Dataset Information

Effects of Targeted Assistance and Perturbations on the Relationship Between Pelvis Motion and Step Width in People With Chronic Stroke.

ABSTRACT: During walking in neurologically-intact controls, larger mediolateral pelvis displacements or velocities away from the stance foot are accompanied by wider steps. This relationship contributes to gait stabilization, as modulating step width based on pelvis motion (hereby termed a "mechanically-appropriate" step width) reduces the risk of lateral losses of balance. The relationship between pelvis displacement and step width is often weakened among people with chronic stroke (PwCS) for steps with the paretic leg. Our objective was to investigate the effects of a single exposure to a novel force-field on the modulation of paretic step width. This modulation was quantified as the partial correlation between paretic step width and pelvis displacement at the step's start (step start paretic [Formula: see text]). Following 3-minutes of normal walking, participants were exposed to 5-minutes of either force-field assistance (n = 10; pushing the swing leg toward mechanically-appropriate step widths) or perturbations (n = 10: pushing the swing leg away from mechanically-appropriate step widths). This period of assistance or perturbations was followed by a 1-minute catch period to identify after-effects, a sign of altered sensorimotor control. The effects of assistance were equivocal, without a significant direct effect or after-effect on step start paretic [Formula: see text]. In contrast, perturbations directly reduced step start paretic [Formula: see text] (p = 0.004), but were followed by a positive after-effect (p = 0.02). These results suggest that PwCS can strengthen the link between pelvis motion and paretic step width if exposed to a novel mechanical environment. Future work is needed to determine whether this effect is extended with repeated perturbation exposure.

SUBMITTER: Reimold NK

PROVIDER: S-EPMC8844911 | biostudies-literature | 2021

REPOSITORIES: biostudies-literature

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Publications

Effects of Targeted Assistance and Perturbations on the Relationship Between Pelvis Motion and Step Width in People With Chronic Stroke.

Reimold Nicholas K NK Knapp Holly A HA Chesnutt Alyssa N AN Agne Alexa A Dean Jesse C JC

IEEE transactions on neural systems and rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society 20210226

During walking in neurologically-intact controls, larger mediolateral pelvis displacements or velocities away from the stance foot are accompanied by wider steps. This relationship contributes to gait stabilization, as modulating step width based on pelvis motion (hereby termed a "mechanically-appropriate" step width) reduces the risk of lateral losses of balance. The relationship between pelvis displacement and step width is often weakened among people with chronic stroke (PwCS) for steps with ...[more]

PMID: 33196440

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Project description:Many people with chronic stroke (PwCS) exhibit deficits in step width modulation, an important strategy for walking balance. A single exposure to swing leg perturbations can temporarily strengthen this modulation. The objective of this parallel, double-blinded, randomized controlled trial was to investigate whether repeated perturbations cause sustained increases in step modulation (NCT02964039; funded by the VA). 54 PwCS at the Medical University of South Carolina were randomly assigned to one of three intervention groups: Control (n = 18), with minimal forces; Assistive (n = 18), pushing the swing leg toward a mechanically appropriate location; Perturbing (n = 18), pushing the swing leg away from a mechanically appropriate location. All intervention groups included 24 training sessions over 12-weeks with up to 30-minutes of treadmill walking while interfaced with a novel force-field and a 12-week follow-up period, with five interspersed assessment sessions. Our primary outcome measure was paretic step width modulation, the partial correlation between step width and pelvis displacement (ρSW). Secondarily, we quantified swing and stance leg contributions to step modulation, clinical assessments of walking balance and confidence, and real-world falls. Outcomes were analyzed for participants who completed all assessment sessions (n = 44). Only the Perturbing group exhibited significant increases in paretic ρSW, which were present after 4-weeks of training and sustained through follow-up (t = 2.42-3.17). These changes were due to improved control of paretic swing leg positioning. However, perturbation-induced changes in step modulation were not always significantly greater than those in the Control group, and clinical assessments were similar across intervention groups. Participants in the Perturbing group experienced a lower fall rate than those in the Control group (incidence rate ratio = 0.53), although our small sample size warrants caution. The present results indicate that perturbations can cause sustained modifications of targeted biomechanical characteristics of post-stroke gait, although such changes alone may be insufficient to change more complex clinical assessments.

