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 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 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.

“Fractions of Men”: Engendering Amputation in Victorian Culture

1997 ◽  
Vol 39 (4) ◽  
pp. 742-777 ◽  
Author(s):  
Erin O'Connor
Keyword(s):  
Civil War ◽  
The Body ◽  
Altered State ◽  
Complete Understanding ◽  
Victorian Culture ◽  
After Effects ◽  
The Mind ◽  
The Relationship

In 1866, theAtlantic Monthlypublished a fictional case study of an army surgeon who had lost all of his limbs during the Civil War. Written anonymously by American neurologist Silas Weir Mitchell, “The Case of George Dedlow” describes not only the series of wounds and infections which led to the amputation of all four of the soldier's arms and legs but also the after-effects of amputation. Reduced to what he terms “a useless torso, more like some strange larval creature than anything of human shape,” Dedlow finds that in disarticulating his body, amputation articulates anatomical norms. His observation of his own uniquely altered state qualifies him to speak in universal terms about the relationship between sentience and selfhood: “I have dictated these pages,” he says, “not to shock my readers, but to possess them with facts in regard to the relation of the mind to the body” (1866:5). As such, the story explores the meaning of embodiment, finding in a fragmented anatomy the opportunity to piece together a more complete understanding of how the body functions—physically and metaphysically—as a whole.

scholarly journals Meaningful measurements of maneuvers: People with incomplete spinal cord injury ‘step up’ to the challenges of altered stability requirements

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Wendy L. Ochs ◽  
Jane Woodward ◽  
Tara Cornwell ◽  
Keith E. Gordon
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Force Field ◽  
Force Fields ◽  
Center Of Mass ◽  
Lateral Force ◽  
Step Width ◽  
Incomplete Spinal Cord Injury ◽  
Cord Injury ◽  
The Stability

Abstract Background Many people with incomplete spinal cord injury (iSCI) have the ability to maneuver while walking. However, neuromuscular impairments create challenges to maintain stability. How people with iSCI maintain stability during walking maneuvers is poorly understood. Thus, this study compares maneuver performance in varying external conditions between persons with and without iSCI to better understand maneuver stabilization strategies in people with iSCI. Methods Participants with and without iSCI walked on a wide treadmill and were prompted to perform lateral maneuvers between bouts of straight walking. Lateral force fields applied to the participants’ center of mass amplified or attenuated the participants’ movements, thereby increasing the capability of the study to capture behavior at varied levels of challenge to stability. Results By examining metrics of stability, step width, and center of mass dynamics, distinct strategies emerged following iSCI. The minimum margin of stability (MOSmin) on each step during maneuvers indicated persons with iSCI generally adapted to amplified and attenuated force fields with increased stability compared to persons without iSCI, particularly using increased step width and reduced center of mass excursion on maneuver initiation. In the amplified field, however, persons with iSCI had a reduced MOSmin when terminating a maneuver, likely due to the challenge of the force field opposing the necessary lateral braking. Persons without iSCI were more likely to rely on or oppose the force field when appropriate for movement execution. Compared to persons with iSCI, they reduced their MOSmin to initiate maneuvers in the attenuated and amplified fields and increased their MOSmin to arrest maneuvers in the amplified field. Conclusions The different force fields were successful in identifying relatively subtle strategy differences between persons with and without iSCI. Specifically, persons with iSCI adopted increased step width and reduction in center of mass excursion to increase maneuver stability in the amplified field. The amplified field may provoke practice of stable and efficient initiation and arrest of walking maneuvers. Overall, this work allows better framing of the stability mechanisms used following iSCI to perform walking maneuvers.

