Active foot placement control ensures stable gait: Effect of constraints on foot placement and ankle moments

Step-by-step foot placement control, relative to the center of mass (CoM) kinematic state, is generally considered a dominant mechanism for maintenance of gait stability. By adequate (mediolateral) positioning of the center of pressure with respect to the CoM, the ground reaction force generates a moment that prevents falling. In healthy individuals, foot placement is complemented mainly by ankle moment control ensuring stability. To evaluate possible compensatory relationships between step-by-step foot placement and complementary ankle moments, we investigated the degree of (active) foot placement control during steady-state walking, and under either foot placement-, or ankle moment constraints. Thirty healthy participants walked on a treadmill, while full-body kinematics, ground reaction forces and EMG activities were recorded. As a replication of earlier findings, we first showed step-by-step foot placement is associated with preceding CoM state and hip ab-/adductor activity during steady-state walking. Tight control of foot placement appears to be important at normal walking speed because there was a limited change in the degree of foot placement control despite the presence of a foot placement constraint. At slow speed, the degree of foot placement control decreased substantially, suggesting that tight control of foot placement is less essential when walking slowly. Step-by-step foot placement control was not tightened to compensate for constrained ankle moments. Instead compensation was achieved through increases in step width and stride frequency.

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Active foot placement control ensures stable gait: Effect of constraints on foot placement and ankle moments

10.1101/2020.06.10.143867 ◽

2020 ◽

Cited By ~ 1

Author(s):

A.M. van Leeuwen ◽

J.H. van Dieën ◽

A. Daffertshofer ◽

S.M. Bruijn

Keyword(s):

Steady State ◽

Center Of Pressure ◽

Center Of Mass ◽

Reaction Force ◽

Stride Frequency ◽

Tight Control ◽

Foot Placement ◽

Ankle Moment ◽

Reaction Forces ◽

Moment Control

AbstractStep-by-step foot placement control, relative to the center of mass (CoM) kinematic state, is generally considered a dominant mechanism for maintenance of gait stability. By adequate (mediolateral) positioning of the center of pressure with respect to the CoM, the ground reaction force generates a moment that prevents falling. In healthy individuals, foot placement is complemented mainly by ankle moment control ensuring stability. To evaluate possible compensatory relationships between step-by-step foot placement and complementary ankle moments, we investigated the degree of (active) foot placement control during steady-state walking, and under either foot placement-, or ankle moment constraints. Thirty healthy participants walked on a treadmill, while full-body kinematics, ground reaction forces and EMG activities were recorded. As a replication of earlier findings, we first showed step-by-step foot placement is associated with preceding CoM state and hip ab-/adductor activity during steady-state walking. Tight control of foot placement appears to be important at normal walking speed because there was a limited change in the degree of foot placement control despite the presence of a foot placement constraint. At slow speed, the degree of foot placement control decreased substantially, suggesting that tight control of foot placement is less essential when walking slowly. Step-by-step foot placement control was not tightened to compensate for constrained ankle moments. Instead compensation was achieved through increases in step width and stride frequency.

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Ankle muscles activate: mediolateral center of pressure control ensures stable gait

10.1101/2021.03.31.437904 ◽

2021 ◽

Author(s):

Anina Moira van Leeuwen ◽

Jaap H van Dieen ◽

Andreas Daffertshofer ◽

Sjoerd M Bruijn

Keyword(s):

