Ankle Control in Walking and Running: Speed- and Gait-Related Changes in Dynamic Mean Ankle Moment Arm

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Peter Gabriel Adamczyk
Keyword(s):  
High Speed ◽  
Center Of Pressure ◽  
Human Subjects ◽  
Reaction Force ◽  
Qualitative Change ◽  
Ground Contact ◽  
Moment Arm ◽  
Running Speed ◽  
Ankle Moment ◽  
Quantitative Evidence

Abstract The human foot–ankle complex uses heel-to-toe ground contact progression in walking, but primarily forefoot contact in high-speed running. This qualitative change in ankle control is clear to the runner, but current measures of ankle behavior cannot isolate the effect, and it is unknown how it changes across moderate speeds. We investigated this dynamic ankle control across a range of walking and running speeds using a new measure, the dynamic mean ankle moment arm (DMAMA): the ratio of sagittal ankle moment impulse to ground reaction force impulse on a single limb. We hypothesized that DMAMA would increase with speed in both walking and running, indicating more forefoot-dominated gait with ground reaction forces more anterior to the ankle. Human subjects walked (1.0–2.0 m/s) and ran (2.25–5.25 m/s) on an instrumented treadmill with motion capture and pressure insoles to estimate DMAMA. DMAMA decreased with increasing walking speed, then increased upon the transition to running, and increased further with increasing running speed. These results provide quantitative evidence that walking becomes more hindfoot-dominated as speed increases—similar to behavior during acceleration—and that running is more forefoot-dominated than walking. The instantaneous center of pressure (COP) at initial ground contact did not follow the same trends. The discrepancy highlights the value of DMAMA in summarizing ankle control across the whole stance phase. DMAMA may provide a useful outcome metric for evaluating biomimetic prostheses and for quantifying foot contact styles in running.

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

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0242215
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

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.

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

2020 ◽  
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.

scholarly journals Humanoid standing control: learning from human demonstration

2002 ◽  
Vol 12 (1) ◽  
pp. 16-22 ◽  
Author(s):  
Andreas Hofmann ◽  
Marko Popovic ◽  
Hugh Herr
Keyword(s):  
Ground Reaction Force ◽  
Center Of Pressure ◽  
Human Subjects ◽  
Reaction Force ◽  
Morphological Data ◽  
Human Model ◽  
Joint Torques ◽  
Double Support ◽  
High Level ◽  
Force Data

A three-dimensional numerical model of human standing is presented that reproduces the dynamics of simple swaying motions while in double-support. The human model is structurally realistic, having both trunk and two legs with segment lengths and mass distributions defined using human morphological data from the literature. In this investigation, model stability in standing is achieved through the application of a high-level reduced-order control system where stabilizing forces are applied to the model's trunk by virtual spring- damper elements. To achieve biologically realistic model dynamics, torso position and ground reaction force data measured on human subjects are used as demonstration data in a supervised learning strategy. Using Powell's method, the error between simulation data and measured human data is minimized by varying the virtual high-level force field. Once optimized, the model is shown to track torso position and ground reaction force data from human demonstrations. With only these limited demonstration data, the humanoid model sways in a biologically realistic manner. The model also reproduces the center-of-pressure trajectory beneath the foot, even though no error term for this is included in the optimization algorithm. This indicates that the error terms used (the ones for torso position and ground reaction force) are sufficient to compute the correct joint torques such that independent metrics, like center-of-pressure trajectory, are correct.

A Robotic Ankle–Foot Prosthesis With Active Alignment

2016 ◽  
Vol 10 (2) ◽  
Author(s):  
Andrew Kennedy LaPrè ◽  
Brian R. Umberger ◽  
Frank C. Sup
Keyword(s):  
Center Of Pressure ◽  
Reaction Force ◽  
Residual Limb ◽  
Moment Arm ◽  
Ankle Prosthesis ◽  
Socket Connection ◽  
The Moment ◽  
Socket Interface ◽  
Configuration Changes ◽  
Large Moment

