scholarly journals Application of a Novel Force-Field to Manipulate the Relationship Between Pelvis Motion and Step Width in Human Walking

2019 ◽  
Vol 27 (10) ◽  
pp. 2051-2058 ◽  
Author(s):  
Lauren N. Heitkamp ◽  
Katy H. Stimpson ◽  
Jesse C. Dean
Keyword(s):  
Force Field ◽  
Human Walking ◽  
Step Width ◽  
The Relationship

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.

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 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.

EXPERIENCE AND PRACTICE IN CARRYING A HEAVY, UNILATERAL LOAD: FOOTPRINT EVIDENCE

2017 ◽  
Vol 17 (01) ◽  
pp. 1750022 ◽  
Author(s):  
DAVID WEBB ◽  
SARA BRATSCH
Keyword(s):  
Anterior Part ◽  
Center Of Mass ◽  
Initial Study ◽  
Ease Of Use ◽  
Human Walking ◽  
Step Width ◽  
Heavy Load ◽  
Subtle Change ◽  
Foot Placement ◽  
Heavy Loads

Although a significant amount of research has examined the biomechanical effects of carrying a load on human walking, most has focussed on fore and aft loads, or evenly balanced loads. In addition, most research on human walking no longer considers footprint analysis, despite its ease of use and its effectiveness in studies of balance. However, one project, with a small number of subjects, suggested that people carrying a heavy load in one hand (e.g., a suitcase or toolbox) make two sorts of adjustments to the placement of their feet on the substrate. The first and most obvious change is a decrease in foot angle (in-toeing) on the unloaded side. This puts the anterior part of the foot further under the center of mass when carrying a load in the contralateral hand and has been amply documented in subsequent studies. The second and more subtle change is a decrease in step width, a practice which also moves the foot on the unloaded side closer to the center of mass. However, tests subsequent to the original study did not show a consistent or significant use of this technique. This discrepancy between original and subsequent results in step width can be explained by the level of expertise which various subjects have. Experience carrying heavy loads may be required for most subjects to develop ways of accommodating loads. For this project, subjects were tested under two conditions: carrying an empty canvas bag; carrying the same bag with 21% of their body weight in it. All subjects walked on paper runners, wearing paint-soaked socks to leave footprint trails. Subjects were asked to walk once with no weights followed by three more times with weights. They were then given 10–15[Formula: see text]min of practice with the weighted bag, then asked to repeat the protocol, for a total of eight trials (two unweighted and six weighted). Foot angle and step width were measured for all trials. Results show that practice does indeed make a difference in the use of a narrower step when carrying a heavy load. Specifically, the first three weighted trials show a decrease in step width that is nonsignificant, but the last three evince a significant reduction as compared to unweighted trials. In addition, lifetime experience carrying a heavy load led to more immediate changes in foot placement. We conclude that the initial study involved subjects who already had experience carrying a unilateral heavy load and that, as with other activities, mechanically more effective movements are acquired with greater experience and practice.

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.

scholarly journals Mechanical and metabolic determinants of the preferred step width in human walking

2001 ◽  
Vol 268 (1480) ◽  
pp. 1985-1992 ◽  
Author(s):  
J. Maxwell Donelan ◽  
Rodger Kram ◽  
Kuo Arthur D.
Keyword(s):  
Human Walking ◽  
Step Width
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