Preferred step frequency minimizes veering during natural human walking

Human gait adaptation implies that the nervous system senses energetic cost, yet this signal is unknown. We tested the hypothesis that the blood gas receptors sense cost for gait optimization by controlling blood O2 and CO2 with step frequency as people walked. At the simulated energetic minimum, ventilation and perceived exertion were lowest, yet subjects preferred walking at their original frequency. This suggests that blood gas receptors are not critical for sensing cost during gait.

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Actuated Dual-Slip Model of Planar Slope Walking

Volume 5A: 43rd Mechanisms and Robotics Conference ◽

10.1115/detc2019-97601 ◽

2019 ◽

Author(s):

Raul Lema Galindo ◽

Elise Weimholt ◽

James P. Schmiedeler

Keyword(s):

Step Length ◽

Model Complexity ◽

Human Walking ◽

Slip Model ◽

Step Frequency ◽

Speed Range ◽

Planar Slope ◽

Actuation Scheme ◽

Future Work ◽

Flat Ground

Abstract The planar dual spring-loaded inverted pendulum (dual-SLIP) model is a well-established passive template of human walking on flat ground. This paper applies an actuated extension of the model to walking on inclines and declines to evaluate how well it captures the behavior observed in human slope walking. The motivation is to apply the template to improve control of humanoid robot walking and/or intent detection in exoskeleton-assisted walking. Gaits of the actuated planar dual-SLIP model are found via the solution of a constrained nonlinear optimization problem in ten parameters. The majority of those parameters define the actuation scheme that injects energy for incline walking and absorbs energy for decline walking to achieve periodic, nonconservative gaits. Solution gaits across the speed range of 1.0 to 1.6 ms and slope range of −10 to 10 degrees exhibit some of the characteristics of human walking, such as the effect of slope on stance duration, step frequency, and step length. Efforts to reduce the number of parameters optimized by enforcing relationships observed in the solution gaits proved unsuccessful, suggesting that future work must trade off model complexity with fidelity of representation of human behavior.

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Increasing the gradient of energetic cost does not initiate adaptation in human walking

Journal of Neurophysiology ◽

10.1152/jn.00311.2020 ◽

2021 ◽

Author(s):

Surabhi N Simha ◽

Jeremy D. Wong ◽

Jessica C Selinger ◽

Sabrina J Abram ◽

J. Maxwell Donelan

Keyword(s):

Nervous System ◽

Lower Cost ◽

Cost Savings ◽

Control Policy ◽

Human Walking ◽

Energetic Cost ◽

Mechatronic System ◽

Step Frequency ◽

Normalized Units ◽

New Situation

When in a new situation, the nervous system may benefit from adapting its control policy. In determining whether or not to initiate this adaptation, the nervous system may rely on some features of the new situation. Here we tested whether one such feature is salient cost savings. We changed cost saliency by manipulating the gradient of participants' energetic cost landscape during walking. We hypothesized that steeper gradients would cause participants to spontaneously adapt their step frequency to lower costs. To manipulate the gradient, a mechatronic system applied controlled fore-aft forces to the waist of participants as a function of their step frequency as they walked on a treadmill. These forces increased the energetic cost of walking at high step frequencies and reduced it at low step frequencies. We successfully created three cost landscapes of increasing gradients, where the natural variability in participants' step frequency provided cost changes of 3.6% (shallow), 7.2% (intermediate) and 10.2% (steep). Participants did not spontaneously initiate adaptation in response to any of the gradients. Using metronome-guided walking-a previously established protocol for eliciting initiation of adaptation-participants next experienced a step frequency with a lower cost. Participants then adapted by -1.41±0.81 (p=0.007) normalized units away from their originally preferred step frequency obtaining cost savings of 4.80±3.12% That participants would adapt under some conditions, but not in response to steeper cost gradients, suggests that the nervous system does not solely rely on the gradient of energetic cost to initiate adaptation in novel situations.

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A mechatronic system for studying energy optimization during walking.

