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Koginov G, Wolf P, Schmidt K, Duarte JE, Riener R. Guided Exploration Leads to Faster Familiarization with a Wearable Robot: First Results of an Innovative Protocol. IEEE Int Conf Rehabil Robot 2023; 2023:1-6. [PMID: 37941259 DOI: 10.1109/icorr58425.2023.10304725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2023]
Abstract
Wearable robots show promise in addressing physical and functional deficits in individuals with mobility impairments. However, the process of learning to use these devices can take a long time. In this study, we propose a novel protocol to support the familiarization process with a wearable robot (the Myosuit) and achieve faster walking speeds. The protocol involves applying an anterior pulling force while participants perform a series of 10-meter Walking Tests (10mWT) with or without the Myosuit under various experimental conditions. We hypothesized that guiding the exploration of novel walking patterns can help the users learn to exploit the Myosuit's assistance faster by leading to larger step lengths and ultimately higher walking speeds. In this paper, we present the preliminary results of the protocol with seven participants with lower-limb mobility impairments. Participants who were assisted by the Myosuit showed a continuous increase in walking speed over the course of the pulling part of the experiment with a maximum increase of 41.3% (10.4%) when compared to the baseline 10mWT. Following the removal of the pulling force, these participants continued to show an increased walking speed while being supported by the Myosuit. This higher walking speed was primarily due to a significant increase in step length of 24% (16.6%) and cadence of 11% (8.9%). The results of this study may help the development of familiarization techniques for wearable robots.
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Mulla DM, Keir PJ. Neuromuscular control: from a biomechanist's perspective. Front Sports Act Living 2023; 5:1217009. [PMID: 37476161 PMCID: PMC10355330 DOI: 10.3389/fspor.2023.1217009] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 06/21/2023] [Indexed: 07/22/2023] Open
Abstract
Understanding neural control of movement necessitates a collaborative approach between many disciplines, including biomechanics, neuroscience, and motor control. Biomechanics grounds us to the laws of physics that our musculoskeletal system must obey. Neuroscience reveals the inner workings of our nervous system that functions to control our body. Motor control investigates the coordinated motor behaviours we display when interacting with our environment. The combined efforts across the many disciplines aimed at understanding human movement has resulted in a rich and rapidly growing body of literature overflowing with theories, models, and experimental paradigms. As a result, gathering knowledge and drawing connections between the overlapping but seemingly disparate fields can be an overwhelming endeavour. This review paper evolved as a need for us to learn of the diverse perspectives underlying current understanding of neuromuscular control. The purpose of our review paper is to integrate ideas from biomechanics, neuroscience, and motor control to better understand how we voluntarily control our muscles. As biomechanists, we approach this paper starting from a biomechanical modelling framework. We first define the theoretical solutions (i.e., muscle activity patterns) that an individual could feasibly use to complete a motor task. The theoretical solutions will be compared to experimental findings and reveal that individuals display structured muscle activity patterns that do not span the entire theoretical solution space. Prevalent neuromuscular control theories will be discussed in length, highlighting optimality, probabilistic principles, and neuromechanical constraints, that may guide individuals to families of muscle activity solutions within what is theoretically possible. Our intention is for this paper to serve as a primer for the neuromuscular control scientific community by introducing and integrating many of the ideas common across disciplines today, as well as inspire future work to improve the representation of neural control in biomechanical models.
