194 research outputs found

    An Investigation of Kinetic Visual Biofeedback on Dynamic Stance Symmetry

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    The intent of the following research is to utilize task-specific, constraint-induced therapies and apply towards dynamic training for symmetrical balance. Modifications to an elliptical trainer were made to both measure weight distributions during dynamic stance as well as provide kinetic biofeedback through a man-machine interface. Following a review of the background, which includes research from several decades that are seminal to current studies, a design review is discussed to cover the design of the modified elliptical (Chapter 2). An initial study was conducted in a healthy sample population in order to determine the best visual biofeedback representation by comparing different man-machine interfaces (Chapter 3). Index of gait symmetry measures indicated that one display interface optimized participant performance during activity with the modified elliptical trainer. A second study was designed to determine the effects of manipulating the gain of the signal to encourage increased distribution towards the non-dominant weight bearing limb. The purpose of the second study was to better understand the threshold value of gain manipulation in a healthy sample set. Results analyzing percentage error as a measure of performance show that a range between 5-10% allows for a suitable threshold value to be applied for participants who have suffered a stroke. A final study was conducted to apply results/knowledge from the previous two studies to a stroke cohort to determine short-term carryover following training with the modified elliptical trainer. Data taken from force measurements on the elliptical trainer suggest that there was carryover with decreased error from pre to post training. For one participant GaitRite® data show a significant difference from pre to post measurements in single limb support. The results of the research suggest that visual biofeedback can improve symmetrical performance during dynamic patterns. For a better understanding of visual biofeedback delivery, one display representation proved to be beneficial compared to the others which resulted in improved performance. Results show that healthy human participants can minimize error with visual biofeedback and continue minimizing error until a threshold value of 10%. Finally, results have shown promise towards applying such a system for kinetic gait rehabilitation

    Using Swing Resistance and Assistance to Improve Gait Symmetry in Individuals Post-Stroke

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    A major characteristic of hemiplegic gait observed in individuals post-stroke is spatial and temporal asymmetry, which may increase energy expenditure and the risk of falls. The purpose of this study was to examine the effects of swing resistance/assistance applied to the affected leg on gait symmetry in individuals post-stroke. We recruited 10 subjects with chronic stroke who demonstrated a shorter step length with their affected leg in comparison to the non-affected leg during walking. They participated in two test sessions for swing resistance and swing assistance, respectively. During the adaptation period, subjects counteracted the step length deviation caused by the applied swing resistance force, resulting in an aftereffect consisting of improved step length symmetry during the post-adaptation period. In contrast, subjects did not counteract step length deviation caused by swing assistance during adaptation period and produced no aftereffect during the post-adaptation period. Locomotor training with swing resistance applied to the affected leg may improve step length symmetry through error-based learning. Swing assistance reduces errors in step length during stepping; however, it is unclear whether this approach would improve step length symmetry. Results from this study may be used to develop training paradigms for improving gait symmetry of stroke survivors

    Abnormal joint torque patterns exhibited by chronic stroke subjects while walking with a prescribed physiological gait pattern