An ankle–foot prosthesis designed to mimic the missing physiological limb generates a large sagittal moment during push off which must be transferred to the residual limb through the socket connection. The large moment is correlated with high internal socket pressures that are often a source of discomfort for the person with amputation, limiting prosthesis use. In this paper, the concept of active alignment is developed. Active alignment realigns the affected residual limb toward the center of pressure (CoP) during stance. During gait, the prosthesis configuration changes to shorten the moment arm between the ground reaction force (GRF) and the residual limb. This reduces the peak moment transferred through the socket interface during late stance. A tethered robotic ankle prosthesis has been developed, and evaluation results are presented for active alignment during normal walking in a laboratory setting. Preliminary testing was performed with a subject without amputation walking with able-bodied adapters at a constant speed. The results show a 33% reduction in the peak resultant moment transferred at the socket limb interface.

scholarly journals Evaluation of a Kinematically-Driven Finite Element Footstrike Model

2016 ◽  
Vol 32 (3) ◽  
pp. 301-305 ◽  
Author(s):  
Iain Hannah ◽  
Andy Harland ◽  
Dan Price ◽  
Heiko Schlarb ◽  
Tim Lucas
Keyword(s):  
Finite Element ◽  
High Speed ◽  
Center Of Pressure ◽  
Reaction Force ◽  
Element Model ◽  
Mechanical Tests ◽  
Vertical Ground Reaction Force ◽  
Dynamic Finite Element ◽  
Tetrahedral Elements ◽  
Vertical Ground

A dynamic finite element model of a shod running footstrike was developed and driven with 6 degree of freedom foot segment kinematics determined from a motion capture running trial. Quadratic tetrahedral elements were used to mesh the footwear components with material models determined from appropriate mechanical tests. Model outputs were compared with experimental high-speed video (HSV) footage, vertical ground reaction force (GRF), and center of pressure (COP) excursion to determine whether such an approach is appropriate for the development of athletic footwear. Although unquantified, good visual agreement to the HSV footage was observed but significant discrepancies were found between the model and experimental GRF and COP readings (9% and 61% of model readings outside of the mean experimental reading ± 2 standard deviations, respectively). Model output was also found to be highly sensitive to input kinematics with a 120% increase in maximum GRF observed when translating the force platform 2 mm vertically. While representing an alternative approach to existing dynamic finite element footstrike models, loading highly representative of an experimental trial was not found to be achievable when employing exclusively kinematic boundary conditions. This significantly limits the usefulness of employing such an approach in the footwear development process.

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

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.

scholarly journals Development of a Subject-Specific Foot-Ground Contact Model for Walking

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Jennifer N. Jackson ◽  
Chris J. Hass ◽  
Benjamin J. Fregly
Keyword(s):  
Center Of Pressure ◽  
Reaction Force ◽  
Walking Ability ◽  
Vertical Force ◽  
Ground Contact ◽  
Contact Pattern ◽  
Flexion Extension ◽  
Subject Specific ◽  
Contact Models ◽  
Force Components

Computational walking simulations could facilitate the development of improved treatments for clinical conditions affecting walking ability. Since an effective treatment is likely to change a patient's foot-ground contact pattern and timing, such simulations should ideally utilize deformable foot-ground contact models tailored to the patient's foot anatomy and footwear. However, no study has reported a deformable modeling approach that can reproduce all six ground reaction quantities (expressed as three reaction force components, two center of pressure (CoP) coordinates, and a free reaction moment) for an individual subject during walking. This study proposes such an approach for use in predictive optimizations of walking. To minimize complexity, we modeled each foot as two rigid segments—a hindfoot (HF) segment and a forefoot (FF) segment—connected by a pin joint representing the toes flexion–extension axis. Ground reaction forces (GRFs) and moments acting on each segment were generated by a grid of linear springs with nonlinear damping and Coulomb friction spread across the bottom of each segment. The stiffness and damping of each spring and common friction parameter values for all springs were calibrated for both feet simultaneously via a novel three-stage optimization process that used motion capture and ground reaction data collected from a single walking trial. The sequential three-stage process involved matching (1) the vertical force component, (2) all three force components, and finally (3) all six ground reaction quantities. The calibrated model was tested using four additional walking trials excluded from calibration. With only small changes in input kinematics, the calibrated model reproduced all six ground reaction quantities closely (root mean square (RMS) errors less than 13 N for all three forces, 25 mm for anterior–posterior (AP) CoP, 8 mm for medial–lateral (ML) CoP, and 2 N·m for the free moment) for both feet in all walking trials. The largest errors in AP CoP occurred at the beginning and end of stance phase when the vertical ground reaction force (vGRF) was small. Subject-specific deformable foot-ground contact models created using this approach should enable changes in foot-ground contact pattern to be predicted accurately by gait optimization studies, which may lead to improvements in personalized rehabilitation medicine.

