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

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.

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Associations Between Foot Placement Asymmetries and Metabolic Cost of Transport in Hemiparetic Gait

Neurorehabilitation and Neural Repair ◽

10.1177/1545968316675428 ◽

2016 ◽

Vol 31 (2) ◽

pp. 168-177 ◽

Cited By ~ 17

Author(s):

James M. Finley ◽

Amy J. Bastian

Keyword(s):

Walking Speed ◽

Metabolic Cost ◽

Positive Association ◽

Stroke Survivor ◽

Gas Analysis ◽

Stroke Survivors ◽

Cost Of Transport ◽

Foot Placement ◽

Hemiparetic Gait ◽

All Speeds

Stroke survivors often have a slow, asymmetric walking pattern. They also walk with a higher metabolic cost than healthy, age-matched controls. It is often assumed that spatial-temporal asymmetries contribute to the increased metabolic cost of walking poststroke. However, elucidating this relationship is made challenging because of the interdependence between spatial-temporal asymmetries, walking speed, and metabolic cost. Here, we address these potential confounds by measuring speed-dependent changes in metabolic cost and implementing a recently developed approach to dissociate spatial versus temporal contributions to asymmetry in a sample of stroke survivors. We used expired gas analysis to compute the metabolic cost of transport (CoT) for each participant at 4 different walking speeds: self-selected speed, 80% and 120% of their self-selected speed, and their fastest comfortable speed. We also computed CoT for a sample of age- and gender-matched control participants who walked at the same speeds as their matched stroke survivor. Kinematic data were used to compute the magnitude of a number of variables characterizing spatial-temporal asymmetries. Across all speeds, stroke survivors had a higher CoT than controls. We also found that our sample of stroke survivors did not choose a self-selected speed that minimized CoT, contrary to typical observations in healthy controls. Multiple regression analyses revealed negative associations between speed and CoT and a positive association between asymmetries in foot placement relative to the trunk and CoT. These findings suggest that interventions designed to increase self-selected walking speed and reduce foot-placement asymmetries may be ideal for improving walking economy poststroke.

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Gait Parameter Adjustments for Walking on a Treadmill at Preferred, Slower, and Faster Speeds in Older Adults with Down Syndrome

Current Gerontology and Geriatrics Research ◽

10.1155/2012/782671 ◽

2012 ◽

Vol 2012 ◽

pp. 1-7 ◽

Cited By ~ 3

Author(s):

Beth A. Smith ◽

Masayoshi Kubo ◽

Beverly D. Ulrich

Keyword(s):

Older Adults ◽

Down Syndrome ◽

Stride Frequency ◽

Gait Patterns ◽

Gait Stability ◽

Foot Placement ◽

Gait Parameters ◽

Younger Age ◽

All Speeds ◽

Walking Speeds

The combined effects of ligamentous laxity, hypotonia, and decrements associated with aging lead to stability-enhancing foot placement adaptations during routine overground walking at a younger age in adults with Down syndrome (DS) compared to their peers with typical development (TD). Our purpose here was to examine real-time adaptations in older adults with DS by testing their responses to walking on a treadmill at their preferred speed and at speeds slower and faster than preferred. We found that older adults with DS were able to adapt their gait to slower and faster than preferred treadmill speeds; however, they maintained their stability-enhancing foot placements at all speeds compared to their peers with TD. All adults adapted their gait patterns similarly in response to faster and slower than preferred treadmill-walking speeds. They increased stride frequency and stride length, maintained step width, and decreased percent stance as treadmill speed increased. Older adults with DS, however, adjusted their stride frequencies significantly less than their peers with TD. Our results show that older adults with DS have the capacity to adapt their gait parameters in response to different walking speeds while also supporting the need for intervention to increase gait stability.

