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Mari S, Lecomte CG, Merlet AN, Audet J, Yassine S, Eddaoui O, Genois G, Nadeau C, Harnie J, Rybak IA, Prilutsky BI, Frigon A. Changes in intra- and interlimb reflexes from hindlimb cutaneous afferents after staggered thoracic lateral hemisections during locomotion in cats. J Physiol 2024; 602:1987-2017. [PMID: 38593215 PMCID: PMC11068482 DOI: 10.1113/jp286151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Accepted: 03/04/2024] [Indexed: 04/11/2024] Open
Abstract
When the foot dorsum contacts an obstacle during locomotion, cutaneous afferents signal central circuits to coordinate muscle activity in the four limbs. Spinal cord injury disrupts these interactions, impairing balance and interlimb coordination. We evoked cutaneous reflexes by electrically stimulating left and right superficial peroneal nerves before and after two thoracic lateral hemisections placed on opposite sides of the cord at 9- to 13-week interval in seven adult cats (4 males and 3 females). We recorded reflex responses in ten hindlimb and five forelimb muscles bilaterally. After the first (right T5-T6) and second (left T10-T11) hemisections, coordination of the fore- and hindlimbs was altered and/or became less consistent. After the second hemisection, cats required balance assistance to perform quadrupedal locomotion. Short-latency reflex responses in homonymous and crossed hindlimb muscles largely remained unaffected after staggered hemisections. However, mid- and long-latency homonymous and crossed responses in both hindlimbs occurred less frequently after staggered hemisections. In forelimb muscles, homolateral and diagonal mid- and long-latency response occurrence significantly decreased after the first and second hemisections. In all four limbs, however, when present, short-, mid- and long-latency responses maintained their phase-dependent modulation. We also observed reduced durations of short-latency inhibitory homonymous responses in left hindlimb extensors early after the first hemisection and delayed short-latency responses in the right ipsilesional hindlimb after the first hemisection. Therefore, changes in cutaneous reflex responses correlated with impaired balance/stability and interlimb coordination during locomotion after spinal cord injury. Restoring reflex transmission could be used as a biomarker to facilitate locomotor recovery. KEY POINTS: Cutaneous afferent inputs coordinate muscle activity in the four limbs during locomotion when the foot dorsum contacts an obstacle. Thoracic spinal cord injury disrupts communication between spinal locomotor centres located at cervical and lumbar levels, impairing balance and limb coordination. We investigated cutaneous reflexes during quadrupedal locomotion by electrically stimulating the superficial peroneal nerve bilaterally, before and after staggered lateral thoracic hemisections of the spinal cord in cats. We showed a loss/reduction of mid- and long-latency responses in all four limbs after staggered hemisections, which correlated with altered coordination of the fore- and hindlimbs and impaired balance. Targeting cutaneous reflex pathways projecting to the four limbs could help develop therapeutic approaches aimed at restoring transmission in ascending and descending spinal pathways.
