scholarly journals Effects of vestibular stimulation on gait stability and variability

2021 ◽  
Author(s):  
Rina M. Magnani ◽  
Jaap H. van Dieën ◽  
Sjoerd M. Bruijn
Keyword(s):  
Muscle Activity ◽  
Center Of Mass ◽  
Mass Movement ◽  
Stable Condition ◽  
Vestibular Stimulation ◽  
Step Width ◽  
Gait Stability ◽  
Foot Placement ◽  
Vestibular Information ◽  
Narrow Base

AbstractVestibular information modulates muscle activity during gait, presumably to contribute stability, because noisy electrical vestibular stimulation perturbs gait stability. An important mechanism to stabilize gait in the mediolateral direction is to coordinate foot placement based on a sensory estimate of the trunk center of mass state, to which vestibular information appears to contribute. We, therefore expected that noisy vestibular stimulation would decrease the correlation between foot placement and trunk center of mass state. Moreover, as vestibular modulation of muscle activity during gait depends on step width, we expected stronger effects for narrow-base than normal walking, and smaller effects for wide-base walking. In eleven healthy subjects we measured the kinematics of the trunk (as a proxy of the center of mass), and feet, while they walked on a treadmill in six conditions, including three different step widths: control (preferred step width), narrow-base (steps smaller than hip width), and wide-base (with steps greater than hip width). The three conditions were conducted with and without a bipolar electrical stimulus, applied behind the ears (5 mA). Walking with EVS reduced gait stability but increased the foot placement to center of mass correlation in different step width conditions. The narrow-base walking was the most stable condition and showed a stronger correlation between foot placement and center of mass state. We argue that EVS destabilized gait, but that this was partially compensated for by tightened control over foot placement, which would require successful use of other than vestibular sensory inputs, to estimate center of mass movement.

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.

scholarly journals Stabilization Strategies for Fast Walking in Challenging Environments With Incomplete Spinal Cord Injury

2021 ◽  
Vol 2 ◽  
Author(s):  
Tara Cornwell ◽  
Jane Woodward ◽  
Wendy Ochs ◽  
Keith E. Gordon
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Walking Speed ◽  
Center Of Mass ◽  
Lateral Stability ◽  
Step Width ◽  
Incomplete Spinal Cord Injury ◽  
Foot Placement ◽  
Fast Speed ◽  
Cord Injury

Gait rehabilitation following incomplete spinal cord injury (iSCI) often aims to enhance speed and stability. Concurrently increasing both may be difficult though as certain stabilization strategies will be compromised at faster speeds. To evaluate the interaction between speed and lateral stability, we examined individuals with (n = 12) and without (n = 12) iSCI as they performed straight walking and lateral maneuvers at Preferred and Fast treadmill speeds. To better detect the effects of speed on stability, we challenged lateral stability with a movement amplification force field. The Amplification field, created by a cable-driven robot, applied lateral forces to the pelvis that were proportional to the real-time lateral center of mass (COM) velocity. While we expected individuals to maintain stability during straight walking at the Fast speed in normal conditions, we hypothesized that both groups would be less stable in the Amplification field at the Fast speed compared to the Preferred. However, we found no effects of speed or the interaction between speed and field on straight-walking stability [Lyapunov exponent or lateral margin of stability (MOS)]. Across all trials at the Fast speed compared to the Preferred, there was greater step width variability (p = 0.031) and a stronger correlation between lateral COM state at midstance and the subsequent lateral foot placement. These observations suggest that increased stepping variability at faster speeds may be beneficial for COM control. We hypothesized that during lateral maneuvers in the Amplification field, MOS on the Initiation and Termination steps would be smaller at the Fast speed than at the Preferred. We found no effect of speed on the Initiation step MOS within either field (p > 0.350) or group (p > 0.200). The Termination step MOS decreased at the Fast speed within the group without iSCI (p < 0.001), indicating a trade-off between lateral stability and forward walking speed. Unexpectedly, participants took more steps and time to complete maneuvers at the Fast treadmill speed in the Amplification field. This strategy prioritizing stability over speed was especially evident in the group with iSCI. Overall, individuals with iSCI were able to maintain lateral stability when walking fast in balance-challenging conditions but may have employed more cautious maneuver strategies.