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Medial-lateral centre of mass displacement and base of support are equally good predictors of metabolic cost in amputee walking

Gait & Posture ◽

10.1016/j.gaitpost.2016.09.024 ◽

2017 ◽

Vol 51 ◽

pp. 41-46 ◽

Cited By ~ 12

Author(s):

R.A. Weinert-Aplin ◽

M. Twiste ◽

H.L. Jarvis ◽

A.N. Bennett ◽

R.J. Baker

Keyword(s):

Metabolic Cost ◽

Centre Of Mass ◽

Mass Displacement ◽

Base Of Support

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Simulated hemiparesis increases optimal spatiotemporal gait asymmetry but not metabolic cost

10.1101/2021.12.20.473515 ◽

2021 ◽

Author(s):

Russell T Johnson ◽

Nicholas August Bianco ◽

James Finley

Keyword(s):

Gait Speed ◽

Metabolic Cost ◽

The Body ◽

Musculoskeletal Modeling ◽

Cost Of Transport ◽

Gait Patterns ◽

Post Stroke ◽

The Cost ◽

Future Work ◽

Isometric Muscle

Several neuromuscular impairments, such as weakness (hemiparesis), occur after an individual has a stroke, and these impairments primarily affect one side of the body more than the other. Predictive musculoskeletal modeling presents an opportunity to investigate how a specific impairment affects gait performance post-stroke. Therefore, our aim was to use to predictive simulation to quantify the spatiotemporal asymmetries and changes to metabolic cost that emerge when muscle strength is unilaterally reduced. We also determined how forced spatiotemporal symmetry affects metabolic cost. We modified a 2-D musculoskeletal model by uniformly reducing the peak isometric muscle force in all muscles unilaterally. We then solved optimal control simulations of walking across a range of speeds by minimizing the sum of the cubed muscle excitations across all muscles. Lastly, we ran additional optimizations to test if reducing spatiotemporal asymmetry would result in an increase in metabolic cost. Our results showed that the magnitude and direction of effort-optimal spatiotemporal asymmetries depends on both the gait speed and level of weakness. Also, the optimal metabolic cost of transport was 1.25 m/s for the symmetrical and 20% weakness models but slower (1.00 m/s) for the 40% and 60% weakness models, suggesting that hemiparesis can account for a portion of the slower gait speed seen in people post-stroke. Adding spatiotemporal asymmetry to the cost function resulted in small increases (~4%) in metabolic cost. Overall, our results indicate that spatiotemporal asymmetry may be optimal for people post-stroke, who have asymmetrical neuromuscular impairments. Additionally, the effect of speed and level of weakness on spatiotemporal asymmetry may explain the well-known heterogenous distribution of spatiotemporal asymmetries observed in the clinic. Future work could extend our results by testing the effects of other impairments on optimal gait strategies, and therefore build a more comprehensive understanding of the gait patterns in people post-stroke.

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Small Directional Treadmill Perturbations Induce Differential Gait Stability Adaptation

10.1101/2021.02.27.433210 ◽

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.

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Small Directional Treadmill Perturbations Induce Differential Gait Stability Adaptation

Journal of Neurophysiology ◽

10.1152/jn.00091.2021 ◽

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.

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Effects of vestibular stimulation on gait stability and variability

10.1101/2021.09.09.459650 ◽

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.

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Does the margin of stability measure predict stability of gait with a constrained base of support?

10.1101/646943 ◽

2019 ◽

Author(s):

Lakshdeep Gill ◽

Andrew H. Huntley ◽

Avril Mansfield

Keyword(s):

Motion Capture ◽

Three Dimensional ◽

Centre Of Mass ◽

Narrow Beam ◽

Margin Of Stability ◽

Stability Measure ◽

Subsequent Step ◽

Base Of Support ◽

Mass Position ◽

Healthy Participants

ABSTRACTThis study aimed to determine the validity of the centre of mass position (COM) position and extrapolated COM (XCOM), relative to the base of support, for predicting stability during a walking task where the base of support is constrained. Nine young healthy participants walked on a narrow beam. Three-dimensional motion capture was used to calculate the COM and XCOM relative to the base of support. Steps were classified as having either the COM or XCOM inside or outside the base of support, and were classified as successful (stable – foot placed on the beam) or failed (unstable – foot stepped off the beam). If the COM or XCOM are valid measures of stability, they should be within the base of support for successful steps and outside the base of support for failed steps. Classifying the COM and XCOM inside or outside the base of support correctly predicted successful or failed steps in 69% and 58% of cases, respectively. When the COM or XCOM were outside the base of support, walking faster seemed to help participants to maintain stability. The further the COM or XCOM were outside the base of support during a successful step, the more likely participants were to fail on a subsequent step. The results of this study suggest that both COM and XCOM are valid measures of stability during a beam walking task, but that classifying COM and XCOM as inside or outside the base of support may be over-simplistic.

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