Non‐Steady Locomotion

Daley, Monica A.

doi:10.1002/9781119113713.ch11

Cited by 11 publications

(9 citation statements)

References 92 publications

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“…Namely, we considered what happens in the space of muscle synergies when humans switch from walking to running, from overground to treadmill locomotion, from unperturbed to perturbed locomotion, and in aging. We chose these conditions to compare different challenges or constraints to locomotion: running allows less time for organizing coordinated movements than walking ; externally perturbed locomotion is more challenging than unperturbed locomotion due to the increased mechanical and physiological limits imposed by the higher environmental complexity (Daley, 2016;; aging is a source of internal perturbation that leads to muscle weakness and loss of fine neural control at various levels (e.g., CNS, proprioceptive, etc.) (Monaco et al, 2010;Nutt et al, 1993).…”

Section: Introductionmentioning

confidence: 99%

Neuromotor Dynamics of Human Locomotion in Challenging Settings

et al. 2020

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Is the control of movement less stable when we walk or run in challenging settings? Intuitively, one might answer that it is, given that challenging locomotion externally (e.g., rough terrain) or internally (e.g., age-related impairments) makes our movements more unstable. Here, we investigated how young and old humans synergistically activate muscles during locomotion when different perturbation levels are introduced. Of these control signals, called muscle synergies, we analyzed the local stability and the complexity (or irregularity) over time. Surprisingly, we found that perturbations force the central nervous system to produce muscle activation patterns that are less unstable and less complex. These outcomes show that robust locomotion control in challenging settings is achieved by producing less complex control signals that are more stable over time, whereas easier tasks allow for more unstable and irregular control.

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Section: Introductionmentioning

confidence: 99%

Neuromotor Dynamics of Human Locomotion in Challenging Settings

et al. 2020

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“…Namely, we considered what happens in the space of muscle synergies when humans switch from walking to running, from overground to treadmill locomotion, from unperturbed to perturbed locomotion and in aging. We chose these conditions to compare different kinds of constraints on locomotion: running allows less time for organizing coordinated 25 movements than walking (20); externally-perturbed locomotion is more constrained than unperturbed due to the increased mechanical and physiological limits imposed by the higher environmental complexity (7,21); aging is a source of internal perturbation which leads to muscle weakness and loss of fine neural control at various levels (e.g. CNS, proprioceptive, etc.)…”

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confidence: 99%

Humans exploit robust locomotion by improving the stability of control signals

Santuz

Brüll

Ekizos

et al. 2019

Preprint

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Is the control of movement less stable when we walk or run in challenging settings? One might intuitively answer affirmatively, given that adding constraints to locomotion (e.g. rough terrain, age-related impairments, etc.) imply less stable movements. We investigated how young and old humans synergistically activate muscles during locomotion, when different perturbation levels 20 are introduced. Of these control signals, called muscle synergies, we then analyzed the stability over time. Surprisingly, we found that perturbations and older age force the central nervous system to produce more stable signals. These outcomes show that robust locomotion in challenging settings is achieved by increasing the stability of control signals, whereas easier tasks allow for more unstable control. 25

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“…Legged locomotion is complex and dynamic, involving abrupt foot-contact transitions and uncertainty due to variable terrain and sensorimotor errors. Animals must precisely control limb dynamics to move effectively over varied and uncertain terrain while avoiding falls, collisions, and injury ( Daley 2016 ). It remains poorly understood how the sensory, neural, and mechanical components of control are integrated to achieve robust, stable, and agile locomotion.…”

Section: What Are the Challenges In Achieving Agile Bipedal Locomotiomentioning

confidence: 99%

“…It remains poorly understood how the sensory, neural, and mechanical components of control are integrated to achieve robust, stable, and agile locomotion. Here, robustness refers to how large a disturbance an animal can tolerate while still meeting the functional demands of the task, such as forward movement at an acceptable speed ( Daley 2016 ). Disturbances can arise externally from the environment, internally from sensorimotor noise (such as errors in motor commands), or from inaccurate sensory information (such as lack of visibility or conflict between sensory modalities).…”

Section: What Are the Challenges In Achieving Agile Bipedal Locomotiomentioning

confidence: 99%

“…Disturbances can arise externally from the environment, internally from sensorimotor noise (such as errors in motor commands), or from inaccurate sensory information (such as lack of visibility or conflict between sensory modalities). Stability quantifies how rapidly the system attenuates perturbations from steady-state locomotion, and agility refers to the ability to rapidly adjust locomotor dynamics to meet changing task demands (such as a rapid extension of the leg to leap over an obstacle) ( Daley 2016 ; Duperret et al. 2016 ).…”

Section: What Are the Challenges In Achieving Agile Bipedal Locomotiomentioning

confidence: 99%

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Understanding the agility of running birds: Sensorimotor and mechanical factors in avian bipedal locomotion

Daley

2018

Integrative and Comparative Biology

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Birds are a diverse and agile lineage of vertebrates that all use bipedal locomotion for at least part of their life. Thus birds provide a valuable opportunity to investigate how biomechanics and sensorimotor control are integrated for agile bipedal locomotion. This review summarizes recent work using terrain perturbations to reveal neuromechanical control strategies used by ground birds to achieve robust, stable, and agile running. Early experiments in running guinea fowl aimed to reveal the immediate intrinsic mechanical response to an unexpected drop (“pothole”) in terrain. When navigating the pothole, guinea fowl experience large changes in leg posture in the perturbed step, which correlates strongly with leg loading and perturbation recovery. Analysis of simple theoretical models of running has further confirmed the crucial role of swing-leg trajectory control for regulating foot contact timing and leg loading in uneven terrain. Coupling between body and leg dynamics results in an inherent trade-off in swing leg retraction rate for fall avoidance versus injury avoidance. Fast leg retraction minimizes injury risk, but slow leg retraction minimizes fall risk. Subsequent experiments have investigated how birds optimize their control strategies depending on the type of perturbation (pothole, step, obstacle), visibility of terrain, and with ample practice negotiating terrain features. Birds use several control strategies consistently across terrain contexts: (1) independent control of leg angular cycling and leg length actuation, which facilitates dynamic stability through simple control mechanisms, (2) feedforward regulation of leg cycling rate, which tunes foot-contact timing to maintain consistent leg loading in uneven terrain (minimizing fall and injury risks), (3) load-dependent muscle actuation, which rapidly adjusts stance push-off and stabilizes body mechanical energy, and (4) multi-step recovery strategies that allow body dynamics to transiently vary while tightly regulating leg loading to minimize risks of fall and injury. In future work, it will be interesting to investigate the learning and adaptation processes that allow animals to adjust neuromechanical control mechanisms over short and long timescales.

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Non‐Steady Locomotion

Cited by 11 publications

References 92 publications

Neuromotor Dynamics of Human Locomotion in Challenging Settings

Neuromotor Dynamics of Human Locomotion in Challenging Settings

Humans exploit robust locomotion by improving the stability of control signals

Understanding the agility of running birds: Sensorimotor and mechanical factors in avian bipedal locomotion

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