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"Reactive stepping"

Stephen R Lord, Jacqueline C T Close
Falls pose a major threat to the well-being and quality of life of older people. Falls can result in fractures and other injuries, disability and fear and can trigger a decline in physical function and loss of autonomy. This article synthesises recent published findings on fall risk and mobility assessments and fall prevention interventions and considers how this field of research may evolve in the future. Fall risk topics include the utility of remote monitoring using wearable sensors and recent work investigating brain activation and gait adaptability...
April 25, 2018: Age and Ageing
St├ęphanie Essafi, Jeremy N Harvey
For condensed-phase reactions, commonly used kinetic models assume that energy exchange from and to solvent molecules is much faster than any reactive steps. However, it is becoming increasingly evident that this does not always hold true. In this work, we use molecular dynamics simulations to explore the time scale for energy transfer between solvent and solute in some typical organic solvents. As a reference, energy transfer between solvent molecules is also considered. The time scale is found to depend most strongly on the identity of the solvent...
April 12, 2018: Journal of Physical Chemistry. A
Digna de Kam, Jolanda M B Roelofs, Alexander C H Geurts, Vivian Weerdesteyn
OBJECTIVE: To determine the predictive value of leg and trunk inclination angles at stepping-foot contact for the capacity to recover from a backward balance perturbation with a single step in people after stroke. METHODS: Twenty-four chronic stroke survivors and 21 healthy controls were included in a cross-sectional study. We studied reactive stepping responses by subjecting participants to multidirectional stance perturbations at different intensities on a translating platform...
2018: PloS One
Justine Magnard, Christophe Cornu, Gilles Berrut, Thibault Deschamps
Inhibition is known to influence balance, step initiation and gait control. A specific subcomponent of inhibition, the perceptual inhibition process, has been suggested to be specifically involved in the integration of proprioceptive information that is necessary for efficient postural responses. This study aimed to investigate the inhibition requirements of planning and executing a choice step initiation task in young adults following experimental perturbation of proprioceptive information using Achilles tendon vibrations...
December 2017: Human Movement Science
Zhen Liu, Chandan Patel, Jeremy N Harvey, Raghavan B Sunoj
A systematic density functional theory exploration of various reactive steps together with benchmark coupled cluster results are used to propose an accurate model of the mechanism of the Morita-Baylis-Hillman (MBH) reaction in organic chemistry. This reaction has attracted considerable interest from the synthetic and mechanistic points of view in recent years, with both computational and experimental mechanistic studies. It has recently (R. E. Plata and D. A. Singleton, J. Am. Chem. Soc., 2015, 137, 3811-3826) been correctly pointed out that previous computational studies failed to reproduce known mechanistic features of the reaction...
November 22, 2017: Physical Chemistry Chemical Physics: PCCP
Patrick H Bunton, Michael P Tullier, Eckart Meiburg, John A Pojman
Viscous fingering can occur in fluid motion whenever a high mobility fluid displaces a low mobility fluid in a Darcy type flow. When the mobility difference is primarily attributable to viscosity (e.g., flow between the two horizontal plates of a Hele-Shaw cell), viscous fingering (VF) occurs, which is sometimes termed the Saffman-Taylor instability. Alternatively, in the presence of differences in density in a gravity field, buoyancy-driven convection can occur. These instabilities have been studied for decades, in part because of their many applications in pollutant dispersal, ocean currents, enhanced petroleum recovery, and so on...
October 2017: Chaos
Vicki L Gray, Chieh-Ling Yang, Sandy McCombe Waller, Mark W Rogers
BACKGROUND AND PURPOSE: Falls commonly occur as weight is transferred laterally, and impaired reactive stepping responses are associated with falls after stroke. The purpose of this study was to examine differences in and the determinants of mediolateral (M-L) protective stepping strategies when pulled off balance toward the paretic and nonparetic sides. METHODS: Eighteen individuals more than 6 months poststroke were pulled in the M-L direction by a lateral waist-pull perturbation system...