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Krajewski KT, Johnson CC, Ahamed NU, Moir GL, Mi Q, Flanagan SD, Anderst WJ, Connaboy C. Recruit-aged adults may preferentially weight task goals over deleterious cost functions during short duration loaded and imposed gait tasks. Sci Rep 2023; 13:4910. [PMID: 36966216 PMCID: PMC10039906 DOI: 10.1038/s41598-023-31972-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Accepted: 03/20/2023] [Indexed: 03/27/2023] Open
Abstract
Optimal motor control that is stable and adaptable to perturbation is reflected in the temporal arrangement and regulation of gait variability. Load carriage and forced-marching are common military relevant perturbations to gait that have been implicated in the high incidence of musculoskeletal injuries in military populations. We investigated the interactive effects of load magnitude and locomotion pattern on motor variability, stride regulation and spatiotemporal complexity during gait in recruit-aged adults. We further investigated the influences of sex and task duration. Healthy adults executed trials of running and forced-marching with and without loads at 10% above their gait transition velocity. Spatiotemporal parameters were analyzed using a goal equivalent manifold approach. With load and forced-marching, individuals used a greater array of motor solutions to execute the task goal (maintain velocity). Stride-to-stride regulation became stricter as the task progressed. Participants exhibited optimal spatiotemporal complexity with significant but not meaningful differences between sexes. With the introduction of load carriage and forced-marching, individuals relied on a strategy that maximizes and regulates motor solutions that achieve the task goal of velocity specifically but compete with other task functions. The appended cost penalties may have deleterious effects during prolonged execution, potentially increasing the risk of musculoskeletal injuries.
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Affiliation(s)
- Kellen T Krajewski
- Department of Sports Medicine and Nutrition, University of Pittsburgh, Pittsburgh, PA, USA.
| | - Camille C Johnson
- Biodynamics Laboratory, Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA
| | - Nizam U Ahamed
- Department of Sports Medicine and Nutrition, University of Pittsburgh, Pittsburgh, PA, USA
| | - Gavin L Moir
- Exercise Science Department, East Stroudsburg University, East Stroudsburg, PA, USA
| | - Qi Mi
- Department of Sports Medicine and Nutrition, University of Pittsburgh, Pittsburgh, PA, USA
| | - Shawn D Flanagan
- Department of Sports Medicine and Nutrition, University of Pittsburgh, Pittsburgh, PA, USA
| | - William J Anderst
- Biodynamics Laboratory, Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA
| | - Chris Connaboy
- Department of Sports Medicine and Nutrition, University of Pittsburgh, Pittsburgh, PA, USA
- Center for Lower Extremity Ambulatory Research, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA
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Buisseret F, Dehouck V, Boulanger N, Henry G, Piccinin F, White O, Dierick F. Adiabatic Invariant of Center-of-Mass Motion during Walking as a Dynamical Stability Constraint on Stride Interval Variability and Predictability. BIOLOGY 2022; 11:biology11091334. [PMID: 36138813 PMCID: PMC9495666 DOI: 10.3390/biology11091334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Revised: 09/06/2022] [Accepted: 09/07/2022] [Indexed: 11/16/2022]
Abstract
Simple Summary Human walking exhibits properties of both stability and variability. On the one hand, the variability of the interval of time between heel strikes is autocorrelated, i.e., not randomly organized. On the other hand, walking is highly stereotyped and arguments from general mechanics suggest that the stability of gait can be assessed according to invariant properties. This study aims at proposing one of those invariants. Participants walked for 10 min at a natural pace, with and without a metronome indicating participants’ preferred step frequency. In both cases, we use different parameters to assess both the variability and stability of walking. We verify a known result: the metronome strongly alters the variability of the motion. However, despite the large variability changes, our proposed adiabatic invariant is preserved in both conditions, demonstrating the stability of gait. It appears as though our model reveals dynamical constraints that are “hidden” beyond apparent walking variability. Abstract Human walking exhibits properties of global stability, and local dynamic variability, predictability, and complexity. Global stability is typically assessed by quantifying the whole-body center-of-mass motion while local dynamic variability, predictability, and complexity are assessed using the stride interval. Recent arguments from general mechanics suggest that the global stability of gait can be assessed with adiabatic invariants, i.e., quantities that remain approximately constant, even under slow external changes. Twenty-five young healthy participants walked for 10 min at a comfortable pace, with and without a metronome indicating preferred step frequency. Stride interval variability was assessed by computing the coefficient of variation, predictability using the Hurst exponent, and complexity via the fractal dimension and sample entropy. Global stability of gait was assessed using the adiabatic invariant computed from averaged kinetic energy value related to whole-body center-of-mass vertical displacement. We show that the metronome alters the stride interval variability and predictability, from autocorrelated dynamics to almost random dynamics. However, despite these large local variability and predictability changes, the adiabatic invariant is preserved in both conditions, showing the global stability of gait. Thus, the adiabatic invariant theory reveals dynamical global stability constraints that are “hidden” behind apparent local walking variability and predictability.