10.1101/496489 ◽

2018 ◽

Cited By ~ 1

Author(s):

Surabhi N Simha ◽

J. Maxwell Donelan

Keyword(s):

Nervous System ◽

System Design ◽

Human Movement ◽

Human Walking ◽

Energetic Cost ◽

Mechatronic System ◽

Step Frequency ◽

Coordination Strategies ◽

Design Build ◽

Optimal Coordination

A general principle of human movement is that our nervous system is able to learn optimal coordination strategies. However, how our nervous system performs this optimization is not well understood. Here we design, build, and test a mechatronic system to probe the algorithms underlying optimization of energetic cost in walking. The system applies controlled fore-aft forces to a hip-belt worn by a user, decreasing their energetic cost by pulling forward or increasing it by pulling backward. The system controls the forces, and thus energetic cost, as a function of how the user is moving. In testing, we found that the system can quickly, accurately, and precisely apply target forces within a walking step. We next controlled the forces as a function of the user's step frequency and found that we could predictably reshape their energetic cost landscape. Finally, we tested whether users adapted their walking in response to the new cost landscapes created by our system, and found that users shifted their step frequency towards the new energetic minima. Our system design appears to be effective for reshaping energetic cost landscapes in human walking to study how the nervous system optimizes movement.

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Effects of pole compliance and step frequency on the biomechanics and economy of pole carrying during human walking

Journal of Applied Physiology ◽

10.1152/japplphysiol.00119.2014 ◽

2014 ◽

Vol 117 (5) ◽

pp. 507-517 ◽

Cited By ~ 16

Author(s):

Eric R. Castillo ◽

Graham M. Lieberman ◽

Logan S. McCarty ◽

Daniel E. Lieberman

Keyword(s):

Oxygen Consumption ◽

Harmonic Oscillator ◽

Natural Frequency ◽

Human Walking ◽

Step Frequency ◽

Damped Harmonic Oscillator ◽

Save Energy ◽

Centers Of Mass ◽

Pole System ◽

Equal Amplitude

This study investigates whether a flexible pole can be used as an energy-saving method for humans carrying loads. We model the carrier and pole system as a driven damped harmonic oscillator and predict that the energy expended by the carrier is affected by the compliance of the pole and the ratio between the pole's natural frequency and the carrier's step frequency. We tested the model by measuring oxygen consumption in 16 previously untrained male participants walking on a treadmill at four step frequencies using two loaded poles: one made of bamboo and one of steel. We found that when the bamboo pole was carried at a step frequency 20% greater than its natural frequency, the motions of the centers of mass of the load and carrier were approximately equal in amplitude and opposite in phase, which we predicted would save energy for the carrier. Carrying the steel pole, however, resulted in the carrier and loads oscillating in phase and with roughly equal amplitude. Although participants were less economical using poles than predicted costs using conventional fixed-load techniques (such as backpacks), the bamboo pole was on average 5.0% less costly than the steel pole. When allowed to select their cadence, participants also preferred to carry the bamboo pole at step frequencies of ∼2.0 Hz. This frequency, which is significantly higher than the preferred unloaded step frequency, is most economical. These experiments suggest that pole carriers can intuitively adjust their gaits, or choose poles with appropriate compliance, to increase energetic savings.

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Increasing the gradient of energetic cost does not initiate adaptation in human walking

10.1101/2020.05.20.107250 ◽

2020 ◽

Author(s):

Surabhi N. Simha ◽

Jeremy D. Wong ◽

Jessica C. Selinger ◽

Sabrina J. Abram ◽

J. Maxwell Donelan

Keyword(s):

Nervous System ◽

Lower Cost ◽

Cost Savings ◽

Control Policy ◽

Human Walking ◽

Energetic Cost ◽

Mechatronic System ◽

Step Frequency ◽

Normalized Units ◽

New Situation

AbstractWhen in a new situation, the nervous system may benefit from adapting its control policy. In determining whether or not to initiate this adaptation, the nervous system may rely on some features of the new situation. Here we tested whether one such feature is salient cost savings. We changed cost saliency by manipulating the gradient of participants’ energetic cost landscape during walking. We hypothesized that steeper gradients would cause participants to spontaneously adapt their step frequency to lower costs. To manipulate the gradient, a mechatronic system applied controlled fore-aft forces to the waist of participants as a function of their step frequency as they walked on a treadmill. These forces increased the energetic cost of walking at high step frequencies and reduced it at low step frequencies. We successfully created three cost landscapes of increasing gradients, where the natural variability in participants’ step frequency provided cost changes of 3.6% (shallow), 7.2% (intermediate) and 10.2% (steep). Participants did not spontaneously initiate adaptation in response to any of the gradients. Using metronome-guided walking— a previously established protocol for eliciting initiation of adaptation—participants next experienced a step frequency with a lower cost. Participants then adapted by −1.41±0.81 (p=0.007) normalized units away from their originally preferred step frequency obtaining cost savings of 4.80±3.12%. That participants would adapt under some conditions, but not in response to steeper cost gradients, suggests that the nervous system does not solely rely on the gradient of energetic cost to initiate adaptation in novel situations.

Download Full-text