scholarly journals Effects of targeted assistance and perturbations on the relationship between pelvis motion and step width in people with chronic stroke

2020 ◽  
Author(s):  
Nicholas K. Reimold ◽  
Holly A. Knapp ◽  
Alyssa N. Chesnutt ◽  
Alexa Agne ◽  
Jesse C. Dean
Keyword(s):  
Force Field ◽  
Chronic Stroke ◽  
Step Width ◽  
Foot Placement ◽  
After Effects ◽  
Minute Period ◽  
After Effect ◽  
Targeted Assistance ◽  
Future Work ◽  
The Relationship

AbstractBackgroundPeople with chronic stroke (PwCS) often exhibit a weakened relationship between pelvis motion and paretic step width, a behavior important for gait stabilization. We have developed a force-field able to manipulate this relationship on a step-by-step basis.ObjectiveThe objective of this study was to investigate the effects of a single exposure to our novel force-field on the step-by-step modulation of paretic step width among PwCS, quantified by the partial correlation between mediolateral pelvis displacement at the start of a step and paretic step width (step start paretic ρdisp).MethodsFollowing a 3-minute period of normal walking, participants were exposed to 5-minutes of either force-field assistance (n=10; pushing the swing leg toward a mechanically-appropriate step width) or perturbations (n=10; pushing the swing leg away from a mechanically-appropriate step width). This period of assistance or perturbations was followed by a 1-minute catch period to identify any after-effects, a sign of sensorimotor adaptation.ResultsWe found that assistance did not have a significant direct effect or after-effect on step start paretic ρdisp. In contrast, perturbations directly reduced step start paretic ρdisp (p=0.004), but were followed by an after-effect in which this metric was increased above the baseline level (p=0.02).ConclusionsThese initial results suggest that PwCS have the ability to strengthen the link between pelvis motion and paretic foot placement if exposed to a novel mechanical environment, which may benefit gait stability. Future work is needed to determine whether this effect can be extended with repeated exposure to force-field perturbations.

scholarly journals Altered active control of step width in response to mediolateral leg perturbations while walking

2019 ◽  
Author(s):  
Nicholas K. Reimold ◽  
Holly A. Knapp ◽  
Rachel E. Henderson ◽  
Landi Wilson ◽  
Alyssa N. Chesnutt ◽  
...  
Keyword(s):  
Force Field ◽  
Active Control ◽  
Repeated Exposure ◽  
Step Width ◽  
After Effects ◽  
Body Dynamics ◽  
Walking Balance ◽  
The Relationship ◽  
Minimal Evidence ◽  
Normal Relationship

AbstractDuring human walking, step width is predicted by mediolateral motion of the pelvis, a relationship that can be attributed to a combination of passive body dynamics and active sensorimotor control. The purpose of the present study was to investigate whether humans modulate the active control of step width in response to a novel mechanical environment. Participants were repeatedly exposed to a force-field that either assisted or perturbed the normal relationship between pelvis motion and step width, separated by washout periods to detect the presence of potential after-effects. As intended, force-field assistance directly strengthened the relationship between pelvis displacement and step width. This relationship remained strengthened with repeated exposure to assistance, and returned to baseline afterward, providing minimal evidence for assistance-driven changes in active control. In contrast, force-field perturbations directly weakened the relationship between pelvis motion and step width. Repeated exposure to perturbations diminished this negative direct effect, and produced larger positive after-effects once the perturbations ceased. Both of these results provide evidence of gradual changes in active control in response to perturbations. In the longer term, these methods may be useful for improving deficits in the active control of step width often observed among clinical populations with poor walking balance.

scholarly journals Application of a novel force-field to manipulate the relationship between pelvis motion and step width in human walking

2019 ◽  
Author(s):  
Lauren N. Heitkamp ◽  
Katy H. Stimpson ◽  
Jesse C. Dean
Keyword(s):  
Force Field ◽  
Clinical Intervention ◽  
Human Walking ◽  
Proof Of Concept ◽  
Step Width ◽  
Mode 2 ◽  
Partial Correlations ◽  
Neurological Injuries ◽  
The Relationship ◽  
Neurologically Intact