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Affiliation(s)
- Stephen Mari
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada
| | - Charly G. Lecomte
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada
| | - Angèle N. Merlet
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada
| | - Johannie Audet
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada
| | - Sirine Yassine
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada
| | - Oussama Eddaoui
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada
| | - Gabriel Genois
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada
| | - Charlène Nadeau
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada
| | - Jonathan Harnie
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada
| | - Ilya A. Rybak
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Boris I. Prilutsky
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, United States
| | - Alain Frigon
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada
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Mari S, Lecomte CG, Merlet AN, Audet J, Yassine S, Eddaoui O, Genois G, Nadeau C, Harnie J, Rybak IA, Prilutsky BI, Frigon A. Changes in intra- and interlimb reflexes from hindlimb cutaneous afferents after staggered thoracic lateral hemisections during locomotion in cats. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.15.571869. [PMID: 38168183 PMCID: PMC10760189 DOI: 10.1101/2023.12.15.571869] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
When the foot dorsum contacts an obstacle during locomotion, cutaneous afferents signal central circuits to coordinate muscle activity in the four limbs. Spinal cord injury disrupts these interactions, impairing balance and interlimb coordination. We evoked cutaneous reflexes by electrically stimulating left and right superficial peroneal nerves before and after two thoracic lateral hemisections placed on opposite sides of the cord at 9-13 weeks interval in seven adult cats (4 males and 3 females). We recorded reflex responses in ten hindlimb and five forelimb muscles bilaterally. After the first (right T5-T6) and second (left T10-T11) hemisections, coordination of the fore- and hindlimbs was altered and/or became less consistent. After the second hemisection, cats required balance assistance to perform quadrupedal locomotion. Short-latency reflex responses in homonymous and crossed hindlimb muscles largely remained unaffected after staggered hemisections. However, mid- and long-latency homonymous and crossed responses in both hindlimbs occurred less frequently after staggered hemisections. In forelimb muscles, homolateral and diagonal mid- and long-latency response occurrence significantly decreased after the first and second hemisections. In all four limbs, however, when present, short-, mid- and long-latency responses maintained their phase-dependent modulation. We also observed reduced durations of short-latency inhibitory homonymous responses in left hindlimb extensors early after the first hemisection and delayed short-latency responses in the right ipsilesional hindlimb after the first hemisection. Therefore, changes in cutaneous reflex responses correlated with impaired balance/stability and interlimb coordination during locomotion after spinal cord injury. Restoring reflex transmission could be used as a biomarker to facilitate locomotor recovery.
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Affiliation(s)
- Stephen Mari
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada
| | - Charly G. Lecomte
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada
| | - Angèle N. Merlet
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada
| | - Johannie Audet
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada
| | - Sirine Yassine
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada
| | - Oussama Eddaoui
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada
| | - Gabriel Genois
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada
| | - Charlène Nadeau
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada
| | - Jonathan Harnie
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada
| | - Ilya A. Rybak
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Boris I. Prilutsky
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, United States
| | - Alain Frigon
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, Canada
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Mari S, Lecomte CG, Merlet AN, Audet J, Harnie J, Rybak IA, Prilutsky BI, Frigon A. A sensory signal related to left-right symmetry modulates intra- and interlimb cutaneous reflexes during locomotion in intact cats. Front Syst Neurosci 2023; 17:1199079. [PMID: 37360774 PMCID: PMC10288215 DOI: 10.3389/fnsys.2023.1199079] [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: 04/02/2023] [Accepted: 05/22/2023] [Indexed: 06/28/2023] Open
Abstract
Introduction During locomotion, cutaneous reflexes play an essential role in rapidly responding to an external perturbation, for example, to prevent a fall when the foot contacts an obstacle. In cats and humans, cutaneous reflexes involve all four limbs and are task- and phase modulated to generate functionally appropriate whole-body responses. Methods To assess task-dependent modulation of cutaneous interlimb reflexes, we electrically stimulated the superficial radial or superficial peroneal nerves in adult cats and recorded muscle activity in the four limbs during tied-belt (equal left-right speeds) and split-belt (different left-right speeds) locomotion. Results We show that the pattern of intra- and interlimb cutaneous reflexes in fore- and hindlimbs muscles and their phase-dependent modulation were conserved during tied-belt and split-belt locomotion. Short-latency cutaneous reflex responses to muscles of the stimulated limb were more likely to be evoked and phase-modulated when compared to muscles in the other limbs. In some muscles, the degree of reflex modulation was significantly reduced during split-belt locomotion compared to tied-belt conditions. Split-belt locomotion increased the step-by-step variability of left-right symmetry, particularly spatially. Discussion These results suggest that sensory signals related to left-right symmetry reduce cutaneous reflex modulation, potentially to avoid destabilizing an unstable pattern.