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    <p>Abstract</p> <p>Background</p> <p>It is well documented that individuals with chronic stroke often exhibit considerable gait impairments that significantly impact their quality of life. While stroke subjects often walk asymmetrically, we sought to investigate whether prescribing near normal physiological gait patterns with the use of the Lokomat robotic gait-orthosis could help ameliorate asymmetries in gait, specifically, promote similar ankle, knee, and hip joint torques in both lower extremities. We hypothesized that hemiparetic stroke subjects would demonstrate significant differences in total joint torques in both the frontal and sagittal planes compared to non-disabled subjects despite walking under normal gait kinematic trajectories.</p> <p>Methods</p> <p>A motion analysis system was used to track the kinematic patterns of the pelvis and legs of 10 chronic hemiparetic stroke subjects and 5 age matched controls as they walked in the Lokomat. The subject's legs were attached to the Lokomat using instrumented shank and thigh cuffs while instrumented footlifters were applied to the impaired foot of stroke subjects to aid with foot clearance during swing. With minimal body-weight support, subjects walked at 2.5 km/hr on an instrumented treadmill capable of measuring ground reaction forces. Through a custom inverse dynamics model, the ankle, knee, and hip joint torques were calculated in both the frontal and sagittal planes. A single factor ANOVA was used to investigate differences in joint torques between control, unimpaired, and impaired legs at various points in the gait cycle.</p> <p>Results</p> <p>While the kinematic patterns of the stroke subjects were quite similar to those of the control subjects, the kinetic patterns were very different. During stance phase, the unimpaired limb of stroke subjects produced greater hip extension and knee flexion torques than the control group. At pre-swing, stroke subjects inappropriately extended their impaired knee, while during swing they tended to abduct their impaired leg, both being typical abnormal torque synergy patterns common to stroke gait.</p> <p>Conclusion</p> <p>Despite the Lokomat guiding stroke subjects through physiologically symmetric kinematic gait patterns, abnormal asymmetric joint torque patterns are still generated. These differences from the control group are characteristic of the hip hike and circumduction strategy employed by stroke subjects.</p

    Biomechanical mechanisms underlying exosuit-induced improvements in walking economy after stroke

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    Stroke-induced hemiparetic gait is characteristically asymmetric and metabolically expensive. Weakness and impaired control of the paretic ankle contribute to reduced forward propulsion and ground clearance—walking subtasks critical for safe and efficient locomotion. Targeted gait interventions that improve paretic ankle function after stroke are therefore warranted. We have developed textile-based, soft wearable robots that transmit mechanical power generated by off-board or body-worn actuators to the paretic ankle using Bowden cables (soft exosuits) and have demonstrated the exosuits can overcome deficits in paretic limb forward propulsion and ground clearance, ultimately reducing the metabolic cost of hemiparetic walking. This study elucidates the biomechanical mechanisms underlying exosuit-induced reductions in metabolic power. We evaluated the relationships between exosuit-induced changes in the body center of mass (COM) power generated by each limb, individual joint powers, and metabolic power. Compared to walking with an exosuit unpowered, exosuit assistance produced more symmetrical COM power generation during the critical period of the step-to-step transition (22.4±6.4% more symmetric). Changes in individual limb COM power were related to changes in paretic (R2= 0.83, P= 0.004) and nonparetic (R2= 0.73, P= 0.014) ankle power. Interestingly, despite the exosuit providing direct assistance to only the paretic limb, changes in metabolic power were related to changes in nonparetic limb COM power (R2= 0.80, P= 0.007), not paretic limb COM power (P> 0.05). These findings provide a fundamental understanding of how individuals poststroke interact with an exosuit to reduce the metabolic cost of hemiparetic walking.Accepted manuscript2019-03-0

    Effects of intense and unpredictable perturbations during gait training in individuals with hemiparesis due to cerebrovascular accident at the chronic phase