AbstractMotion of the pelvis throughout a step predicts step width during human walking. This behavior is often considered an important component of ensuring bipedal stability, but can be disrupted in populations with neurological injuries. The purpose of this study was to determine whether a novel force-field that exerts mediolateral forces on the legs can manipulate the relationship between pelvis motion and step width, providing proof-of-concept for a future clinical intervention. We designed a force-field able to: 1) minimize the delivered mediolateral forces (Transparent mode); 2) apply mediolateral forces to assist the leg toward mechanically-appropriate step widths (Assistive mode); and 3) apply mediolateral forces to perturb the leg away from mechanically-appropriate step widths (Perturbing mode). Neurologically-intact participants were randomly assigned to either the Assistive group (n=12) or Perturbing group (n=12), and performed a series of walking trials in which they interfaced with the force-field. We quantified the step-by-step relationship between mediolateral pelvis displacement and step width using partial correlations. Walking in the Transparent force-field had a minimal effect on this relationship. However, force-field assistance directly strengthened the relationship between pelvis displacement and step width, whereas force-field perturbations weakened this relationship. Both assistance and perturbations were followed by short-lived effects during a wash-out period, in which the relationship between pelvis displacement and step width differed from the baseline value. The present results demonstrate that the link between pelvis motion and step width can be manipulated through mechanical means, which may be useful for retraining gait balance in clinical populations.

The Relationship Between Spatiotemporal Gait Asymmetry and Balance in Individuals With Chronic Stroke

2014 ◽  
Vol 30 (1) ◽  
pp. 31-36 ◽  
Author(s):  
Michael D. Lewek ◽  
Claire E. Bradley ◽  
Clinton J. Wutzke ◽  
Steven M. Zinder
Keyword(s):  
Weight Distribution ◽  
Balance Control ◽  
Step Length ◽  
Chronic Stroke ◽  
Step Width ◽  
Time Asymmetry ◽  
Swing Time ◽  
Gait Asymmetry ◽  
Stance Time ◽  
The Relationship

Falls are common after stroke and often attributed to poor balance. Falls often occur during walking, suggesting that walking patterns may induce a loss of balance. Gait after stroke is frequently spatiotemporally asymmetric, which may decrease balance. The purpose of this study is to determine the relationship between spatiotemporal gait asymmetry and balance control. Thirty-nine individuals with chronic stroke walked at comfortable and fast speeds to calculate asymmetry ratios for step length, stance time, and swing time. Balance measures included the Berg Balance Scale, step width during gait, and the weight distribution between legs during standing. Correlational analyses determined the relationships between balance and gait asymmetry. At comfortable and fast gait speeds, step width was correlated with stance time and swing time asymmetries (r= 0.39−0.54). Berg scores were correlated with step length and swing time asymmetries (r= –0.36 to –0.63). During fast walking, the weight distribution between limbs was correlated with stance time asymmetry (r= –0.41). Spatiotemporal gait asymmetry was more closely related to balance measures involving dynamic tasks than static tasks, suggesting that gait asymmetry may be related to the high number of falls poststroke. Further study to determine if rehabilitation that improves gait asymmetry has a similar influence on balance is warranted.

Identifying Physico-Chemical Laws from the Robotically Collected Data

2019 ◽  
Author(s):  
Liwei Cao ◽  
Danilo Russo ◽  
Vassilios S. Vassiliadis ◽  
Alexei Lapkin
Keyword(s):  
Experimental Data ◽  
Numerical Models ◽  
Predictor Variable ◽  
Physical Models ◽  
Training Data ◽  
Mixed Integer ◽  
Physico Chemical ◽  
Data Points ◽  
Future Work ◽  
The Relationship