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Affiliation(s)
- Fabien Buisseret
- CeREF-Technique, Chaussée de Binche 159, 7000 Mons, Belgium
- Forme and Fonctionnement Humain Laboratory, Department of Physical Therapy, Haute Ecole Louvain en Hainaut, rue Trieu Kaisin 136, 6061 Montignies-sur-Sambre, Belgium
- Service de Physique Nucléaire et Subnucléaire, UMONS Research Institute for Complex Systems, Université de Mons, 20 Place du Parc, 7000 Mons, Belgium
- Correspondence:
| | - Victor Dehouck
- Service de Physique de l’Univers, Champs et Gravitation, UMONS Research Institute for Complex Systems, Université de Mons, 20 Place du Parc, 7000 Mons, Belgium
- Cognition, Action et Plasticité Sensorimotrice (CAPS), INSERM UMR1093, UFR STAPS, Université de Bourgogne Franche-Comté, BP 27877, 21078 Dijon, France
| | - Nicolas Boulanger
- Service de Physique de l’Univers, Champs et Gravitation, UMONS Research Institute for Complex Systems, Université de Mons, 20 Place du Parc, 7000 Mons, Belgium
| | - Guillaume Henry
- Forme and Fonctionnement Humain Laboratory, Department of Physical Therapy, Haute Ecole Louvain en Hainaut, rue Trieu Kaisin 136, 6061 Montignies-sur-Sambre, Belgium
| | - Florence Piccinin
- Forme and Fonctionnement Humain Laboratory, Department of Physical Therapy, Haute Ecole Louvain en Hainaut, rue Trieu Kaisin 136, 6061 Montignies-sur-Sambre, Belgium
| | - Olivier White
- Cognition, Action et Plasticité Sensorimotrice (CAPS), INSERM UMR1093, UFR STAPS, Université de Bourgogne Franche-Comté, BP 27877, 21078 Dijon, France
| | - Frédéric Dierick
- CeREF-Technique, Chaussée de Binche 159, 7000 Mons, Belgium
- Laboratoire d’Analyse du Mouvement et de la Posture (LAMP), Centre National de Rééducation Fonctionnelle et de Réadaptation—Rehazenter, Rue André Vésale 1, 2674 Luxembourg, Luxembourg
- Faculté des Sciences de la Motricité, UCLouvain, Place Pierre de Coubertin 2, 1348 Louvain-la-Neuve, Belgium
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Roemmich RT, Bastian AJ. Motor control: In constant pursuit of optimality. Curr Biol 2022; 32:R462-R463. [PMID: 35609542 PMCID: PMC10053727 DOI: 10.1016/j.cub.2022.03.058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Humans learn through exploration. A new study suggests that this may be how we learn to save energy when we walk.
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Affiliation(s)
- Ryan T Roemmich
- Hugo W. Moser Research Institute at Kennedy Krieger, 716 North Broadway, Baltimore, MD 21205, USA; Department of Physical Medicine and Rehabilitation, The Johns Hopkins School of Medicine, 600 North Wolfe Street, Baltimore, MD 21287, USA
| | - Amy J Bastian
- Hugo W. Moser Research Institute at Kennedy Krieger, 716 North Broadway, Baltimore, MD 21205, USA; Department of Physical Medicine and Rehabilitation, The Johns Hopkins School of Medicine, 600 North Wolfe Street, Baltimore, MD 21287, USA; Department of Neuroscience, The Johns Hopkins School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA.