scholarly journals The effect of external lateral stabilization on the control of mediolateral stability in walking and running

2018 ◽  
Author(s):  
Mohammadreza Mahaki ◽  
Sjoerd M Bruijn ◽  
Jaap H. van Dieën
Keyword(s):  
Active Control ◽  
Repeated Measures ◽  
Gait Cycle ◽  
Center Of Mass ◽  
Step Width ◽  
Kinematic Data ◽  
Foot Placement ◽  
Consumption Data ◽  
Mediolateral Stability

It is still unclear how humans control mediolateral (ML) stability in walking and even more so for running. Here, foot placement adjustment as a main mechanism of active control of mediolateral stability was compared between walking and running. Moreover, to verify the role of foot placement as a means of active control of ML stability and associated metabolic costs in both modes of locomotion, this study investigated the effect of external lateral stabilization on foot placement control. Ten young adults participated in this study. Kinematic data of the trunk (T6) and feet (heels) as well as breath-by-breath oxygen consumption data were recorded during walking and running on a treadmill in normal and stabilized conditions. Coordination between ML trunk Center of Mass (CoM) state and subsequent ML foot placement, step width, and step width variability were assessed. Two-way repeated measures ANOVAs (either normal or SPM1d) were used to test for effects of walking vs. running and of normal vs. stabilized locomotion. We found a stronger association between ML trunk CoM state and foot placement in walking than in running from 90-100% of the gait cycle and also a higher step width variability in walking, but no significant differences in step width. The association between trunk CoM state and foot placement was significantly decreased by external lateral stabilization in walking and running, and this reduction was stronger in walking than in running from 75-100% of gait cycle. Surprisingly, energy cost significantly increased by external lateral stabilization, which was more pronounced in running than walking. We conclude that ML foot placement is coordinated to the CoM kinematic state to stabilize both walking and running. This coordination is more tight in walking than in running and appears not to contribute substantially to the energy costs of either mode of locomotion.

scholarly journals Greater exposure to repetitive subconcussive head impacts is associated with vestibular dysfunction and balance impairments during walking

Neurology ◽  
2018 ◽  
Vol 91 (23 Supplement 1) ◽  
pp. S27.2-S27
Author(s):  
Fernando Santos ◽  
Jaclyn B Caccese ◽  
Mariana Gongora ◽  
Ian Sotnek ◽  
Elizabeth Kaye ◽  
...  
Keyword(s):  
Center Of Pressure ◽  
Balance Control ◽  
Center Of Mass ◽  
Vestibular Stimulation ◽  
Vestibular Dysfunction ◽  
Foot Placement ◽  
Head Impacts ◽  
Eyes Closed ◽  
Balance Deficits ◽  
Soccer Heading