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Affiliation(s)
- Stephen Mari
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Charly G. Lecomte
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Angèle N. Merlet
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Johannie Audet
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Jonathan Harnie
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Ilya A. Rybak
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Boris I. Prilutsky
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, United States
| | - Alain Frigon
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
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Abstract
When animals walk overground, mechanical stimuli activate various receptors located in muscles, joints, and skin. Afferents from these mechanoreceptors project to neuronal networks controlling locomotion in the spinal cord and brain. The dynamic interactions between the control systems at different levels of the neuraxis ensure that locomotion adjusts to its environment and meets task demands. In this article, we describe and discuss the essential contribution of somatosensory feedback to locomotion. We start with a discussion of how biomechanical properties of the body affect somatosensory feedback. We follow with the different types of mechanoreceptors and somatosensory afferents and their activity during locomotion. We then describe central projections to locomotor networks and the modulation of somatosensory feedback during locomotion and its mechanisms. We then discuss experimental approaches and animal models used to investigate the control of locomotion by somatosensory feedback before providing an overview of the different functional roles of somatosensory feedback for locomotion. Lastly, we briefly describe the role of somatosensory feedback in the recovery of locomotion after neurological injury. We highlight the fact that somatosensory feedback is an essential component of a highly integrated system for locomotor control. © 2021 American Physiological Society. Compr Physiol 11:1-71, 2021.
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Affiliation(s)
- Alain Frigon
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Quebec, Canada
| | - Turgay Akay
- Department of Medical Neuroscience, Atlantic Mobility Action Project, Brain Repair Center, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Boris I Prilutsky
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
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Fang J, Hunt KJ. Mechanical Design and Control System Development of a Rehabilitation Robotic System for Walking With Arm Swing. FRONTIERS IN REHABILITATION SCIENCES 2021; 2:720182. [PMID: 36188797 PMCID: PMC9397737 DOI: 10.3389/fresc.2021.720182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Accepted: 10/21/2021] [Indexed: 11/13/2022]
Abstract
Background: Interlimb neural coupling implies that arm swing should be included during gait training to improve rehabilitation outcomes. We previously developed several systems for production of walking with arm swing, but the reaction forces on the foot sole during usage of the systems were not satisfactory and there was potential to improve control system performance. This work aimed to design and technically evaluate a novel system for producing walking with synchronised arm and leg movement and with dynamic force loading on the foot soles. Methods: The robotic system included a passive curved treadmill and a trunk frame, upon which the rigs for the upper and lower limbs were mounted. Ten actuators and servocontrollers with EtherCAT communication protocol controlled the bilateral shoulder, elbow, hip, knee and ankle joints. Impedance control algorithms were developed and ran in an industrial PC. Flexible pressure sensors recorded the plantar forces on the foot soles. The criteria of implementation and responsiveness were used to formally evaluate the technical feasibility of the system. Results: Using impedance algorithms, the system produced synchronous walking with arm swing on the curved treadmill, with mean RMS angular tracking error <2° in the 10 joint profiles. The foot trajectories relative to the hip presented similar shapes to those during normal gait, with mean RMS displacement error <1.5 cm. A force pattern that started at the heel and finished at the forefoot was observed during walking using the system, which was similar to the pattern from overground walking. Conclusion: The robotic system produced walking-like kinematics in the 10 joints and in the foot trajectories. Integrated with the curved treadmill, the system also produced walking-like force patterns on the foot soles. The system is considered feasible as far as implementation and responsiveness are concerned. Future work will focus on improvement of the mechanical system for future clinical application.