Steady State ◽

Center Of Pressure ◽

Center Of Mass ◽

Reaction Force ◽

Negative Relationship ◽

Pressure Control ◽

Foot Placement ◽

Ankle Moment ◽

Ankle Muscle ◽

Moment Control

During steady-state walking mediolateral gait stability can be maintained by controlling the center of pressure (CoP). The CoP modulates the moment of the ground reaction force, which brakes and reverses movement of the center of mass (CoM) towards the lateral border of the base of support. In addition to foot placement, ankle moments serve to control the CoP. We hypothesized that, during steady-state walking, single stance ankle moments establish a CoP shift to correct for errors in foot placement. We expected ankle muscle activity to be associated with this complementary CoP shift. During treadmill walking, full-body kinematics, ground reaction forces and electromyography were recorded in thirty healthy participants. We found a negative relationship between preceding foot placement error and CoP displacement during single stance. Too medial steps were compensated for by a lateral CoP shift and vice versa, too lateral steps were compensated for by a medial CoP shift. Peroneus longus, soleus and tibialis anterior activity correlated with these CoP shifts. As such, we identified an (active) ankle strategy during steady-state walking. As expected, absolute explained CoP variance by foot placement error decreased when walking with shoes constraining ankle moments. Yet, contrary to our expectations that ankle moment control would compensate for constrained foot placement, the absolute explained CoP variance by foot placement error did not increase when foot placement was constrained. We argue that this lack of compensation reflects the interdependent nature of ankle moment and foot placement control. We suggest that single stance ankle moments do not only compensate for preceding foot placement errors, but also assist control of the subsequent foot placement. Foot placement and ankle moment control are caught in a circular relationship, in which constraints imposed on one will also influence the other.

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Ankle muscles drive mediolateral center of pressure control to ensure stable steady state gait

Scientific Reports ◽

10.1038/s41598-021-00463-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

A. M. van Leeuwen ◽

J. H. van Dieën ◽

A. Daffertshofer ◽

S. M. Bruijn

Keyword(s):

Steady State ◽

Center Of Pressure ◽

Center Of Mass ◽

Reaction Force ◽

Negative Relationship ◽

Pressure Control ◽

Stable Steady State ◽

Foot Placement ◽

Ankle Moment ◽

Moment Control

AbstractDuring steady-state walking, mediolateral gait stability can be maintained by controlling the center of pressure (CoP). The CoP modulates the moment of the ground reaction force, which brakes and reverses movement of the center of mass (CoM) towards the lateral border of the base of support. In addition to foot placement, ankle moments serve to control the CoP. We hypothesized that, during steady-state walking, single stance ankle moments establish a CoP shift to correct for errors in foot placement. We expected ankle muscle activity to be associated with this complementary CoP shift. During treadmill walking, full-body kinematics, ground reaction forces and electromyography were recorded in thirty healthy participants. We found a negative relationship between preceding foot placement error and CoP displacement during single stance; steps that were too medial were compensated for by a lateral CoP shift and vice versa, steps that were too lateral were compensated for by a medial CoP shift. Peroneus longus, soleus and tibialis anterior activity correlated with these CoP shifts. As such, we identified an (active) ankle strategy during steady-state walking. As expected, absolute explained CoP variance by foot placement error decreased when walking with shoes constraining ankle moments. Yet, contrary to our expectations that ankle moment control would compensate for constrained foot placement, the absolute explained CoP variance by foot placement error did not increase when foot placement was constrained. We argue that this lack of compensation reflects the interdependent nature of ankle moment and foot placement control. We suggest that single stance ankle moments do not only compensate for preceding foot placement errors, but also assist control of the subsequent foot placement. Foot placement and ankle moment control are ‘caught’ in a circular relationship, in which constraints imposed on one will also influence the other.

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The effect of constraining mediolateral ankle moments and foot placement on the use of the counter-rotation mechanism during walking

10.1101/2021.12.14.472551 ◽

2021 ◽

Author(s):

Maud van den Bogaart ◽

Sjoerd M. Bruijn ◽

Joke Spildooren ◽

Jaap H. van Dieën ◽

Pieter Meyns

Keyword(s):