Exposure to repetitive subconcussive head impacts (RSHI), specifically soccer heading, is associated with white matter microstructural changes and cognitive performance impairments. However, the effect of soccer heading exposure on vestibular processing and balance control during walking has not been studied. Galvanic vestibular stimulation (GVS) is a tool that can be used to probe the vestibular system during standing and walking. The purpose of this study was to investigate the association of soccer heading with subclinical balance deficits during walking. Twenty adult amateur soccer players (10 males and 10 females, 22.3 ± 4.5 years, 170.5 ± 9.8 cm, 70.0 ± 10.5 kg) walked along a foam walkway with the eyes closed under 2 conditions: with GVS (∼40 trials) and without GVS (∼40 trials). Outcome measures included mediolateral center-of-mass (COM), center-of-pressure (COP) separation, foot placement, mediolateral ankle modulation, hip adduction, and ankle push off. For each balance mechanism, a GVS response was calculated (GVS, mean [without GVS]). In addition, participants completed a questionnaire, reporting soccer heading exposure over the past year. A linear regression model was used to determine if vestibular processing and balance during walking were related to RSHI exposure. Both foot placement (R2 = 0.324, p = 0.009) and hip adduction (R2 = 0.183, p = 0.50) were predicted by RSHI; whereby, greater exposure to RSHI was associated with greater foot placement and hip adduction responses. However, COM-COP separation (R2 < 0.001, p = 0.927), ankle modulation (R2 = 0.037, p = 0.417), and push off (R2 < 0.001, p = 0.968) were not related to RSHI exposure. Individuals who were exposed to greater RSHI were more perturbed by vestibular stimulation during walking, suggesting that there may be vestibular dysfunction and balance impairments with frequent heading; specifically, individuals with greater exposure to RSHI responded with larger foot placement and hip adduction responses to GVS.

scholarly journals A novel Movement Amplification environment reveals effects of controlling lateral centre of mass motion on gait stability and metabolic cost

2020 ◽  
Vol 7 (1) ◽  
pp. 190889
Author(s):  
Mengnan/Mary Wu ◽  
Geoffrey L. Brown ◽  
Jane L. Woodward ◽  
Sjoerd M. Bruijn ◽  
Keith E. Gordon
Keyword(s):  
Metabolic Cost ◽  
Mass Motion ◽  
Step Width ◽  
Centre Of Mass ◽  
Cost Of Transport ◽  
Gait Patterns ◽  
Gait Stability ◽  
Foot Placement ◽  
Base Of Support ◽  
Healthy Participants

During human walking, the centre of mass (COM) laterally oscillates, regularly transitioning its position above the two alternating support limbs. To maintain upright forward-directed walking, lateral COM excursion should remain within the base of support, on average. As necessary, humans can modify COM motion through various methods, including foot placement. How the nervous system controls these oscillations and the costs associated with control are not fully understood. To examine how lateral COM motions are controlled, healthy participants walked in a ‘Movement Amplification’ force field that increased lateral COM momentum in a manner dependent on the participant's own motion (forces were applied to the pelvis proportional to and in the same direction as lateral COM velocity). We hypothesized that metabolic cost to control lateral COM motion would increase with the gain of the field. In the Movement Amplification field, participants were significantly less stable than during baseline walking. Stability significantly decreased as the field gain increased. Participants also modified gait patterns, including increasing step width, which increased the metabolic cost of transport as the field gain increased. These results support previous research suggesting that humans modulate foot placement to control lateral COM motion, incurring a metabolic cost.

scholarly journals Small Directional Treadmill Perturbations Induce Differential Gait Stability Adaptation

2021 ◽  
Author(s):  
Jinfeng Li ◽  
Helen J. Huang
Keyword(s):  
Center Of Mass ◽  
Lateral Shift ◽  
Small Magnitude ◽  
Small Perturbations ◽  
Gait Stability ◽  
Foot Placement ◽  
Margin Of Stability ◽  
Belt Speed ◽  
Base Of Support ◽  
Anterior Posterior

Introducing unexpected perturbations to challenge gait stability is an effective approach to investigate balance control strategies. Little is known about the extent to which people can respond to small perturbations during walking. This study aimed to determine how subjects adapted gait stability to multidirectional perturbations with small magnitudes applied on a stride-by-stride basis. Ten healthy young subjects walked on a treadmill that either briefly decelerated belt speed ("stick"), accelerated belt speed ("slip"), or shifted the platform medial-laterally at right leg mid-stance. We quantified gait stability adaptation in both anterior-posterior and medial-lateral directions using margin of stability and its components, base of support and extrapolated center of mass. Gait stability was disrupted upon initially experiencing the small perturbations as margin of stability decreased in the stick, slip, and medial shift perturbations and increased in the lateral shift perturbation. Gait stability metrics were generally disrupted more for perturbations in the coincident direction. As subjects adapted their margin of stability using feedback strategies in response to the small perturbations, subjects primarily used base of support (foot placement) control in the stick and lateral shift perturbations and extrapolated center of mass control in the slip and medial shift perturbations. Gait stability metrics adapted to perturbations in both anterior-posterior and medial-lateral directions. These findings provide new knowledge about the extent of gait stability adaptation to small magnitude perturbations applied on a stride-by-stride basis and reveal potential new approaches for balance training interventions to target foot placement and center of mass control.