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Misiaszek JE, Hackett H, McMahon AJ, Krutz J. Influence of a light touch reference on cutaneous reflexes from the hand during standing. Exp Brain Res 2021; 239:787-796. [PMID: 33398453 DOI: 10.1007/s00221-020-06019-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 12/11/2020] [Indexed: 11/25/2022]
Abstract
Light touch of a stable reference reduces sway during standing. However, unexpected displacement of a light touch reference leads to short-latency reactions in ankle muscles consistent with a balance reaction, that are replaced by responses in arm muscles on subsequent trials. We anticipated that the excitability of sensorimotor pathways arising from finger cutaneous afferents would reflect these changes in behavior. We hypothesized that (1) interlimb cutaneous reflexes in muscles of the ipsilateral leg, derived from median nerve (MED) stimulation would be facilitated when touch was stable, but reduced when touch was unreliable, (2) intralimb MED reflexes in muscles of the homonymous arm would be facilitated when touch was unreliable and participants tracked the touch reference with arm movements, and (3) radial nerve (RAD) evoked reflexes would be unaffected, given that the RAD innervation territory is not involved in the light touch task. Cutaneous reflexes were evoked using a transcutaneous train of pulses (5 × 1.0 ms square-wave pulses; 300 Hz) and recorded using electromyography of muscles of the ipsilateral arm and leg. As hypothesized, interlimb MED reflexes recorded in soleus (SOL) were larger when touching the stable reference (mean ± SD % MVC; 4.78 ± 1.57) than when not touching a reference (1.00 ± 1.05) or when touching an unstable reference (1.07 ± 1.16). In addition, intralimb MED reflexes in anterior deltoid (AD) were larger when touching an unstable reference (4.50 ± 1.31), compared to touching a stable reference (1.34 ± 1.01) or not touching (1.50 ± 1.00). In contrast, interlimb RAD reflexes in SOL were larger when not touching (4.29 ± 4.34), compared with touching a stable (1.14 ± 1.84) or unstable reference (3.11 ± 4.15). These findings indicate that cutaneous reflexes from the hand are scaled with a rapid change in motor behavior when a touch reference becomes unstable, suggesting that spinal sensorimotor pathways are functionally reweighted based in part upon the reliability of tactile inputs.
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Affiliation(s)
- John E Misiaszek
- Department of Occupational Therapy, Faculty of Rehabilitation Medicine, University of Alberta, 2-64 Corbett Hall, Edmonton, AB, T6G 2G4, Canada.
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada.
| | - Heather Hackett
- Department of Occupational Therapy, Faculty of Rehabilitation Medicine, University of Alberta, 2-64 Corbett Hall, Edmonton, AB, T6G 2G4, Canada
| | - Arden J McMahon
- Department of Occupational Therapy, Faculty of Rehabilitation Medicine, University of Alberta, 2-64 Corbett Hall, Edmonton, AB, T6G 2G4, Canada
| | - Jason Krutz
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
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Klarner T, Pearcey GEP, Sun Y, Barss TS, Zehr EP. Changing coupling between the arms and legs with slow walking speeds alters regulation of somatosensory feedback. Exp Brain Res 2020; 238:1335-1349. [PMID: 32333034 DOI: 10.1007/s00221-020-05813-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2020] [Accepted: 04/13/2020] [Indexed: 11/30/2022]
Abstract
Arm swing movement is coordinated with movement of the legs during walking, where the frequency of coordination depends on walking speed. At typical speeds, arm and leg movements, respectively, are frequency locked in a 1:1 ratio but at slow speeds this changes to a 2:1 ratio. It is unknown if the changes in interlimb ratio that accompany slow walking speeds alters regulation of somatosensory feedback. To probe the neural interactions between the arms and legs, somatosensory linkages in the form of interlimb cutaneous reflexes were examined. It was hypothesized that different interlimb frequencies and walking speeds would result in changes in the modulation of cutaneous reflexes between the arms and legs. To test this hypothesis, participants walked in four combinations of walking speed (typical, slow) and interlimb coordination (1:1, and 2:1), while cutaneous reflexes and background muscle activity were evaluated with stimulation applied to the superficial peroneal nerve at the ankle and superficial radial nerve at the wrist. Results show main effects of interlimb coordination and walking speed on cutaneous reflex modulation, effects are largest in the swing phase, and a directional coupling was observed, where changes in the frequency of arm movements had a greater effect on muscle activity in the legs compared to the reverse. Task-dependent modulation was also revealed from stimulation at local and remote sources. Understanding the underlying neural mechanisms for the organization of rhythmic arm movement, and its coordination with the legs in healthy participants, can give insight into pathological walking, and will facilitate the development of effective strategies for the rehabilitation of walking.
