté parétique seraient à l’origine des troubles de la marche hémiparétique. Les forces musculaires élevées produites par les quadriceps et les fléchisseurs du genou du côté nonparétique, ainsi que la force élevée générée par les fléchisseurs du genou du côté parétique, par rapport aux sujets sains, pendant la phase d’appui correspondrait à une réorganisation comportementale, permettant d’augmenter la stabilité et d’ajuster la propulsion du centre de masse. Cette réorganisation des patterns de coordination musculaire se manifeste également par des niveaux élevés de co-contraction (basée sur les moments musculaires) observés du côté parétique et non-parétique au cours de la marche. Il s’agit d’une stratégie d'adaptation permettant d’améliorer la stabilité articulaire. Cependant, la cocontraction plus élevée au cours de la marche peut contribuer à l’augmentation du coût énergétique chez les patients et entraîner une fatigue plus rapide. L’étude de la fatigue neuromusculaire chez les patients post-AVC a mis en évidence une fatigabilité moindre par rapport aux sujets sains en présence d’un niveau plus élevé de co-contraction (basée sur les données EMG). Le déclin de l’activité EMG agoniste lors de contractions concentriques répétées, s’est produit parallèlement à un déclin de l’activité EMG antagoniste diminuant la force d’opposition au mouvement et entraînant une moindre diminution du moment net. Ceci semble être un mécanisme potentiel par lequel la production du moment net est préservée chez les patients post-AVC qui sont intrinsèquement plus faibles. Les résultats de ce travail soulignent l’importance de développer des programmes de rééducation centrés sur le renforcement des fléchisseurs plantaires et des extenseurs du genou et sur la sélectivité du contrôle des mouvements tel que l’entraînement en puissance.

Hemiparesis is one of the most frequent deficits after stroke. It is accompanied by an abnormal muscle co-contraction pattern and an altered force production that significantly contribute to reduced gait performance. These alterations lead to a reorganization of muscle coordination patterns to ensure stability and adjust the propulsion of the center of mass during walking. However, less is known about muscle actions in the paretic and non-paretic lower limbs during walking. In addition, co-contraction patterns were evaluated from only EMG data in post-stroke patients. Furthermore, post-stroke patients manifest higher levels of fatigability than healthy individuals. While several factors are involved in fatigue, the role of co-contraction remains poorly understood. The main objective of this thesis was to characterize the alterations of the muscle strategies of the lower limbs in post-stroke hemiparetic patients during walking and during fatigue induced by isokinetic concentric maximal contractions. This thesis introduces the novel use of an EMG-driven modelling approach to measure muscle forces generated around the knee and ankle joints of the paretic and non-paretic lower limbs during gait in post-stroke patients. In addition, we have shown that quantification of co-contraction from muscle moments is preferable compared to EMG measurements. The results showed that the reduced forces exerted by the plantar-flexors and the knee-extensors on the paretic side, gives a possible explanation for hemiparetic gait abnormalities. Increased forces generated by the knee-flexor and knee-extensor muscles on the non-paretic side, as well as increased force generated by the knee flexors on the paretic side, compared to healthy subjects, during the stance phase would be a behavioral reorganization to better support body weight and properly adjust the forward center of mass. This reorganization of muscle coordination patterns is also reflected by the increased levels of co-contraction (based on muscle moments) observed on the paretic and non-paretic side during walking. This seems to be an adaptive, compensatory strategy to ensure postural stability. However, increased co-contraction during walking can contribute to an increased energy cost in patients and lead to a more rapid fatigue development. The study of neuromuscular fatigue in post-stroke patients showed less fatigability compared to healthy subjects, in the presence of a higher level of co-contraction (based on EMG data). Decreasing agonist EMG during repeated concetric contractions, occurred in parallel with decreasing antagonist EMG, reducing the relative opposing force and resulting in a less decline in net torque. This seems to be a potential mechanism by which net torque output is preserved in post-stroke patients who are inherently weaker. The results of these studies underline the importance of developing rehabilitation programs focused on the strengthening of plantar flexors and knee extensors and on the selectivity of movement control, such as power training.; L'hémiparésie est une des déficiences fréquemment observée après un accident vasculaire cérébral (AVC). Elle s’accompagne d’une gestion anormale de la co-contraction musculaire et des déficits de production de force qui contribuent de manière significative à réduire la performance de la marche. Une réorganisation des stratégies musculaires est mise en place pour répondre aux contraintes de stabilité et de propulsion du centre de masse au cours de la marche. Cependant, la littérature reporte très peu de données sur les actions musculaires des membres, parétique et non-parétique, au cours de la marche. De plus, les patterns de co-contraction ont été évalués à partir des seules données EMG chez les patients post-AVC. Par ailleurs, les patients post-AVC présentent une fatigabilité plus importante que les individus sains. Alors que plusieurs facteurs sont impliqués dans la fatigue, le rôle de la co-contraction reste mal connu. L’objectif principal de ce travail était de caractériser les altérations des stratégies musculaires des membres inférieurs chez des patients hémiparétiques post-AVC au cours de la marche et lors de la fatigue induite par des contractions maximales volontaires concentriques isocinétiques. Ce travail introduit l'utilisation novatrice d'une modélisation neuromusculo-squelettique assistée par EMG pour estimer les forces musculaires générées autour des articulations du genou et de la cheville au cours de la marche chez des patients post-AVC. De plus, nous avons montré qu’une quantification de la co-contraction à partir des moments musculaires est préférable par rapport à des mesures EMG. Les résultats ont montré que les forces réduites développées par les fléchisseurs plantaires de la cheville et les extenseurs du genou du côté parétique seraient à l’origine des troubles de la marche hémiparétique. Les forces musculaires élevées produites par les quadriceps et les fléchisseurs du genou du côté nonparétique, ainsi que la force élevée générée par les fléchisseurs du genou du côté parétique, par rapport aux sujets sains, pendant la phase d’appui correspondrait à une réorganisation comportementale, permettant d’augmenter la stabilité et d’ajuster la propulsion du centre de masse. Cette réorganisation des patterns de coordination musculaire se manifeste également par des niveaux élevés de co-contraction (basée sur les moments musculaires) observés du côté parétique et non-parétique au cours de la marche. Il s’agit d’une stratégie d'adaptation permettant d’améliorer la stabilité articulaire. Cependant, la cocontraction plus élevée au cours de la marche peut contribuer à l’augmentation du coût énergétique chez les patients et entraîner une fatigue plus rapide. L’étude de la fatigue neuromusculaire chez les patients post-AVC a mis en évidence une fatigabilité moindre par rapport aux sujets sains en présence d’un niveau plus élevé de co-contraction (basée sur les données EMG). Le déclin de l’activité EMG agoniste lors de contractions concentriques répétées, s’est produit parallèlement à un déclin de l’activité EMG antagoniste diminuant la force d’opposition au mouvement et entraînant une moindre diminution du moment net. Ceci semble être un mécanisme potentiel par lequel la production du moment net est préservée chez les patients post-AVC qui sont intrinsèquement plus faibles. Les résultats de ce travail soulignent l’importance de développer des programmes de rééducation centrés sur le renforcement des fléchisseurs plantaires et des extenseurs du genou et sur la sélectivité du contrôle des mouvements tel que l’entraînement en puissance.