Project description:BackgroundIndividualized, targeted, and intense training is the hallmark of successful gait rehabilitation in people post-stroke. Specifically, increasing use of the impaired ankle to increase propulsion during the stance phase of gait has been linked to higher walking speeds and symmetry. Conventional progressive resistance training is one method used for individualized and intense rehabilitation, but often fails to target paretic ankle plantarflexion during walking. Wearable assistive robots have successfully assisted ankle-specific mechanisms to increase paretic propulsion in people post-stroke, suggesting their potential to provide targeted resistance to increase propulsion, but this application remains underexamined in this population. This work investigates the effects of targeted stance-phase plantarflexion resistance training with a soft ankle exosuit on propulsion mechanics in people post-stroke.MethodsWe conducted this study in nine individuals with chronic stroke and tested the effects of three resistive force magnitudes on peak paretic propulsion, ankle torque, and ankle power while participants walked on a treadmill at their comfortable walking speeds. For each force magnitude, participants walked for 1 min while the exosuit was inactive, 2 min with active resistance, and 1 min with the exosuit inactive, in sequence. We evaluated changes in gait biomechanics during the active resistance and post-resistance sections relative to the initial inactive section.ResultsWalking with active resistance increased paretic propulsion by more than the minimal detectable change of 0.8 %body weight at all tested force magnitudes, with an average increase of 1.29 ± 0.37 %body weight at the highest force magnitude. This improvement corresponded to changes of 0.13 ± 0.03 N m kg- 1 in peak biological ankle torque and 0.26 ± 0.04 W kg- 1 in peak biological ankle power. Upon removal of resistance, propulsion changes persisted for 30 seconds with an improvement of 1.49 ± 0.58 %body weight after the highest resistance level and without compensatory involvement of the unresisted joints or limb.ConclusionsTargeted exosuit-applied functional resistance of paretic ankle plantarflexors can elicit the latent propulsion reserve in people post-stroke. After-effects observed in propulsion highlight the potential for learning and restoration of propulsion mechanics. Thus, this exosuit-based resistive approach may offer new opportunities for individualized and progressive gait rehabilitation.

Project description:BackgroundMany people with chronic stroke (PwCS) exhibit walking balance deficits linked to increased fall risk and decreased balance confidence. One potential contributor to these balance deficits is a decreased ability to modulate mediolateral stepping behavior based on pelvis motion. This behavior, hereby termed mediolateral step modulation, is thought to be an important balance strategy but can be disrupted in PwCS.Research questionAre biomechanical metrics of mediolateral step modulation related to common clinical balance measures among PwCS?MethodsIn this cross-sectional study, 93 PwCS walked on a treadmill at their self-selected speed for 3-minutes. We quantified mediolateral step modulation for both paretic and non-paretic steps by calculating partial correlations between mediolateral pelvis displacement at the start of each step and step width (ρSW), mediolateral foot placement relative to the pelvis (ρFP), and final mediolateral location of the pelvis (ρPD) at the end of the step. We also assessed several common clinical balance measures (Functional Gait Assessment [FGA], Activities-specific Balance Confidence scale [ABC], self-reported fear of falling and fall history). We performed Spearman correlations to relate each biomechanical metric of step modulation to FGA and ABC scores. We performed Wilcoxon rank sum tests to compare each biomechanical metric between individuals with and without a fear of falling and a history of falls.ResultsOnly ρFP for paretic steps was significantly related to all four clinical balance measures; higher paretic ρFP values tended to be observed in participants with higher FGA scores, with higher ABC scores, without a fear of falling and without a history of falls. However, the strength of each of these relationships was only weak to moderate.SignificanceWhile the present results do not provide insight into causality, they justify future work investigating whether interventions designed to increase ρFP can improve clinical measures of post-stroke balance in parallel.

Dataset Information

Effects of Targeted Assistance and Perturbations on the Relationship Between Pelvis Motion and Step Width in People With Chronic Stroke.

Publications

Effects of Targeted Assistance and Perturbations on the Relationship Between Pelvis Motion and Step Width in People With Chronic Stroke.

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