scholarly journals Small Directional Treadmill Perturbations Induce Differential Gait Stability Adaptation

2021 ◽  
Author(s):  
Jinfeng Li ◽  
Helen J. Huang
Keyword(s):  
Center Of Mass ◽  
Lateral Shift ◽  
Stick Slip ◽  
Small Magnitude ◽  
Small Perturbations ◽  
Gait Stability ◽  
Foot Placement ◽  
Margin Of Stability ◽  
Belt Speed ◽  
Base Of Support

Introducing unexpected perturbations to challenge gait stability is an effective approach to investigate balance control strategies. Little is known about the extent to which people can respond to small perturbations during walking. This study aimed to determine how subjects adapted gait stability to multidirectional perturbations with small magnitudes applied on a stride-by-stride basis. Ten healthy young subjects walked on a treadmill that either briefly decelerated belt speed ("stick"), accelerated belt speed ("slip"), or shifted the platform medial-laterally at right leg mid-stance. We quantified gait stability adaptation in both anterior-posterior and medial-lateral directions using margin of stability and its components, base of support and extrapolated center of mass. Gait stability was disrupted upon initially experiencing the small perturbations as margin of stability decreased in the stick, slip, and medial shift perturbations and increased in the lateral shift perturbation. Gait stability metrics were generally disrupted more for perturbations in the coincident direction. Subjects employed both feedback and feedforward strategies in response to the small perturbations, but mostly used feedback strategies during adaptation. Subjects primarily used base of support (foot placement) control in the lateral shift perturbation and extrapolated center of mass control in the slip and medial shift perturbations. These findings provide new knowledge about the extent of gait stability adaptation to small magnitude perturbations applied on a stride-by-stride basis and reveal potential new approaches for balance training interventions to target foot placement and center of mass control.

When is Vestibular Information Important During Walking?

2004 ◽  
Vol 92 (3) ◽  
pp. 1269-1275 ◽  
Author(s):  
Leah R. Bent ◽  
J. Timothy Inglis ◽  
Bradford J. McFadyen
Keyword(s):  
Gait Cycle ◽  
Vestibular Stimulation ◽  
Upper Body ◽  
Foot Placement ◽  
Double Support ◽  
Vestibular Information ◽  
Heel Contact ◽  
Somatosensory Input ◽  
Single Support Phase ◽  
Support Phase

Locomotion relies on vision, somatosensory input, and vestibular information. Both vision and somatosensory signals have been shown to be phase dependently modulated during locomotion; however, the regulation of vestibular information has not been investigated in humans. By delivering galvanic vestibular stimulation (GVS) to subjects at either heel contact, mid-stance, or toe-off, it was possible to investigate when vestibular information was important during the gait cycle. The results indicated a difference in the vestibular regulation of upper versus lower body control. Upper body responses to GVS applied at different times did not differ in magnitude for the head ( P = 0.2383), trunk ( P = 0.1473), or pelvis ( P = 0.1732) showing a similar dependence on vestibular information for upper body alignment across the gait cycle. In contrast, foot placement was dependent on the time when stimulation was delivered. Changes in foot placement were significantly larger at heel contact (during the double support phase) than when stimulation was delivered at mid-stance (in the single support phase of the gait cycle; P = 0.0193). These latter results demonstrate, for the first time, evidence of phase-dependent modulation of vestibular information during human walking.