A Hub Dynamometer for Measurement of Wheel Forces in Off-Road Bicycling

1999 ◽  
Vol 121 (1) ◽  
pp. 132-137 ◽  
Author(s):  
D. S. De Lorenzo ◽  
M. L. Hull
Keyword(s):  
Measurement Errors ◽  
Center Of Pressure ◽  
Reaction Force ◽  
Front Wheel ◽  
Full Scale ◽  
Contact Forces ◽  
Ground Contact ◽  
Strain Gages ◽  
Accuracy Check ◽  
Force Components

A dynamometric hubset that measures the two ground contact force components acting on a bicycle wheel in the plane of the bicycle during off-road riding while either coasting or braking was designed, constructed, and evaluated. To maintain compatibility with standard mountain bike construction, the hubs use commercially available shells with modified, strain gage-equipped axles. The axle strain gages are sensitive to forces acting in the radial and tangential directions, while minimizing sensitivity to transverse forces, steering moments, and variations in the lateral location of the center of pressure. Static calibration and a subsequent accuracy check that computed differences between applied and apparent loads developed during coasting revealed root mean squared errors of 1 percent full-scale or less (full-scale load = 4500 N). The natural frequency of the rear hub with the wheel attached exceeded 350 Hz. These performance capabilities make the dynamometer useful for its intended purpose during coasting. To demonstrate this usefulness, sample ground contact forces are presented for a subject who coasted downhill over rough terrain. The dynamometric hubset can also be used to determine ground contact forces during braking providing that the brake reaction force components are known. However, compliance of the fork can lead to high cross-sensitivity and corresponding large (>5 percent FS) measurement errors at the front wheel.

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

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.

COMPARISON OF ANKLE JOINT LOAD IN DIFFERENT FOOT STRIKE STRATEGIES DURING STAIR ASCENT

2019 ◽  
Vol 19 (07) ◽  
pp. 1940043
Author(s):  
EUI BUM CHOI ◽  
HYEONG MIN JEON ◽  
JAE HOON HEO ◽  
GWANG MOON EOM
Keyword(s):  
Ankle Joint ◽  
Ground Reaction Force ◽  
Center Of Pressure ◽  
Reaction Force ◽  
Moment Arm ◽  
Joint Reaction Force ◽  
Stair Ascent ◽  
Foot Strike ◽  
Joint Load ◽  
Weight Acceptance

The purpose of this study was to find a foot strike strategy that can reduce the ankle joint load during stair ascent by comparing the ankle joint load in two strategies of initial contact during stair ascent. Twenty young subjects performed ascending stairs with two strategies, i.e., rearfoot strike (RFS) and forefoot strike (FFS). Kinematic data was measured from 12 cameras and the ground reaction force was measured by a force plate inserted in the second step of four-step stairs. Stance phase was divided into three phase, i.e., weight acceptance, pull up, and forward continuance. Four ankle related kinetic variables were derived from the measured data, i.e., joint reaction force, moment, and the magnitude and moment arm of ground reaction force. Root-mean-square (RMS) was used as the representative value of the variables during each phase was compared between strategies. In the weight acceptance phase, FFS resulted in greater values of all four kinetic variables than RFS. For the pull-up and forward continuance phases, joint reaction force and ground reaction force were not different between strategies but joint moment and moment arm was greater for FFS than RFS. In weight acceptance phase, greater ground reaction forces and longer moment arm of FFS may have resulted from faster weight transfer to the ipsilateral foot and the more anterior location of center of pressure, respectively. Both have contributed greater joint moment of FFS. In pull-up and forward continuance phases, greater ankle moment of FFS was affected mainly by longer moment arms, which may reflect the persistent farther location of center of pressure from the ankle joint. The results suggest that RFS would be more advantageous than FFS in terms of ankle joint load.

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