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    In individuals with hemiparesis following a cerebrovascular accident (CVA) at the chronic phase, the deficits of balance during gait are common due to the impairment of the reactive and anticipatory postural responses. However, traditional interventions based on voluntary movements do not target the improvement of these responses for the improvement of dynamic balance. Studies involving the applications of unpredictable gait perturbations reported limited improvements in balance and gait abilities in this population. Furthermore, due to the concomitant use of other interventions or the absence of a control group in these studies, the attribution of the reported changes of these studies specifically to unpredictable gait perturbations is not possible. On the other hand, our knowledge about the underlying mechanisms of improvement of dynamic balance in individuals at the chronic phase post-stroke is limited. Thus, the main objectives of this thesis were: 1) to compare the effects of intense and unpredictable gait perturbations on balance and gait abilities with a control intervention including walking-only on a split-belt treadmill; and 2) to compare biomechanical determinants of dynamic balance between a group of healthy participants (n=15) and two groups of hemiparetic participants following CVA at the chronic phase [stroke-fast group (overground gait speed ≥ 1 m/s, n=20) and stroke-slow group (overground gait speed < 1 m/s, n=18)], as well as between stroke groups. To achieve the first objective, 18 participants were recruited and assigned through covariate adaptive randomization to the experimental group (n=10) or the comparison group (n=8) in a randomized controlled pilot trial. The participants in the comparison group walked merely on the treadmill. Both groups received nine training sessions over three weeks. Improvement of dynamic balance (assessed by the MiniBESTest) was the only statistically significant difference observed between the experimental and comparison groups. To reach the second objective, the biomechanical determinants of dynamic balance were compared at six time points of the gait cycle between the healthy group, stroke-fast group and stroke-slow group. The biomechanical determinants were the length and width of the base of support (BOS) in addition to the relative positions of the center of pressure (COP), the center of mass (COM) and the extrapolated COM (XCOM) along the anteroposterior and lateral axes of the BOS. The results indicate that participants with hemiparesis due to CVA at the chronic phase showed altered biomechanical variables compared to healthy participants, particularly at the single support phase of gait, suggesting a strategy to maintain their dynamic balance. Altogether, the findings suggest that the experimental intervention improved dynamic balance during gait probably through the normalization of its biomechanical determinants in individuals in the chronic phase post-stroke.Chez des personnes présentant une hémiparésie à la suite d’un accident vasculaire cérébral (AVC), les carences de l'équilibre dynamique pendant la marche sont fréquentes en raison de l'altération des réponses posturales réactives et anticipées. Toutefois, les interventions traditionnelles basées sur la réalisation de mouvements volontaires ne visent pas l'amélioration de ces réponses qui sous-tendent l'amélioration de l'équilibre dynamique. Des études portant sur l’application spécifique de perturbations imprévisibles de la marche ont rapporté des améliorations limitées des capacités de marche et d'équilibre chez cette population. Par ailleurs, en raison de l'utilisation concomitante d’autres interventions ou de l'absence d'un groupe témoin dans ces études, il n'est pas possible d'attribuer les changements rapportés spécifiquement aux perturbations imprévisibles de la marche. D'un autre côté, nos connaissances sur les mécanismes sous-jacents à l'amélioration de l'équilibre dynamique chez les individus ayant subi un AVC en phase chronique sont peu développées. Les principaux objectifs de cette thèse sont donc : 1) de comparer les effets de perturbations intenses et imprévisibles de la marche sur l'équilibre et les capacités de marche avec une intervention contrôle incluant uniquement de la marche sur un tapis roulant à double courroie ; et 2) de comparer les déterminants biomécaniques de l'équilibre dynamique entre un groupe de participants sains (n=15) et deux groupes de participants présentant une hémiparésie en phase chronique à la suite d’un AVC [les groupes AVC rapide (vitesse au sol ≥ 1 m/s, n=20) et AVC lent (vitesse au sol < 1 m/s, n=18)] ainsi qu’entre les groupes d'AVC. Pour atteindre le premier objectif, 18 participants ont été recrutés et assignés par randomisation avec équilibre des co-variables (“covariate adaptive randomization”) au groupe expérimental (n=10) ou au groupe de comparaison (n=8) dans un essai pilote contrôlé randomisé. Les participants du groupe de comparaison marchait simplement sur un tapis roulant. Les deux groupes ont reçu neuf sessions d’entraînement réparties sur trois semaines. L'amélioration de l'équilibre dynamique (évaluée par le biais du MiniBESTest) était la seule différence statistiquement significative observée entre le groupe expérimental et le groupe de comparaison à la suite de l’intervention. Pour atteindre le deuxième objectif, les déterminants biomécaniques de l'équilibre dynamique ont été comparés à six moments du cycle de marche entre le groupe sain, le groupe AVC rapide et le groupe AVC lent. Les déterminants biomécaniques étaient la longueur et la largeur de la base de support (BOS), en plus des positions relatives du centre de pression (COP), du centre de masse (COM) et du COM extrapolé (XCOM) dans les axes antéropostérieur et latéral de la BOS. Les résultats indiquent que les participants présentant une hémiparésie à la suite d’un AVC en phase chronique présentent des variables biomécaniques altérées par rapport aux participants sains, surtout lors de la phase d’appui unipodal, suggérant une stratégie pour maintenir leur équilibre dynamique. Dans l'ensemble, les résultats suggèrent que l’intervention expérimentale a amélioré l'équilibre dynamique pendant la marche, probablement en raison de la normalisation de ses déterminants biomécaniques chez les individus ayant subi un AVC en phase chronique