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Affiliation(s)
- Taryn Klarner
- School of Kinesiology, Lakehead University, Thunder Bay, Canada.,Rehabilitation Neuroscience Laboratory, University of Victoria, PO Box 3010 STN CSC, Victoria, BC, V8W 3P1, Canada.,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada
| | - Gregory E P Pearcey
- Rehabilitation Neuroscience Laboratory, University of Victoria, PO Box 3010 STN CSC, Victoria, BC, V8W 3P1, Canada.,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada.,Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada
| | - Yao Sun
- Rehabilitation Neuroscience Laboratory, University of Victoria, PO Box 3010 STN CSC, Victoria, BC, V8W 3P1, Canada.,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada.,Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada
| | - Trevor S Barss
- Rehabilitation Neuroscience Laboratory, University of Victoria, PO Box 3010 STN CSC, Victoria, BC, V8W 3P1, Canada.,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada.,Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada
| | - E Paul Zehr
- Rehabilitation Neuroscience Laboratory, University of Victoria, PO Box 3010 STN CSC, Victoria, BC, V8W 3P1, Canada. .,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada. .,Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada. .,Division of Medical Sciences, University of Victoria, Victoria, BC, Canada.
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Pearcey GEP, Zehr EP. We Are Upright-Walking Cats: Human Limbs as Sensory Antennae During Locomotion. Physiology (Bethesda) 2020; 34:354-364. [PMID: 31389772 DOI: 10.1152/physiol.00008.2019] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Humans and cats share many characteristics pertaining to the neural control of locomotion, which has enabled the comprehensive study of cutaneous feedback during locomotion. Feedback from discrete skin regions on both surfaces of the human foot has revealed that neuromechanical responses are highly topographically organized and contribute to "sensory guidance" of our limbs during locomotion.
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Affiliation(s)
- Gregory E P Pearcey
- Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, British Columbia, Canada.,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, British Columbia, Canada.,Centre for Biomedical Research, University of Victoria, Victoria, British Columbia, Canada
| | - E Paul Zehr
- Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, British Columbia, Canada.,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, British Columbia, Canada.,Centre for Biomedical Research, University of Victoria, Victoria, British Columbia, Canada.,Division of Medical Sciences, University of Victoria, British Columbia, Canada.,Zanshin Consulting, Inc., Victoria, British Columbia, Canada
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9
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Intralimb and Interlimb Cutaneous Reflexes during Locomotion in the Intact Cat. J Neurosci 2018; 38:4104-4122. [PMID: 29563181 DOI: 10.1523/jneurosci.3288-17.2018] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 03/03/2018] [Accepted: 03/09/2018] [Indexed: 12/30/2022] Open
Abstract
When the foot contacts an obstacle during locomotion, cutaneous inputs activate spinal circuits to ensure dynamic balance and forward progression. In quadrupeds, this requires coordinated reflex responses between the four limbs. Here, we investigated the patterns and phasic modulation of cutaneous reflexes in forelimb and hindlimb muscles evoked by inputs from all four limbs. Five female cats were implanted to record muscle activity and to stimulate the superficial peroneal and superficial radial nerves during locomotion. Stimulating these nerves evoked short-, mid-, and longer-latency excitatory and/or inhibitory responses in all four limbs that were phase-dependent. The largest responses were generally observed during the peak activity of the muscle. Cutaneous reflexes during mid-swing were consistent with flexion of the homonymous limb and accompanied by modification of the stance phases of the other three limbs, by coactivating flexors and extensors and/or by delaying push-off. Cutaneous reflexes during mid-stance were consistent with stabilizing the homonymous limb by delaying and then facilitating its push-off and modifying the support phases of the homolateral and diagonal limbs, characterized by coactivating