Steady State ◽

Center Of Pressure ◽

Center Of Mass ◽

Reaction Force ◽

Force Plate ◽

Gait Pattern ◽

Task Constraints ◽

Foot Placement ◽

Counter Rotation ◽

Body Kinematic

Stability during walking can be maintained by shifts of the Center of Pressure through modulation of foot placement and ankle moments (CoP-mechanism). An additional mechanism to stabilize gait, is the counter-rotation mechanism i.e. changing the angular momentum of segments around the Center of Mass (CoM) to change the direction of the ground reaction force. It is unknown if and how humans use the counter-rotation mechanism to control the CoM during walking and how this interacts with the CoP-mechanism. Thirteen healthy adults walked on a treadmill, while full-body kinematic and force plate data were obtained. The contributions of the CoP and the counter-rotation mechanisms to control the CoM were calculated during steady-state walking, walking on LesSchuh, i.e. constraining mediolateral CoP shifts underneath the stance foot and walking on LesSchuh at 50% of normal step width, constraining both foot placement and ankle mechanisms (LesSchuh50%). A decreased magnitude of within-stride control by the CoP-mechanism was compensated for by an increased magnitude of within-stride control by the counter-rotation mechanism during LesSchuh50% compared to steady-state walking. This suggests that the counter-rotation mechanism is used to stabilize gait when needed. However, the mean contribution of the counter-rotation mechanism over strides did not increase during LesSchuh50% compared to steady-state walking. The CoP-mechanism was the main contributor to the total CoM acceleration. The use of the counter-rotation mechanism may be limited because angular accelerations ultimately need to be reversed and because of interference with other task constraints, such as head stabilization and preventing interference with the gait pattern.

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Simulating bipedal walking using a translating center of pressure

10.1101/723445 ◽

2019 ◽

Author(s):

Karna Potwar ◽

Dongheui Lee

Keyword(s):

Steady State ◽

Walking Speed ◽

Center Of Pressure ◽

Reaction Force ◽

Bipedal Walking ◽

Upper Body ◽

Foot Placement ◽

Fast Walking ◽

Walking Speeds ◽

Steady State Solutions

AbstractDuring walking, foot orientation and foot placement allow humans to stabilize their gait and to move forward. Consequently the upper body adapts to the ground reaction force (GRF) transmitted through the feet. The foot-ground contact is often modeled as a fixed pivot in bipedal models for analysis of locomotion. The fixed pivot models, however, cannot capture the effect of shift in the pivot point from heel to toe. In this study, we propose a novel bipedal model, called SLIPCOP, which employs a translating center of pressure (COP) in a spring loaded inverted pendulum (SLIP) model. The translating COP has two modes: one with a constant speed of translation and the other as the weighted function of the GRF in the fore aft direction. We use the relation between walking speed and touchdown (TD) angle as well as walking speed and COP speed, from existing literature, to restrict steady state solutions within the human walking domain. We find that with these relations, SLIPCOP provides steady state solutions for very slow to very fast walking speeds unlike SLIP. SLIPCOP for normal to very fast walking speed shows good accuracy in estimating COM amplitude and swing stance ratio. SLIPCOP is able to estimate the distance traveled by the COP during stance with high precision.

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The effect of anteroposterior perturbations on the control of the center of mass during treadmill walking

10.1101/848853 ◽

2019 ◽

Author(s):

Maud van den Bogaart ◽

Sjoerd M. Bruijn ◽

Jaap H. van Dieën ◽

Pieter Meyns

Keyword(s):

Center Of Pressure ◽

Center Of Mass ◽

Reaction Force ◽

Force Plate ◽

Gait Pattern ◽

Therapeutic Interventions ◽

Heel Strike ◽

Foot Placement ◽

Relative Contribution ◽

Counter Rotation

AbstractShifts of the center of pressure (CoP) through modulation of foot placement and ankle moments (CoP-mechanism) cause accelerations of the center of mass (CoM) that can be used to stabilize gait. An additional mechanism that can be used to stabilize gait, is the counter-rotation mechanism, i.e., changing the angular momentum of segments around the CoM to change the direction of the ground reaction force. The relative contribution of these mechanisms to the control of the CoM is unknown. Therefore, we aimed to determine the relative contribution of these mechanisms to control the CoM in the anteroposterior (AP) direction during a normal step and the first recovery step after perturbation in healthy adults. Nineteen healthy subjects walked on a split-belt treadmill and received unexpected belt acceleration perturbations of various magnitudes applied immediately after right heel-strike. Full-body kinematic and force plate data were obtained to calculate the contributions of the CoP-mechanism and the counter-rotation mechanism to control the CoM. We found that the CoP-mechanism contributed to corrections of the CoM acceleration after the AP perturbations, while the counter-rotation mechanism actually contributed to CoM acceleration in the direction of the perturbation, but only in the initial phases of the first step after the perturbation. The counter-rotation mechanism appeared to prevent interference with the gait pattern, rather than using it to control the CoM after the perturbation. Understanding the mechanisms used to stabilize gait may have implications for the design of therapeutic interventions that aim to decrease fall incidence.Summary statementUnderstanding the mechanisms used to stabilize gait during unperturbed and perturbed walking may have implications for the design of therapeutic interventions that aim to decrease fall incidence.