    Quantitative Assessment of Gait During Rehabilitation Using an Instrumented Treadmill

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    Kinetic gait analysis of subacute stroke is a relatively unexplored area of study. Chronic stroke literature on the subject is extensive but does not capture the time period where the extent of recovery is greatest. Translating methods of gait analysis seen in research to a clinical setting is subject to many additional requirements which have previously prevented such investigations. The work presented in this thesis represents the first investigation using NeuroRecoVR, a new instrumented treadmill facility located within an inpatient rehabilitation gym. Working directly with inpatient physiotherapists, this study examines kinetic based gait parameters to quantify levels of impairment in subacute stroke. Recovery is most readily seen in changes in the walking speed of an individual, with many other gait parameters changing alongside walking speed. Therefor the relationships for all parameters of interest to walking speed are investigated in both neurologically intact controls (n = 14) and those undergoing rehabilitation for subacute stroke (n = 15). Parameters including spatiotemporal measures, forces, impulses, center of mass trajectory, center of pressure variability, and measures of symmetry were calculated for both groups. Subacute stroke participants have higher levels of asymmetry, increased instability, and altered gait dynamics compared to neurologically intact controls. The extent of recovery for each parameter was examined in a subset of stroke patients who took part in instrumented treadmill training over 1-2 months of rehabilitation (n = 4; mean ±SD age = 65 ±17; mean ±SD days post stroke at first session = 79 ±67). These participants showed improvements in stability, walking speed, and symmetry over the course of rehabilitation. These results show the benefit and potential for the use of kinetic analysis for aspects of both research and rehabilitatio

    The role of movement errors in modifying spatiotemporal asymmetry post-stroke: a randomized clinical trial

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    Objective: Current rehabilitation to improve gait symmetry following stroke is based on one of two competing motor learning strategies: minimizing or augmenting symmetry errors. We sought to determine which of those motor learning strategies best improves overground spatiotemporal gait symmetry. Design: Randomized controlled trial. Setting: Rehabilitation research lab. Subjects: In all, 47 participants (59 ± 12 years old) with chronic hemiparesis post stroke and spatiotemporal gait asymmetry were randomized to error augmentation, error minimization, or conventional treadmill training (control) groups. Interventions: To augment or minimize asymmetry on a step-by-step basis, we developed a responsive, “closed-loop” control system, using a split-belt instrumented treadmill that continuously adjusted the difference in belt speeds to be proportional to the patient’s current asymmetry. Main measures: Overground spatiotemporal asymmetries and gait speeds were collected prior to and following 18 training sessions. Results: Step length asymmetry reduced after training, but stance time did not. There was no group × time interaction. Gait speed improved after training, but was not affected by type of asymmetry, or group. Of those who trained to modify step length asymmetry, there was a moderately strong linear relationship between the change in step length asymmetry and the change in gait speed. Conclusion: Augmenting errors was not superior to minimizing errors or providing only verbal feedback during conventional treadmill walking. Therefore, the use of verbal feedback to target spatiotemporal asymmetry, which was common to all participants, appears to be sufficient to reduce step length asymmetry. Alterations in stance time asymmetry were not elicited in any group