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6
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Medrano RL, Thomas GC, Rouse EJ. Can humans perceive the metabolic benefit provided by augmentative exoskeletons? J Neuroeng Rehabil 2022; 19:26. [PMID: 35219335 PMCID: PMC8881941 DOI: 10.1186/s12984-022-01002-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 02/15/2022] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND The purpose of augmentative exoskeletons is to help people exceed the limitations of their human bodies, but this cannot be realized unless people choose to use these exciting technologies. Although human walking efficiency has been highly optimized over generations, exoskeletons have been able to consistently improve this efficiency by 10-15%. However, despite these measurable improvements, exoskeletons today remain confined to the laboratory. To achieve widespread adoption, exoskeletons must not only exceed the efficiency of human walking, but also provide a perceivable benefit to their wearers. METHODS In this study, we quantify the perceptual threshold of the metabolic efficiency benefit provided during exoskeleton-assisted locomotion. Ten participants wore bilateral ankle exoskeletons during continuous walking. The assistance provided by the exoskeletons was varied in 2 min intervals while participants provided feedback on their metabolic rate. These data were aggregated and used to estimate the perceptual threshold. RESULTS Participants were able to detect a change in their metabolic rate of 22.7% (SD: 17.0%) with 75% accuracy. This indicates that in the short term and on average, wearers cannot yet reliably perceive the metabolic benefits of today's augmentative exoskeletons. CONCLUSIONS If wearers cannot perceive the benefits provided by these technologies, it will negatively affect their impact, including long-term adoption and product viability. Future exoskeleton researchers and designers can use these methods and results to inform the development of exoskeletons that reach their potential.
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Affiliation(s)
- Roberto Leo Medrano
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, 48109 USA
- Robotics Institute, University of Michigan, 48109 Ann Arbor, USA
| | - Gray Cortright Thomas
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, 48109 USA
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, 48109 USA
- Robotics Institute, University of Michigan, 48109 Ann Arbor, USA
| | - Elliott J. Rouse
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, 48109 USA
- Robotics Institute, University of Michigan, 48109 Ann Arbor, USA
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McAllister MJ, Blair RL, Donelan JM, Selinger JC. Energy optimization during walking involves implicit processing. J Exp Biol 2021; 224:272119. [PMID: 34521117 DOI: 10.1242/jeb.242655] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Accepted: 08/02/2021] [Indexed: 11/20/2022]
Abstract
Gait adaptations, in response to novel environments, devices or changes to the body, can be driven by the continuous optimization of energy expenditure. However, whether energy optimization involves implicit processing (occurring automatically and with minimal cognitive attention), explicit processing (occurring consciously with an attention-demanding strategy) or both in combination remains unclear. Here, we used a dual-task paradigm to probe the contributions of implicit and explicit processes in energy optimization during walking. To create our primary energy optimization task, we used lower-limb exoskeletons to shift people's energetically optimal step frequency to frequencies lower than normally preferred. Our secondary task, designed to draw explicit attention from the optimization task, was an auditory tone discrimination task. We found that adding this secondary task did not prevent energy optimization during walking; participants in our dual-task experiment adapted their step frequency toward the optima by an amount and at a rate similar to participants in our previous single-task experiment. We also found that performance on the tone discrimination task did not worsen when participants were adapting toward energy optima; accuracy scores and reaction times remained unchanged when the exoskeleton altered the energy optimal gaits. Survey responses suggest that dual-task participants were largely unaware of the changes they made to their gait during adaptation, whereas single-task participants were more aware of their gait changes yet did not leverage this explicit awareness to improve gait adaptation. Collectively, our results suggest that energy optimization involves implicit processing, allowing attentional resources to be directed toward other cognitive and motor objectives during walking.
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Affiliation(s)
| | - Rachel L Blair
- Simon Fraser University, Burnaby, BC, Canada, V5A 1S6.,University of British Columbia, Department of Anesthesiology, Vancouver, BC, Canada, V6T 1Z3
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8
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Evaluating the energetics of entrainment in a human-machine coupled oscillator system. Sci Rep 2021; 11:15804. [PMID: 34349146 PMCID: PMC8338938 DOI: 10.1038/s41598-021-95047-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Accepted: 07/19/2021] [Indexed: 12/03/2022] Open
Abstract
During locomotion, humans sometimes entrain (i.e. synchronize) their steps to external oscillations: e.g. swaying bridges, tandem walking, bouncy harnesses, vibrating treadmills, exoskeletons. Previous studies have discussed the role of nonlinear oscillators (e.g. central pattern generators) in facilitating entrainment. However, the energetics of such interactions are unknown. Given substantial evidence that humans prioritize economy during locomotion, we tested whether reduced metabolic expenditure is associated with human entrainment to vertical force oscillations, where frequency and amplitude were prescribed via a custom mechatronics system during walking. Although metabolic cost was not significantly reduced during entrainment, individuals expended less energy when the oscillation forces did net positive work on the body and roughly selected phase relationships that maximize positive work. It is possible that individuals use mechanical cues to infer energy cost and inform effective gait strategies. If so, an accurate prediction may rely on the relative stability of interactions with the environment. Our results suggest that entrainment occurs over a wide range of oscillation parameters, though not as a direct priority for minimizing metabolic cost. Instead, entrainment may act to stabilize interactions with the environment, thus increasing predictability for the effective implementation of internal models that guide energy minimization.