October 2017: Journal of Neurologic Physical Therapy: JNPT
Digna de Kam, Jolanda M B Roelofs, Amber K B D Bruijnes, Alexander C H Geurts, Vivian Weerdesteyn
BACKGROUND AND OBJECTIVE: Postural muscle responses are often impaired after stroke. We aimed to identify the contribution of deficits in very early postural responses to poorer reactive balance capacity, with a particular focus on reactive stepping as a key strategy for avoiding falls. METHODS: A total of 34 chronic stroke survivors and 17 controls were subjected to translational balance perturbations in 4 directions. We identified the highest perturbation intensity that could be recovered without stepping (single stepping threshold [SST]) and with maximally 1 step (multiple stepping threshold [MST])...
August 2017: Neurorehabilitation and Neural Repair
Alexander J Hunt, Brooke M Odle, Lisa M Lombardo, Musa L Audu, Ronald J Triolo
BACKGROUND: Implanted motor system neuroprostheses can be effective at increasing personal mobility of persons paralyzed by spinal cord injuries. However, currently available neural stimulation systems for standing employ patterns of constant activation and are unreactive to changing postural demands. METHODS: In this work, we developed a closed-loop controller for detecting forward-directed body disturbances and initiating a stabilizing step in a person with spinal cord injury...
June 10, 2017: Journal of Neuroengineering and Rehabilitation
Ki Seok Kim, Ki Hyun Kim, Yeonsig Nam, Jaeho Jeon, Soonmin Yim, Eric Singh, Jin Yong Lee, Sung Joo Lee, Yeon Sik Jung, Geun Young Yeom, Dong Woo Kim
Among the layered transition metal dichalcogenides (TMDs) that can form stable two-dimensional crystal structures, molybdenum disulfide (MoS2) has been intensively investigated because of its unique properties in various electronic and optoelectronic applications with different band gap energies from 1.29 to 1.9 eV as the number of layers decreases. To control the MoS2 layers, atomic layer etching (ALE) (which is a cyclic etching consisting of a radical-adsorption step such as Cl adsorption and a reacted-compound-desorption step via a low-energy Ar(+)-ion exposure) can be a highly effective technique to avoid inducing damage and contamination that occur during the reactive steps...
April 5, 2017: ACS Applied Materials & Interfaces
Christopher McCrum, Marissa H G Gerards, Kiros Karamanidis, Wiebren Zijlstra, Kenneth Meijer
BACKGROUND: Falls are a leading cause of injury among older adults and most often occur during walking. While strength and balance training moderately improve falls risk, training reactive recovery responses following sudden perturbations during walking may be more task-specific for falls prevention. The aim of this review was to determine the variety, characteristics and effectiveness of gait perturbation paradigms that have been used for improving reactive recovery responses during walking and reducing falls among healthy older adults...
2017: European Review of Aging and Physical Activity
Aimi L Forsyth, Serene S Paul, Natalie E Allen, Catherine Sherrington, Victor S C Fung, Colleen G Canning
BACKGROUND AND PURPOSE: Flexed truncal posture is common in people with Parkinson disease (PD); however, little is known about the mechanisms responsible or its effect on physical performance. This cross-sectional study aimed to establish the reliability of a truncal posture measurement and explore relationships between PD impairments and truncal posture, as well as truncal posture and balance and mobility. METHODS: A total of 82 people with PD participated. Truncal posture was measured in standing as the distance between vertebra C7 and a wall...
April 2017: Journal of Neurologic Physical Therapy: JNPT
Michele R Brumley, Pierre A Guertin, Giuliano Taccola
Locomotion is one of the most complex motor behaviors. Locomotor patterns change during early life, reflecting development of numerous peripheral and hierarchically organized central structures. Among them, the spinal cord is of particular interest since it houses the central pattern generator (CPG) for locomotion. This main command center is capable of eliciting and coordinating complex series of rhythmic neural signals sent to motoneurons and to corresponding target-muscles for basic locomotor activity. For a long-time, the CPG has been considered a black box...