    Dynamic balance control during treadmill walking in chronic stroke survivors

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    Maintaining dynamic balance is an important component of walking function that is likely impaired in chronic stroke survivors, evidenced by an increased prevalence of falls. Dynamic balance control requires maintaining the center of mass (COM) within the base of support during movement. During walking, dynamic balance control is achieved largely by modifying foot placement to adjust the base of support. However, chronic stroke survivors have difficulty with both precision control of foot placement, as well as reduced control of COM movement. The objective of this dissertation was to characterize dynamic balance control strategies during walking in chronic stroke survivors. Additionally, we evaluated whether altered sensory feedback could be used to improve balance control in stroke survivors. Dynamic balance control was characterized during challenging walking conditions in stroke survivors and age-matched neurologically intact individuals. Adaptations to perturbations in frontal plane COM, induced using a custom cable-driven device, were used to further probe mechanisms of dynamic balance control. Despite larger amounts of COM movement and step widths, chronic stroke survivors produced a similar ratio of step width to COM sway, indicating that simply increasing step width does not produce a safer walking pattern for the stroke group. Placement of the paretic limb was unchanged in response to the external perturbations of trunk movement, which might underlie deficits in dynamic balance control. Augmented sensory feedback improved paretic foot placement and COM control, when applied during a stepping or treadmill walking task. These results provide insight into differences in dynamic balance control in stroke while also demonstrating that augmented sensory feedback signals might be used to improve balance control, and thus walking function for chronic stroke survivors

    Using Biofeedback to Reduce Spatiotemporal Asymmetry Impairs Dynamic Balance in People Post-Stroke

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    Background. People poststroke often walk with a spatiotemporally asymmetric gait, due in part to sensorimotor impairments in the paretic lower extremity. Although reducing asymmetry is a common objective of rehabilitation, the effects of improving symmetry on balance are yet to be determined. Objective. We established the concurrent validity of whole-body angular momentum as a measure of balance, and we determined if reducing step length asymmetry would improve balance by decreasing whole-body angular momentum. Methods. We performed clinical balance assessments and measured wholebody angular momentum during walking using a full-body marker set in a sample of 36 people with chronic stroke. We then used a biofeedback-based approach to modify step length asymmetry in a subset of 15 of these individuals who had marked asymmetry and we measured the resulting changes in whole-body angular momentum. Results. When participants walked without biofeedback, whole-body angular momentum in the sagittal and frontal plane was negatively correlated with scores on the Berg Balance Scale and Functional Gait Assessment supporting the validity of whole-body angular momentum as an objective measure of dynamic balance. We also observed that when participants walked more symmetrically, their wholebody angular momentum in the sagittal plane increased rather than decreased. Conclusions. Voluntary reductions of step length asymmetry in people poststroke resulted in reduced measures of dynamic balance. This is consistent with the idea that after stroke, individuals might have an implicit preference not to deviate from their natural asymmetry while walking because it could compromise their balance. Clinical Trials Number: NCT03916562

    New Trends in Neuromechanics and Motor Rehabilitation

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    Neuromechanics has been used to identify optimal rehabilitation protocols that successfully improve motor deficits in various populations, such as elderly people and individuals with neurological diseases (e.g., stroke, Parkinson’s disease, and essential tremor). By investigating structural and functional changes in the central and peripheral nervous systems based on neuromechanical theories and findings, we can expand our knowledge regarding underlying neurophysiological mechanisms and specific motor impairment patterns before and after therapies to further develop new training programs (e.g., non-invasive brain stimulation). Thus, the aim of this Special Issue is to present the main contributions of researchers and rehabilitation specialists in biomechanics, motor control, neurophysiology, neuroscience, and rehabilitation science. The current collection provides new neuromechanical approaches addressing theoretical, methodological, and practical topics for facilitating motor recovery progress
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