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Brown GL, Seethapathi N, Srinivasan M. A unified energy-optimality criterion predicts human navigation paths and speeds. Proc Natl Acad Sci U S A 2021; 118:e2020327118. [PMID: 34266945 PMCID: PMC8307777 DOI: 10.1073/pnas.2020327118] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Navigating our physical environment requires changing directions and turning. Despite its ecological importance, we do not have a unified theoretical account of non-straight-line human movement. Here, we present a unified optimality criterion that predicts disparate non-straight-line walking phenomena, with straight-line walking as a special case. We first characterized the metabolic cost of turning, deriving the cost landscape as a function of turning radius and rate. We then generalized this cost landscape to arbitrarily complex trajectories, allowing the velocity direction to deviate from body orientation (holonomic walking). We used this generalized optimality criterion to mathematically predict movement patterns in multiple contexts of varying complexity: walking on prescribed paths, turning in place, navigating an angled corridor, navigating freely with end-point constraints, walking through doors, and navigating around obstacles. In these tasks, humans moved at speeds and paths predicted by our optimality criterion, slowing down to turn and never using sharp turns. We show that the shortest path between two points is, counterintuitively, often not energy-optimal, and, indeed, humans do not use the shortest path in such cases. Thus, we have obtained a unified theoretical account that predicts human walking paths and speeds in diverse contexts. Our model focuses on walking in healthy adults; future work could generalize this model to other human populations, other animals, and other locomotor tasks.
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Affiliation(s)
- Geoffrey L Brown
- Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210
- Feinberg School of Medicine, Northwestern University, Chicago, IL 60611
| | - Nidhi Seethapathi
- Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104
| | - Manoj Srinivasan
- Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210;
- Program in Biophysics, The Ohio State University, Columbus, OH 43210
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10
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Simha SN, Wong JD, Selinger JC, Abram SJ, Donelan JM. Increasing the gradient of energetic cost does not initiate adaptation in human walking. J Neurophysiol 2021; 126:440-450. [PMID: 34161744 DOI: 10.1152/jn.00311.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
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.NEW & NOTEWORTHY People can adapt to novel conditions but often require cues to initiate the adaptation. Using a mechatronic system to reshape energetic cost gradients during treadmill walking, we tested whether the nervous system can use information present in the cost gradient to spontaneously initiate adaptation. We found that our participants did not spontaneously initiate adaptation even in the steepest gradient. The nervous system does not rely solely on the cost gradient when initiating adaptation.
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Affiliation(s)
- Surabhi N Simha
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Jeremy D Wong
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada.,Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Jessica C Selinger
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada.,School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada
| | - Sabrina J Abram
- School of Engineering Science, Simon Fraser University, Burnaby, British Columbia, Canada
| | - J Maxwell Donelan
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
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11
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Unprompted Alteration of Freely Chosen Movement Rate During Stereotyped Rhythmic Movement: Examples and Review. Motor Control 2021; 25:385-402. [PMID: 33883299 DOI: 10.1123/mc.2020-0049] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 01/19/2021] [Accepted: 01/30/2021] [Indexed: 11/18/2022]
Abstract
Investigations of behavior and control of voluntary stereotyped rhythmic movement contribute to the enhancement of motor function and performance of disabled, sick, injured, healthy, and exercising humans. The present article presents examples of unprompted alteration of freely chosen movement rate during voluntary stereotyped rhythmic movements. The examples, in the form of both increases and decreases of movement rate, are taken from activities of cycling, finger tapping, and locomotion. It is described that, for example, strength training, changed power output, repeated bouts, and changed locomotion speed can elicit an unprompted alteration of freely chosen movement rate. The discussion of the examples is based on a tripartite interplay between descending drive, rhythm-generating spinal neural networks, and sensory feedback, as well as terminology from dynamic systems theory.