2017: Current Pharmaceutical Design
Alison Schinkel-Ivy, Jennifer S Wong, Avril Mansfield
BACKGROUND: Reduced balance confidence is associated with impairments in features of balance and gait in individuals with subacute stroke. However, an understanding of these relationships in individuals at the chronic stage of stroke recovery is lacking. This study aimed to quantify the relationships between balance confidence and specific features of balance and gait in individuals with chronic stroke. METHODS: Participants completed a balance confidence questionnaire and clinical balance assessment (quiet standing, walking, and reactive stepping) at 6 months postdischarge from inpatient stroke rehabilitation...
February 2017: Journal of Stroke and Cerebrovascular Diseases: the Official Journal of National Stroke Association
Alison Schinkel-Ivy, Andrew H Huntley, Elizabeth L Inness, Avril Mansfield
Performance decrements in balance tasks are often observed when a secondary cognitive task is performed simultaneously. This study aimed to determine whether increased cognitive load resulted in altered reactive stepping in individuals with sub-acute stroke, compared to a reactive stepping trial with no secondary task. The secondary purpose was to determine whether differences existed between the first usual-response trial, subsequent usual-response trials, and the dual-task condition. Individuals with sub-acute stroke were exposed to external perturbations to elicit reactive steps...
October 2016: Heliyon
Tejal Kajrolkar, Tanvi Bhatt
Community-dwelling stroke survivors show a high incidence of falls with unexpected external perturbations during dynamic activities like walking. Previous evidence has demonstrated the importance of compensatory stepping to restore dynamic stability in response to perturbations in hemiparetic stroke survivors. However, these studies were limited to either stance perturbations or perturbation induced under the unaffected limb. This study aimed to compare the differences, if any, between the non-paretic and paretic sides in dynamic stability and protective stepping strategies when exposed to unexpected external perturbation during walking...
September 6, 2016: Journal of Biomechanics
Elizabeth L Inness, Avril Mansfield, Mark Bayley, William E McIlroy
BACKGROUND AND PURPOSE: Impaired features of reactive stepping, specifically delays in the early time to foot off (TFO) phase, are associated with increased fall rates after stroke. This study aimed to determine differences in, and determinants of, paretic and nonparetic limb TFO, and to determine whether both paretic and nonparetic TFO were associated with perturbation-evoked falls. METHODS: Retrospective chart review of 105 individuals with stroke was performed within an inpatient rehabilitation setting; each had received a standardized assessment of reactive balance control (in response to a perturbation) at time of discharge...
July 2016: Journal of Neurologic Physical Therapy: JNPT
Francesco Dose, Giuliano Taccola
OBJECTIVES: Explore the primary characteristics of afferent noisy stimuli, which optimally activate locomotor patterns at low intensity. MATERIALS AND METHODS: Intracellular and extracellular electrophysiological traces were derived from single motoneurons and from ventral roots, respectively. From these recordings, we obtained noisy stimulating protocols, delivered to a dorsal root (DR) of an isolated neonatal rat spinal cord, while recording fictive locomotion (FL) from ventral roots...
August 2016: Neuromodulation: Journal of the International Neuromodulation Society
Tyler B Weaver, Stephen N Robinovitch, Andrew C Laing, Yijian Yang
OBJECTIVES: To compare the fall characteristics of individuals with and without Parkinson's disease (PD) through the analysis of real-life falls captured on video. DESIGN: Observational cohort study. SETTING: Two long-term care facilities in British Columbia, Canada. PARTICIPANTS: Individuals living in long-term care (N=306; 16 with PD). MEASUREMENTS: Falls captured on video and analyzed (N=906; 71 in participants with PD)...
January 2016: Journal of the American Geriatrics Society
Yoshiro Okubo, Daniel Schoene, Stephen R Lord
OBJECTIVE: To examine the effects of stepping interventions on fall risk factors and fall incidence in older people. DATA SOURCE: Electronic databases (PubMed, EMBASE, CINAHL, Cochrane, CENTRAL) and reference lists of included articles from inception to March 2015. STUDY SELECTION: Randomised (RCT) or clinical controlled trials (CCT) of volitional and reactive stepping interventions that included older (minimum age 60) people providing data on falls or fall risk factors...
April 2017: British Journal of Sports Medicine
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