scholarly journals Rethinking Margin of Stability: Incorporating Step-To-Step Regulation to Resolve the Paradox

2021 ◽  
Author(s):  
Meghan Kazanski ◽  
Joseph P. Cusumano ◽  
Jonathan B. Dingwell
Keyword(s):  
Inverted Pendulum ◽  
Balance Control ◽  
Center Of Mass ◽  
Frontal Plane ◽  
Lateral Instability ◽  
Foot Placement ◽  
Margin Of Stability ◽  
Increased Risk ◽  
Mediolateral Stability ◽  
Balance Dynamics

ABSTRACTMaintaining frontal-plane stability is a major objective of human walking. Derived from inverted pendulum dynamics, the mediolateral Margin of Stability (MoSML) is frequently used to measure people’s frontal-plane stability on average. However, typical MoSML-based analyses deliver paradoxical interpretations of stability status. To address mediolateral stability using MoSML, we must first resolve this paradox. Here, we developed a novel framework that unifies the well-established inverted pendulum model with Goal-Equivalent Manifold (GEM)-based analyses to assess how humans regulate step-to-step balance dynamics to maintain mediolateral stability. We quantified the extent to which people corrected fluctuations in mediolateral center-of-mass state relative to a MoSML-defined candidate stability GEM in the inverted pendulum phase plane. Participants’ variability and step-to-step correction of tangent and perpendicular deviations from the candidate stability GEM demonstrate that regulation of balance dynamics involves more than simply trying to execute a constant-MoSML balance control strategy. Participants adapted these step-to-step corrections to mediolateral sensory and mechanical perturbations. How participants regulated mediolateral foot placement strongly predicted how they regulated center-of-mass state fluctuations, suggesting that regulation of center-of-mass state occurs as a biomechanical consequence of foot placement regulation. We introduce the Probability of Instability (PoI), a convenient statistic that accounts for step-to-step variance to properly predict instability likelihood on any given future step. Participants increased lateral PoI when destabilized, as expected. These lateral PoI indicated an increased risk of lateral instability, despite larger (i.e., more stable) average MoSML. PoI thereby explicitly predicts instability risk to decisively resolve the existing paradox that arises from conventional MoSML implementations.

Capturability of Inverted Pendulum Gait Model Under Slip Conditions

2018 ◽  
Author(s):  
Marko Mihalec ◽  
Jingang Yi
Keyword(s):  
Reaction Time ◽  
Coefficient Of Friction ◽  
Inverted Pendulum ◽  
Center Of Mass ◽  
Control Input ◽  
Vertical Movements ◽  
Foot Placement ◽  
Slip Conditions ◽  
The Coefficient Of Friction ◽  
Stable Gait

This paper presents a simple inverted pendulum gait model to study walking under slip conditions. The model allows for both the horizontal and vertical movements of the center of mass during normal walking and walking gaits with foot slip. Stability of the system is analyzed using the concept of capturability. Considering foot placement as a control input, we obtain the stable regions which lead to stable gait. The size of those stable regions is used to evaluate the effect of the coefficient of friction and the slip reaction time on capturability. We also analyze the feasibility of recovery from slip gait in relation to the coefficient of friction and the reaction time. The results confirm the effectiveness of the model and the capturability developement.

Adding Light Touch While Walking in Older Adults: Biomechanical and Neuromotor Effects

2020 ◽  
Vol 28 (5) ◽  
pp. 680-685
Author(s):  
Alison R. Oates ◽  
Aaron Awdhan ◽  
Catherine Arnold ◽  
Joyce Fung ◽  
Joel L. Lanovaz
Keyword(s):  
Older Adults ◽  
Muscle Activity ◽  
Balance Control ◽  
Center Of Mass ◽  
Gait Pattern ◽  
Light Touch ◽  
Margin Of Stability ◽  
Complex Picture ◽  
Falls In Older Adults ◽  
Haptic Input

Adding haptic input may improve balance control and help prevent falls in older adults. This study examined the effects of added haptic input via light touch on a railing while walking. Participants (N = 53, 75.9 ± 7.9 years) walked normally or in tandem (heel to toe) with and without haptic input. During normal walking, adding haptic input resulted in a more cautious and variable gait pattern, reduced variability of center of mass acceleration and margin of stability, and increased muscle activity. During tandem walking, haptic input had minimal effect on step parameters, decreased lower limb muscle activity, and increased cocontraction at the ankle closest to the railing. Age was correlated with step width variability, stride length variability, stride velocity, variability of medial-lateral center of mass acceleration, and margin of stability for tandem walking. This complex picture of sensorimotor integration in older adults warrants further exploration into added haptic input during walking.