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Effects of additional load at different heights on gait initiation: A statistical parametric mapping of center of pressure and center of mass behavior

PLoS ONE ◽

10.1371/journal.pone.0242892 ◽

2021 ◽

Vol 16 (6) ◽

pp. e0242892

Author(s):

Marcus Fraga Vieira ◽

Fábio Barbosa Rodrigues ◽

Alfredo de Oliveira Assis ◽

Eduardo de Mendonça Mesquita ◽

Thiago Santana Lemes ◽

...

Keyword(s):

Time Series ◽

Center Of Pressure ◽

Center Of Mass ◽

Statistical Parametric Mapping ◽

Gait Initiation ◽

Experimental Conditions ◽

Distributed Load ◽

Uniformly Distributed Load ◽

Reaction Forces ◽

Controlled Object

The purpose of this study was to investigate the effects of different vertical positions of an asymmetrical load on the anticipatory postural adjustments phase of gait initiation. Sixty-eight college students (32 males, 36 females; age: 23.65 ± 3.21 years old; weight: 69.98 ± 8.15 kg; height: 1.74 ± 0.08 m) were enrolled in the study. Ground reaction forces and moments were collected using two force platforms. The participants completed three trials under each of the following random conditions: no-load (NL), waist uniformly distributed load (WUD), shoulder uniformly distributed load (SUD), waist stance foot load (WST), shoulder stance foot load (SST), waist swing foot load (WSW), and shoulder swing foot load (SSW). The paired Hotelling’s T-square test was used to compare the experimental conditions. The center of pressure (COP) time series were significantly different for the SUD vs. NL, SST vs. NL, WST vs. NL, and WSW vs. NL comparisons. Significant differences in COP time series were observed for all comparisons between waist vs. shoulder conditions. Overall, these differences were greater when the load was positioned at the shoulders. For the center of mass (COM) time series, significant differences were found for the WUD vs. NL and WSW vs. NL conditions. However, no differences were observed with the load positioned at the shoulders. In conclusion, only asymmetrical loading at the waist produced significant differences, and the higher the extra load, the greater the effects on COP behavior. By contrast, only minor changes were observed in COM behavior, suggesting that the changes in COP (the controller) behavior are adjustments to maintain the COM (controlled object) unaltered.

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Dynamic Balancing Responses in Unilateral Transtibial Amputees Following Outward-Directed Perturbations During Slow Treadmill Walking Differ Considerably for Amputated and Non-Amputated Side

10.21203/rs.3.rs-244733/v1 ◽

2021 ◽

Author(s):

Andrej Olenšek ◽

Matjaž Zadravec ◽

Helena Burger ◽

Zlatko Matjačić

Keyword(s):

Stance Phase ◽

Center Of Pressure ◽

Center Of Mass ◽

Reaction Force ◽

Dynamic Balancing ◽

Transtibial Amputation ◽

Control Subjects ◽

Foot Strike ◽

Transtibial Amputees ◽

Proprioceptive Function

Abstract BackgroundDue to disrupted motor and proprioceptive function lower limb amputation imposes considerable challenges associated with balance and greatly increases risk of falling in case of perturbations during walking. The aim of this study was to investigate dynamic balancing responses in unilateral transtibial amputees when they were subjected to perturbing pushes to the pelvis in outward direction at the time of foot strike on non-amputated and amputated side during slow walking.MethodsFourteen subjects with unilateral transtibial amputation and nine control subjects participated in the study. They were subjected to perturbations that were delivered to the pelvis at the time of foot strike of either the left or right leg. We recorded trajectories of center of pressure and center of mass, durations of in-stance and stepping periods as well as ground reaction forces. Statistical analysis was performed to determine significant differences in dynamic balancing responses between control subjects and subjects with amputation when subjected to outward-directed perturbation upon entering stance phases with non-amputated or amputated side.ResultsWhen outward-directed perturbations were delivered at the time of foot strike of the non-amputated leg, subjects with amputation were able to modulate center of pressure and ground reaction force similarly as control subjects which indicates application of in-stance balancing strategies. On the other hand, there was a complete lack of in-stance response when perturbations were delivered when the amputated leg entered the stance phase. Subjects with amputations instead used the stepping strategy and adjusted placement of the non-amputated leg in the ensuing stance phase to make a cross-step. Such response resulted in significantly higher displacement of center of mass. ConclusionsResults of this study suggest that due to the absence of the COP modulation mechanism, which is normally supplied by ankle motor function, people with unilateral transtibial amputation are compelled to choose the stepping strategy over in-stance strategy when they are subjected to outward-directed perturbation on the amputated side. However, the stepping response is less efficient than in-stance response. To improve their balancing responses to unexpected balance perturbation people fitted with passive transtibial prostheses should undergo perturbation-based balance training during clinical rehabilitation.