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Shafer BA, Philius SA, Nuckols RW, McCall J, Young AJ, Sawicki GS. Neuromechanics and Energetics of Walking With an Ankle Exoskeleton Using Neuromuscular-Model Based Control: A Parameter Study. Front Bioeng Biotechnol 2021; 9:615358. [PMID: 33954159 PMCID: PMC8091965 DOI: 10.3389/fbioe.2021.615358] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Accepted: 03/01/2021] [Indexed: 11/13/2022] Open
Abstract
Powered ankle exoskeletons that apply assistive torques with optimized timing and magnitude can reduce metabolic cost by ∼10% compared to normal walking. However, finding individualized optimal control parameters is time consuming and must be done independently for different walking modes (e.g., speeds, slopes). Thus, there is a need for exoskeleton controllers that are capable of continuously adapting torque assistance in concert with changing locomotor demands. One option is to use a biologically inspired, model-based control scheme that can capture the adaptive behavior of the human plantarflexors during natural gait. Here, based on previously demonstrated success in a powered ankle-foot prosthesis, we developed an ankle exoskeleton controller that uses a neuromuscular model (NMM) comprised of a Hill type musculotendon driven by a simple positive force feedback reflex loop. To examine the effects of NMM reflex parameter settings on (i) ankle exoskeleton mechanical performance and (ii) users' physiological response, we recruited nine healthy, young adults to walk on a treadmill at a fixed speed of 1.25 m/s while donning bilateral tethered robotic ankle exoskeletons. To quantify exoskeleton mechanics, we measured exoskeleton torque and power output across a range of NMM controller Gain (0.8-2.0) and Delay (10-40 ms) settings, as well as a High Gain/High Delay (2.0/40 ms) combination. To quantify users' physiological response, we compared joint kinematics and kinetics, ankle muscle electromyography and metabolic rate between powered and unpowered/zero-torque conditions. Increasing NMM controller reflex Gain caused increases in average ankle exoskeleton torque and net power output, while increasing NMM controller reflex Delay caused a decrease in net ankle exoskeleton power output. Despite systematic reduction in users' average biological ankle moment with exoskeleton mechanical assistance, we found no NMM controller Gain or Delay settings that yielded changes in metabolic rate. Post hoc analyses revealed weak association at best between exoskeleton and biological mechanics and changes in users' metabolic rate. Instead, changes in users' summed ankle joint muscle activity with powered assistance correlated with changes in their metabolic energy use, highlighting the potential to utilize muscle electromyography as a target for on-line optimization in next generation adaptive exoskeleton controllers.