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.

Validating Determinants for an Alternate Foot Placement Selection Algorithm During Human Locomotion in Cluttered Terrain

2007 ◽  
Vol 98 (4) ◽  
pp. 1928-1940 ◽  
Author(s):  
Renato Moraes ◽  
Fran Allard ◽  
Aftab E. Patla
Keyword(s):  
Dynamic Stability ◽  
Center Of Mass ◽  
Frontal Plane ◽  
Human Locomotion ◽  
The Body ◽  
Selection Algorithm ◽  
Foot Placement ◽  
Double Support ◽  
One Step ◽  
Base Of Support

The goal of this study was to validate dynamic stability and forward progression determinants for the alternate foot placement selection algorithm. Participants were asked to walk on level ground and avoid stepping, when present, on a virtual white planar obstacle. They had a one-step duration to select an alternate foot placement, with the task performed under two conditions: free (participants chose the alternate foot placement that was appropriate) and forced (a green arrow projected over the white planar obstacle cued the alternate foot placement). To validate the dynamic stability determinant, the distance between the extrapolated center of mass (COM) position, which incorporates the dynamics of the body, and the limits of the base of support was calculated in both anteroposterior (AP) and mediolateral (ML) directions in the double support phase. To address the second determinant, COM deviation from straight ahead was measured between adaptive and subsequent steps. The results of this study showed that long and lateral choices were dominant in the free condition, and these adjustments did not compromise stability in both adaptive and subsequent steps compared with the short and medial adjustments, which were infrequent and adversely affected stability. Therefore stability is critical when selecting an alternate foot placement in a cluttered terrain. In addition, changes in the plane of progression resulted in small deviations of COM from the endpoint goal. Forward progression of COM was maintained even for foot placement changes in the frontal plane, validating this determinant as part of the selection algorithm.

Strategies for maintaining dynamic balance in persons with neurological disorders during overground walking

2021 ◽  
pp. 095441192110236
Author(s):  
Tiziana Lencioni ◽  
Denise Anastasi ◽  
Ilaria Carpinella ◽  
Anna Castagna ◽  
Alessandro Crippa ◽  
...  
Keyword(s):  
Neurological Disorder ◽  
Center Of Pressure ◽  
Balance Control ◽  
Dynamic Balance ◽  
Objective Assessment ◽  
Center Of Mass ◽  
Frontal Plane ◽  
Rehabilitation Program ◽  
Lower Limbs ◽  
Lateral Direction

Maintaining a stable gait requires a dynamic balance control, that can be altered in persons with Multiple Sclerosis (MS), Stroke (ST), and Parkinson’s disease (PD). The understanding of the strategy for Center of Mass (CoM) positioning adopted by patients during walking is important to be able to program treatments aimed at improving gait control and preventing falls. Forty-four persons with a mild-to-moderate neurological disorder (20 with MS, 14 with ST, 10 with PD) underwent clinical examination and gait analysis. Ten Healthy Subjects (HS) walking at matched speed provided the normative data. Dynamic balance was assessed using the margin of stability (MoS). It was calculated as the distance between the extrapolated Center of Pressure and the extrapolated CoM at mid-stance. The MoS values for lower limbs were calculated in patients and compared with speed-matched values of HS. Persons with neurological disorder showed increased MoS in the medio-lateral direction with respect to HS. Within-group comparison analysis showed a symmetry between lower limbs in HS (Mean (95%CI) [mm], dominant vs non-dominant limb, 43.3 (31.9–54.6) vs 42.9 (28.8–56.9)) and PD (less affected vs more affected limb, 71.1 (59.8–82.5) vs 72.5 (58.5–86.6)), while a significant asymmetry was found in MS (54.4 (46.4–62.4) vs 81.1 (71.2–91.1)) and ST (52.1 (42.6–61.7) vs 74.7 (62.8–86.6)) participants. The history of falls was comparable among PD, MS, and ST groups, and the MoS in the frontal plane showed a strong correlation with these records. Objective assessment of MoS revealed pathology-specific strategies showing different impacts in MS, ST, and PD on the ability to control CoM information to manage the balance between limbs during gait. MoS evaluation will provide useful information to address a tailored rehabilitation program and to monitor disease progression.