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Mechanics of a rapid running insect: two-, four- and six-legged locomotion

Journal of Experimental Biology ◽

10.1242/jeb.156.1.215 ◽

1991 ◽

Vol 156 (1) ◽

pp. 215-231 ◽

Cited By ~ 39

Author(s):

R. J. Full ◽

M. S. Tu

Keyword(s):

Periplaneta Americana ◽

Mechanical Energy ◽

Center Of Mass ◽

Reaction Force ◽

Metabolic Cost ◽

Legged Locomotion ◽

American Cockroach ◽

Stride Frequency ◽

Gravitational Potential Energy ◽

Vertical Ground Reaction Force

To examine the effects of variation in body form on the mechanics of terrestrial locomotion, we used a miniature force platform to measure the ground reaction forces of the smallest and, relative to its mass, one of the fastest invertebrates ever studied, the American cockroach Periplaneta americana (mass = 0.83 g). From 0.44-1.0 ms-1, P. americana used an alternating tripod stepping pattern. Fluctuations in gravitational potential energy and horizontal kinetic energy of the center of mass were nearly in phase, characteristic of a running or bouncing gait. Aerial phases were observed as vertical ground reaction force approached zero at speeds above 1 ms-1. At the highest speeds (1.0-1.5 ms-1 or 50 body lengths per second), P. americana switched to quadrupedal and bipedal running. Stride frequency approached the wing beat frequencies used during flight (27 Hz). High speeds were attained by increasing stride length, whereas stride frequency showed little increase with speed. The mechanical power used to accelerate the center of mass increased curvilinearly with speed. The mass-specific mechanical energy used to move the center of mass a given distance was similar to that measured for animals five orders of magnitude larger in mass, but was only one-hundredth of the metabolic cost.

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Mechanics of six-legged runners

Journal of Experimental Biology ◽

10.1242/jeb.148.1.129 ◽

1990 ◽

Vol 148 (1) ◽

pp. 129-146 ◽

Cited By ~ 28

Author(s):

R. J. Full ◽

M. S. Tu

Keyword(s):

Mechanical Energy ◽

Center Of Mass ◽

Force Production ◽

Stride Frequency ◽

Gravitational Potential Energy ◽

Vertical Force ◽

Body Form ◽

Blaberus Discoidalis ◽

Ghost Crabs ◽

Reaction Forces

Six-legged pedestrians, cockroaches, use a running gait during locomotion. The gait was defined by measuring ground reaction forces and mechanical energy fluctuations of the center of mass in Blaberus discoidalis (Serville) as they travelled over a miniature force platform. These six-legged animals produce horizontal and vertical ground-reaction patterns of force similar to those found in two-, four- and eight-legged runners. Lateral forces were less than half the vertical force fluctuations. At speeds between 0.08 and 0.66 ms-1, horizontal kinetic and gravitational potential energy changes were in phase. This pattern of energy fluctuation characterizes the bouncing gaits used by other animals that run. Blaberus discoidalis attained a maximum sustainable stride frequency of 13 Hz at 0.35 ms-1, the same speed and frequency predicted for a mammal of the same mass. Despite differences in body form, the mass-specific energy used to move the center of mass a given distance (0.9 J kg-1m-1) was the same for cockroaches, ghost crabs, mammals, and birds. Similarities in force production, stride frequency and mechanical energy production during locomotion suggest that there may be common design constraints in terrestrial locomotion which scale with body mass and are relatively independent of body form, leg number and skeletal type.

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