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Affiliation(s)
- Benjamin A. Shafer
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, United States
- Institute for Robotics and Intelligent Machines, Georgia Institute of Technology, Atlanta, GA, United States
| | - Sasha A. Philius
- Joint Department of Biomedical Engineering, North Carolina State University and University of North Carolina at Chapel Hill, Raleigh, NC, United States
| | - Richard W. Nuckols
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, MA, United States
| | - James McCall
- Joint Department of Biomedical Engineering, North Carolina State University and University of North Carolina at Chapel Hill, Raleigh, NC, United States
| | - Aaron J. Young
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, United States
- Institute for Robotics and Intelligent Machines, Georgia Institute of Technology, Atlanta, GA, United States
| | - Gregory S. Sawicki
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, United States
- Institute for Robotics and Intelligent Machines, Georgia Institute of Technology, Atlanta, GA, United States
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13
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Domínguez-Zamora FJ, Marigold DS. Motives driving gaze and walking decisions. Curr Biol 2021; 31:1632-1642.e4. [PMID: 33600769 DOI: 10.1016/j.cub.2021.01.069] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Revised: 10/01/2020] [Accepted: 01/20/2021] [Indexed: 01/23/2023]
Abstract
To navigate complex environments, people must decide how to direct gaze to acquire relevant information and decide where, when, and how to move the body. Recent work supports the idea that gaze may be directed to reduce task-relevant environmental uncertainty and to ensure movement accuracy based on the cost (or effort) to move the body and maintain balance. During walking, these two factors may compete for gaze allocation and explain how we make decisions about where to step. Using a forced-choice walking paradigm, where we manipulated the visual uncertainty (simulating uncertain terrain characteristics) and motor cost associated with specific step-target choices, we examined the motives driving gaze and step decisions. We characterized each individual's distinct gaze behavior based on their sensitivity to changes in visual uncertainty, which predicted step-choice behavior when foot-placement accuracy was important to the task. We show that individuals who tended to look at both target choices as visual uncertainty increased prioritized stepping onto the more certain location after looking at it longer, even at the expense of increased motor cost. In contrast, individuals who tended to look at only one of the target choices as visual uncertainty increased preferred to step on the target that minimized motor cost. Overall, we demonstrate that how a person explores the environment with their eyes dictates where they step. These gaze and step decisions may relate to the value a person assigns to information gain, being certain of their actions, and conserving energy.
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Affiliation(s)
- F Javier Domínguez-Zamora
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Daniel S Marigold
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada.
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Sánchez N, Simha SN, Donelan JM, Finley JM. Using asymmetry to your advantage: learning to acquire and accept external assistance during prolonged split-belt walking. J Neurophysiol 2021; 125:344-357. [PMID: 33296612 PMCID: PMC7948143 DOI: 10.1152/jn.00416.2020] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 11/12/2020] [Accepted: 12/01/2020] [Indexed: 11/22/2022] Open
Abstract
People can learn to exploit external assistance during walking to reduce energetic cost. For example, walking on a split-belt treadmill affords the opportunity for people to redistribute the mechanical work performed by the legs to gain assistance from the difference in belts' speed and reduce energetic cost. Though we know what people should do to acquire this assistance, this strategy is not observed during typical adaptation studies. We hypothesized that extending the time allotted for adaptation would result in participants adopting asymmetric step lengths to increase the assistance they can acquire from the treadmill. Here, participants walked on a split-belt treadmill for 45 min while we measured spatiotemporal gait variables, metabolic cost, and mechanical work. We show that when people are given sufficient time to adapt, they naturally learn to step further forward on the fast belt, acquire positive mechanical work from the treadmill, and reduce the positive work performed by the legs. We also show that spatiotemporal adaptation and energy optimization operate over different timescales: people continue to reduce energetic cost even after spatiotemporal changes have plateaued. Our findings support the idea that walking with symmetric step lengths, which is traditionally thought of as the endpoint of adaptation, is only a point in the process by which people learn to take advantage of the assistance provided by the treadmill. These results provide further evidence that reducing energetic cost is central in shaping adaptive locomotion, but this process occurs over more extended timescales than those used in typical studies.NEW & NOTEWORTHY Split-belt treadmill adaptation can be seen as a process where people learn to acquire positive work from the treadmill to reduce energetic cost. Though we know what people should do to reduce energetic cost, this strategy is not observed during adaptation studies. We extended the duration of adaptation and show that people continuously adapt their gait to acquire positive work from the treadmill to reduce energetic cost. This process requires longer exposure than traditionally allotted.