<p>A mixed-integer nonlinear programming (MINLP) formulation for symbolic regression was proposed to identify physical models from noisy experimental data. The formulation was tested using numerical models and was found to be more efficient than the previous literature example with respect to the number of predictor variables and training data points. The globally optimal search was extended to identify physical models and to cope with noise in the experimental data predictor variable. The methodology was coupled with the collection of experimental data in an automated fashion, and was proven to be successful in identifying the correct physical models describing the relationship between the shear stress and shear rate for both Newtonian and non-Newtonian fluids, and simple kinetic laws of reactions. Future work will focus on addressing the limitations of the formulation presented in this work, by extending it to be able to address larger complex physical models.</p><p><br></p>

Adolescent Language: Models, Assessment, and Links to Reading

2019 ◽  
Author(s):  
Amanda Goodwin ◽  
Yaacov Petscher ◽  
Jamie Tock
Keyword(s):  
Reading Comprehension ◽  
Bifactor Model ◽  
Language Models ◽  
Multiple Group ◽  
Global Factor ◽  
Eighth Grade Students ◽  
Key Aspects ◽  
Future Work ◽  
The Relationship ◽  
Best Fit

Various models have highlighted the complexity of language. Building on foundational ideas regarding three key aspects of language, our study contributes to the literature by 1) exploring broader conceptions of morphology, vocabulary, and syntax, 2) operationalizing this theoretical model into a gamified, standardized, computer-adaptive assessment of language for fifth to eighth grade students entitled Monster, PI, and 3) uncovering further evidence regarding the relationship between language and standardized reading comprehension via this assessment. Multiple-group item response theory (IRT) across grades show that morphology was best fit by a bifactor model of task specific factors along with a global factor related to each skill. Vocabulary was best fit by a bifactor model that identifies performance overall and on specific words. Syntax, though, was best fit by a unidimensional model. Next, Monster, PI produced reliable scores suggesting language can be assessed efficiently and precisely for students via this model. Lastly, performance on Monster, PI explained more than 50% of variance in standardized reading, suggesting operationalizing language via Monster, PI can provide meaningful understandings of the relationship between language and reading comprehension. Specifically, considering just a subset of a construct, like identification of units of meaning, explained significantly less variance in reading comprehension. This highlights the importance of considering these broader constructs. Implications indicate that future work should consider a model of language where component areas are considered broadly and contributions to reading comprehension are explored via general performance on components as well as skill level performance.

Potential Role of Inflammation in Associations between Particulate Matter and Heart Failure

2018 ◽  
Vol 24 (3) ◽  
pp. 341-358 ◽  
Author(s):  
Xiaotong Ji ◽  
Yingying Zhang ◽  
Guangke Li ◽  
Nan Sang
Keyword(s):  
Heart Failure ◽  
Particulate Matter ◽  
Inflammatory Response ◽  
Heart Diseases ◽  
Experimental Studies ◽  
Epidemiological Studies ◽  
Inflammatory Mechanism ◽  
High Concentrations ◽  
Future Work ◽  
The Relationship

Recently, numerous studies have found that particulate matter (PM) exposure is correlated with increased hospitalization and mortality from heart failure (HF). In addition to problems with circulation, HF patients often display high expression of cytokines in the failing heart. Thus, as a recurring heart problem, HF is thought to be a disorder characterized in part by the inflammatory response. In this review, we intend to discuss the relationship between PM exposure and HF that is based on inflammatory mechanism and to provide a comprehensive, updated evaluation of the related studies. Epidemiological studies on PM-induced heart diseases are focused on high concentrations of PM, high pollutant load exposure in winter, or susceptible groups with heart diseases, etc. Furthermore, it appears that the relationship between fine or ultrafine PM and HF is stronger than that between HF and coarse PM. However, fewer studies paid attention to PM components. As for experimental studies, it is worth noting that coarse PM may indirectly promote the inflammatory response in the heart through systematic circulation of cytokines produced primarily in the lungs, while ultrafine PM and its components can enter circulation and further induce inflammation directly in the heart. In terms of PM exposure and enhanced inflammation during the pathogenesis of HF, this article reviews the following mechanisms: hemodynamics, oxidative stress, Toll-like receptors (TLRs) and epigenetic regulation. However, many problems are still unsolved, and future work will be needed to clarify the complex biologic mechanisms and to identify the specific components of PM responsible for adverse effects on heart health.

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