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.

scholarly journals Frontal plane dynamics of the centre of mass during quadrupedal locomotion on a split-belt treadmill

2020 ◽  
Vol 17 (170) ◽  
pp. 20200547 ◽  
Author(s):  
E. M. Latash ◽  
W. H. Barnett ◽  
H. Park ◽  
J. M. Rider ◽  
A. N. Klishko ◽  
...  
Keyword(s):  
Dynamic Stability ◽  
Inverted Pendulum ◽  
Balance Control ◽  
Frontal Plane ◽  
Centre Of Mass ◽  
Vertical Projection ◽  
Quadrupedal Locomotion ◽  
Belt Speed ◽  
Inverted Pendulum Model ◽  
Lateral Displacements

Our previous study of cat locomotion demonstrated that lateral displacements of the centre of mass (COM) were strikingly similar to those of human walking and resembled the behaviour of an inverted pendulum (Park et al. 2019 J. Exp. Biol. 222 , 14. (doi:10.1242/jeb.198648)). Here, we tested the hypothesis that frontal plane dynamics of quadrupedal locomotion are consistent with an inverted pendulum model. We developed a simple mathematical model of balance control in the frontal plane based on an inverted pendulum and compared model behaviour with that of four cats locomoting on a split-belt treadmill. The model accurately reproduced the lateral oscillations of cats' COM vertical projection. We inferred the effects of experimental perturbations on the limits of dynamic stability using data from different split-belt speed ratios with and without ipsilateral paw anaesthesia. We found that the effect of paw anaesthesia could be explained by the induced bias in the perceived position of the COM, and the magnitude of this bias depends on the belt speed difference. Altogether, our findings suggest that the balance control system is actively involved in cat locomotion to provide dynamic stability in the frontal plane, and that paw cutaneous receptors contribute to the representation of the COM position in the nervous system.

scholarly journals The motor repertoire of older adult fallers may constrain their response to balance perturbations

2018 ◽  
Vol 120 (5) ◽  
pp. 2368-2378 ◽  
Author(s):  
Jessica L. Allen ◽  
Jason R. Franz
Keyword(s):  
Older Adults ◽  
Visual Perception ◽  
Older Adult ◽  
Balance Control ◽  
Lateral Instability ◽  
Increased Risk ◽  
Motor Module ◽  
Risk Of Falls ◽  
History Of ◽  
Walking Balance

Older adults are at a high risk of falls, and most falls occur during locomotor activities like walking. This study aimed to improve our understanding of changes in neuromuscular control associated with increased risk of falls in older adults in the presence of dynamic balance challenges during walking. Motor module (also known as muscle synergy) analyses identified changes in the neuromuscular recruitment of leg muscles during walking with and without perturbations designed to elicit the visual perception of lateral instability. During normal walking we found that a history of falls (but not age) was associated with reduced motor module complexity and that age (but not a history of falls) was associated with increased step-to-step variability of module recruitment timing. Furthermore, motor module complexity was unaltered in the presence of optical flow perturbations. The specific effects of a history of falls on leg muscle recruitment included an absence and/or inability to independently recruit motor modules normally recruited to perform biomechanical functions important for walking balance control. These results suggest that fallers do not recruit the appropriate motor modules necessary for well-coordinated walking balance control even in the presence of perturbations. The identified changes in the modular control of walking balance in older fallers may either represent a neural deficit that leads to poor balance control or a prior history of falls that results in a compensatory motor adaptation. In either case, our study provides initial evidence that a reduced motor repertoire in older adult fallers may be a constraint on their ability to appropriately respond to balance challenges during walking. NEW & NOTEWORTHY This is the first study to demonstrate a reduced motor repertoire during walking in older adults with a history of falls but without any overt neurological deficits. Furthermore, using virtual reality during walking to elicit the visual perception of lateral instability, we provide initial evidence that a reduced motor repertoire in older adult fallers may be a constraint on their ability to appropriately respond to balance challenges during walking.

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