Harmonie Force Fields and Bond Orders for Naphthalene, Anthracene, Biphenylene and Perylene with Mean Amplitudes for Perylene

1978 ◽  
Vol 33 (1) ◽  
pp. 45-54 ◽  
Author(s):  
J. C. Whitmer ◽  
S. J. Cyvin ◽  
B. N. Cyvin
Keyword(s):  
Force Field ◽  
Force Fields ◽  
Field Approximation ◽  
Force Constants ◽  
Bond Orders ◽  
Mean Amplitudes Of Vibration ◽  
Complete Set ◽  
First Time ◽  
The Relationship ◽  
Good Agreement

Complete normal coordinate analyses were performed for naphthalene, anthracene, biphenylene and perylene, starting from a simple force field with seven adjustable force constants. A relationship between bond orders and carbon-carbon stretching force constants was deduced from: (a) bond distances as a function of bond orders, (b) a version of Badger's rule relating stretching force constants to the bond distances. The relationship was used to modify the initial seven-parameter force field, and the vibrational frequencies calculated from both the initial and modified force fields are discussed. In general the simple force field approximation produces sets of frequencies in remarkably good agreement with experimental assignments. The force field approximation failed badly when applied to benzene. No obvious explanation was found for this unexpected feature, which makes it worth while to continue the investigations. The mean amplitudes of vibration were calculated. For perylene an account of the complete set of mean amplitudes is given for the first time.

scholarly journals Warholian Repetition and the Viewer’s Affective Response to Artworks from His Death and Disaster Series

Leonardo ◽  
2018 ◽  
Vol 51 (2) ◽  
pp. 138-142
Author(s):  
Jason Kass ◽  
Beth Harland ◽  
Nick Donnelly
Keyword(s):  
Cognitive Processing ◽  
Affective Response ◽  
Repeated Exposure ◽  
Andy Warhol ◽  
Direct Impact ◽  
Affective Experience ◽  
Negative Images ◽  
Car Crashes ◽  
Experimental Findings ◽  
The Relationship

In his Death and Disaster series, Andy Warhol repeated gruesome images of suicides and car crashes. The artist’s use of repetition has been discussed extensively but not in terms of its direct impact on the viewer’s perceptual and cognitive processing. This article considers the viewer’s affective experience resulting from repeated exposure to negative images in artworks from the Death and Disaster series. The authors put forward an account of the potential affective experience of Warholian repetition based on existing experimental findings and by way of the artist’s own remarks on the relationship between repetition and affect.

Contributions to the History of Psychology: XLVIII. Ancient Greek Roots of the Assumptions of Modern Clinical Psychology

1988 ◽  
Vol 66 (3) ◽  
pp. 903-921
Author(s):  
Rosemary A. Robbins
Keyword(s):  
Force Field ◽  
Human Nature ◽  
Clinical Psychology ◽  
Ancient Greece ◽  
Ancient Greek ◽  
Underlying Assumption ◽  
History Of ◽  
The Individual ◽  
Relationship Of ◽  
The Relationship

This paper is an account of studies of the linguistic transformation that took place in ancient Greece between the eighth and fourth centuries B.C., searching for factors which contribute to the shift in how humans perceived themselves. The group or force-field consciousness of the men of the Iliad and the linguistic factors which allowed “individuality” to emerge by the time of Plato is explored. The account relates the emergence of the notion of “madness” to the development of the individual and asks whether madness is an artifact of individuality and explores the relationship of these developments to our present underlying assumption of a duality in human nature composed of the rational and the irrational.

On Some Theoretical Aspects of the 1-Type Doubling Constant qe: Application to XYZ (C∞V) Type Molecules

1974 ◽  
Vol 29 (12) ◽  
pp. 1782-1786
Author(s):  
N. Mohan ◽  
A. Müller
Keyword(s):  
Force Field ◽  
Mass Effect ◽  
Centrifugal Distortion ◽  
The Relationship

The relationship between the 1-type doubling constant qe and the centrifugal distortion constant De and the range of real values of qe for XYZ (C∞v) type molecules, is derived in detail. The experimental value of qe for many molecules is found to be in the neighbourhood of its minimum. The usefulness of qe in fixing a unique and accurate force field for XYZ (C∞v)type molecules is also discussed. A brief discussion of the nature of the errors arising due to the use of Dv , BV and υi in the calculation (for qe) is presented. The study of the mass effect on qe is also reported.

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