Gait is the collective term for the two types of bipedal locomotion, walking and running. This paper is focused on walking. The analysis of human gait is of interest to many different disciplines, including biomechanics, human-movement science, rehabilitation and medicine in general. Here we present a new model that is capable of reproducing the properties of walking, normal and pathological. The aim of this paper is to establish the biomechanical principles that underlie human walking by using Lagrange method. The constraint forces of Rayleigh dissipation function, through which to consider the effect on the tissues in the gait, are included. Depending on the value of the factor present in the Rayleigh dissipation function, both normal and pathological gait can be simulated. First of all, we apply it in the normal gait and then in the permanent hemiparetic gait. Anthropometric data of adult person are used by simulation, and it is possible to use anthropometric data for children but is necessary to consider existing table of anthropometric data. Validation of these models includes simulations of passive dynamic gait that walk on level ground. The dynamic walking approach provides a new perspective of gait analysis, focusing on the kinematics and kinetics of gait. There have been studies and simulations to show normal human gait, but few of them have focused on abnormal, especially hemiparetic gait. Quantitative comparisons of the model predictions with gait measurements show that the model can reproduce the significant characteristics of normal gait.

Hemiparetic gait is characterised by temporal asymmetry and variability, and these variables are improved by auditory cueing. Stepping in place incorporates aspects of gait and may be a useful tool for locomotor training. The aim of this pilot study was to investigate the use of a single-tone and dual-tone metronome to cue stepping in place after hemiparetic stroke. Eight participants completed an uncued baseline stepping condition and two cued stepping conditions utilising a single-tone and a dual-tone metronome. Step times were determined from force plate data, and asymmetry and variability were calculated for the three conditions. Step time asymmetry was significantly reduced in the single-tone condition compared to baseline, and paretic step time variability was significantly reduced in both cued conditions. The single-tone metronome appeared to be preferred to the dual-tone metronome based on participant feedback. The results of this pilot study suggest that metronome cueing produces similar benefits on stepping in place to previously reported findings in walking. Further research on whether stepping in place to a metronome can be used for locomotor training is needed.

Mechanical properties of an articulated ankle-foot orthosis (AFO) are closely related to gait performance in individuals post-stroke. This paper presents a pilot study on the mechanical properties of a novel articulated AFO with adjustable plantarflexion resistance, dorsiflexion resistance and alignment, and its effect on ankle and knee joint kinematics and kinetics in an individual post-stroke during gait. The mechanical properties of the AFO were quantified. Gait analysis was performed using a 3D motion capture system with a split-belt instrumented treadmill under 12 different settings of the mechanical properties of the AFO [i.e. 4 plantarflexion resistances (P1