scholarly journals Sensitivity of Dynamic Stability to Changes in Step Width During Treadmill Walking by Young Adults

2012 ◽  
Vol 28 (5) ◽  
pp. 616-621 ◽  
Author(s):  
Noah J. Rosenblatt ◽  
Christopher P. Hurt ◽  
Mark D. Grabiner
Keyword(s):  
Motor System ◽  
Center Of Mass ◽  
Treadmill Walking ◽  
Step Width ◽  
Foot Placement ◽  
Before And After ◽  
Theoretical Predictions ◽  
Young Subjects ◽  
Minimum Margin ◽  
Experimental Findings

Recent experimental findings support theoretical predictions that across walking conditions the motor system chooses foot placement to achieve a constant minimum “margin of stability” (MOSmin)—distance between the extrapolated center of mass and base of support. For example, while step width varies, similar average MOSmin exists between overground and treadmill walking and between overground and compliant/irregular surface walking. However, predictions regarding the invariance of MOSmin to step-by-step changes in foot placement cannot be verified by average values. The purpose of this study was to determine average changes in, and the sensitivity of MOSmin to varying step widths during two walking tasks. Eight young subjects walked on a dual-belt treadmill before and after receiving information that stepping on the physical gap between the belts causes no adverse effects. Information decreased step width by 17% (p = .01), whereas MOSmin was unaffected (p = .12). Regardless of information, subject-specific regressions between step-by-step values of step width and MOSmin explained, on average, only 5% of the shared variance (β = 0.11 ± 0.05). Thus, MOSmin appears to be insensitive to changing step width. Accordingly, during treadmill walking, step width is chosen to maintain MOSmin. If MOSmin remains insensitive to step width across other dynamic tasks, then assessing an individual’s stability while performing theses tasks could help describe the health of the motor system.

scholarly journals A neuromechanical strategy for mediolateral foot placement in walking humans

2014 ◽  
Vol 112 (2) ◽  
pp. 374-383 ◽  
Author(s):  
Bradford L. Rankin ◽  
Stephanie K. Buffo ◽  
Jesse C. Dean
Keyword(s):  
Muscle Activity ◽  
Center Of Mass ◽  
Frontal Plane ◽  
Gluteus Medius ◽  
Swing Phase ◽  
Electromyographic Activity ◽  
Mechanical State ◽  
Foot Placement ◽  
The Right ◽  
Clinical Populations

Stability is an important concern during human walking and can limit mobility in clinical populations. Mediolateral stability can be efficiently controlled through appropriate foot placement, although the underlying neuromechanical strategy is unclear. We hypothesized that humans control mediolateral foot placement through swing leg muscle activity, basing this control on the mechanical state of the contralateral stance leg. Participants walked under Unperturbed and Perturbed conditions, in which foot placement was intermittently perturbed by moving the right leg medially or laterally during the swing phase (by ∼50–100 mm). We quantified mediolateral foot placement, electromyographic activity of frontal-plane hip muscles, and stance leg mechanical state. During Unperturbed walking, greater swing-phase gluteus medius (GM) activity was associated with more lateral foot placement. Increases in GM activity were most strongly predicted by increased mediolateral displacement between the center of mass (CoM) and the contralateral stance foot. The Perturbed walking results indicated a causal relationship between stance leg mechanics and swing-phase GM activity. Perturbations that reduced the mediolateral CoM displacement from the stance foot caused reductions in swing-phase GM activity and more medial foot placement. Conversely, increases in mediolateral CoM displacement caused increased swing-phase GM activity and more lateral foot placement. Under both Unperturbed and Perturbed conditions, humans controlled their mediolateral foot placement by modulating swing-phase muscle activity in response to the mechanical state of the contralateral leg. This strategy may be disrupted in clinical populations with a reduced ability to modulate muscle activity or sense their body's mechanical state.

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