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Affiliation(s)
- Natalia Sánchez
- Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, California
| | - Surabhi N Simha
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - J Maxwell Donelan
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - James M Finley
- Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, California
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California
- Neuroscience Graduate Program, University of Southern California, Los Angeles, California
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Rosenberg MC, Banjanin BS, Burden SA, Steele KM. Predicting walking response to ankle exoskeletons using data-driven models. J R Soc Interface 2020; 17:20200487. [PMID: 33050782 DOI: 10.1098/rsif.2020.0487] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Despite recent innovations in exoskeleton design and control, predicting subject-specific impacts of exoskeletons on gait remains challenging. We evaluated the ability of three classes of subject-specific phase-varying (PV) models to predict kinematic and myoelectric responses to ankle exoskeletons during walking, without requiring prior knowledge of specific user characteristics. Each model-PV, linear PV (LPV) and nonlinear PV (NPV)-leveraged Floquet theory to predict deviations from a nominal gait cycle due to exoskeleton torque, though the models differed in complexity and expected prediction accuracy. For 12 unimpaired adults walking with bilateral passive ankle exoskeletons, we predicted kinematics and muscle activity in response to three exoskeleton torque conditions. The LPV model's predictions were more accurate than the PV model when predicting less than 12.5% of a stride in the future and explained 49-70% of the variance in hip, knee and ankle kinematic responses to torque. The LPV model also predicted kinematic responses with similar accuracy to the more-complex NPV model. Myoelectric responses were challenging to predict with all models, explaining at most 10% of the variance in responses. This work highlights the potential of data-driven PV models to predict complex subject-specific responses to ankle exoskeletons and inform device design and control.
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Affiliation(s)
- Michael C Rosenberg
- Department of Mechanical Engineering, University of Washington, Seattle, WA, USA
| | - Bora S Banjanin
- Department of Electrical and Computer Engineering, University of Washington, Seattle, WA, USA
| | - Samuel A Burden
- Department of Electrical and Computer Engineering, University of Washington, Seattle, WA, USA
| | - Katherine M Steele
- Department of Mechanical Engineering, University of Washington, Seattle, WA, USA
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Balbinot G, Schuch CP, Bianchi Oliveira H, Peyré-Tartaruga LA. Mechanical and energetic determinants of impaired gait following stroke: segmental work and pendular energy transduction during treadmill walking. Biol Open 2020; 9:9/7/bio051581. [PMID: 32694152 PMCID: PMC7390624 DOI: 10.1242/bio.051581] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Systems biology postulates the balance between energy production and conservation in optimizing locomotion. Here, we analyzed how mechanical energy production and conservation influenced metabolic energy expenditure in stroke survivors during treadmill walking at different speeds. We used the body center of mass (BCoM) and segmental center of mass to calculate mechanical energy production: external and each segment's mechanical work (Wseg). We also estimated energy conservation by applying the pendular transduction framework (i.e. energy transduction within the step; Rint). Energy conservation was likely optimized by the paretic lower-limb acting as a rigid shaft while the non-paretic limb pushed the BCoM forward at the slower walking speed. Wseg production was characterized by greater movements between the limbs and body, a compensatory strategy used mainly by the non-paretic limbs. Overall, Wseg production following a stroke was characterized by non-paretic upper-limb compensation, but also by an exaggerated lift of the paretic leg. This study also highlights how post-stroke subjects may perform a more economic gait while walking on a treadmill at preferred walking speeds. Complex neural adaptations optimize energy production and conservation at the systems level, and may fundament new insights onto post-stroke neurorehabilitation. This article has and associated First Person interview with the first author of the paper. Summary: Walking after a stroke may be energetically consuming. Here, we show how compensations and asymmetries may contribute to increasing the amount of work needed to walk following a stroke.
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Affiliation(s)
- Gustavo Balbinot
- Exercise Research Laboratory, Universidade Federal do Rio Grande do Sul, 750 Felizardo Street, Porto Alegre, 90690-200, RS, Brazil.,KITE - Toronto Rehabilitation Institute - University Health Network, Lyndhurst Centre, 520 Sutherland Drive, Toronto, M4G 3V9, ON, Canada
| | - Clarissa Pedrini Schuch
- Exercise Research Laboratory, Universidade Federal do Rio Grande do Sul, 750 Felizardo Street, Porto Alegre, 90690-200, RS, Brazil
| | - Henrique Bianchi Oliveira
- Exercise Research Laboratory, Universidade Federal do Rio Grande do Sul, 750 Felizardo Street, Porto Alegre, 90690-200, RS, Brazil
| | - Leonardo A Peyré-Tartaruga
- Exercise Research Laboratory, Universidade Federal do Rio Grande do Sul, 750 Felizardo Street, Porto Alegre, 90690-200, RS, Brazil
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