flexors and extensors, reinforcing extensor activity and/or delaying push-off. The shortest latencies of homolateral and diagonal responses were consistent with fast-conducting disynaptic or trisynaptic pathways. Descending homolateral and diagonal pathways from the forelimbs to the hindlimbs had a higher probability of eliciting responses compared with ascending pathways from the hindlimbs to the forelimbs. Thus, in quadrupeds, intralimb and interlimb reflexes activated by cutaneous inputs ensure dynamic coordination of the four limbs, producing a whole-body response.SIGNIFICANCE STATEMENT The skin contains receptors that, when activated, send inputs to spinal circuits, signaling a perturbation. Rapid responses, or reflexes, in muscles of the contacted limb and opposite homologous limb help maintain balance and forward progression. Here, we investigated reflexes during quadrupedal locomotion in the cat by electrically stimulating cutaneous nerves in each of the four limbs. Functionally, responses appear to modify the trajectory or stabilize the movement of the stimulated limb while modifying the support phase of the other limbs. Reflexes between limbs are mediated by fast-conducting pathways that involve excitatory and inhibitory circuits controlling each limb. The comparatively stronger descending pathways from cervical to lumbar circuits controlling the forelimbs and hindlimbs, respectively, could serve a protective function.
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Kaupp C, Pearcey GEP, Klarner T, Sun Y, Cullen H, Barss TS, Zehr EP. Rhythmic arm cycling training improves walking and neurophysiological integrity in chronic stroke: the arms can give legs a helping hand in rehabilitation. J Neurophysiol 2017; 119:1095-1112. [PMID: 29212917 DOI: 10.1152/jn.00570.2017] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Training locomotor central pattern-generating networks (CPGs) through arm and leg cycling improves walking in chronic stroke. These outcomes are presumed to result from enhanced interlimb connectivity and CPG function. The extent to which rhythmic arm training activates interlimb CPG networks for locomotion remains unclear and was assessed by studying chronic stroke participants before and after 5 wk of arm cycling training. Strength was assessed bilaterally via maximal voluntary isometric contractions in the legs and hands. Muscle activation during arm cycling and transfer to treadmill walking were assessed in the more affected (MA) and less affected (LA) sides via surface electromyography. Changes to interlimb coupling during rhythmic movement were evaluated using modulation of cutaneous reflexes elicited by electrical stimulation of the superficial radial nerve at the wrist. Bilateral soleus stretch reflexes were elicited at rest and during 1-Hz arm cycling. Clinical function tests assessed walking, balance, and motor function. Results show significant changes in function and neurophysiological integrity. Training increased bilateral grip strength, force during MA plantarflexion, and muscle activation. "Normalization" of cutaneous reflex modulation was found during arm cycling. There was enhanced activity in the dorsiflexor muscles on the MA side during the swing phase of walking. Enhanced interlimb coupling was shown by increased modulation of MA soleus stretch reflex amplitudes during arm cycling after training. Clinical evaluations showed enhanced walking ability and balance. These results are consistent with training-induced changes in CPG function and interlimb connectivity and underscore the need for arm training in the functional rehabilitation of walking after neurotrauma. NEW & NOTEWORTHY It has been suggested but not tested that training the arms may influence rehabilitation of walking due to activation of interneuronal patterning networks after stroke. We show that arm cycling training improves strength, clinical function, coordination of muscle activity during walking, and neurological connectivity between the arms and the legs. The arms can, in fact, give the legs a helping hand in rehabilitation of walking after stroke.
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Affiliation(s)
- Chelsea Kaupp
- Rehabilitation Neuroscience Laboratory, University of Victoria , Victoria, British Columbia , Canada.,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD) , Vancouver, British Columbia , Canada.,Centre for Biomedical Research, University of Victoria , Victoria, British Columbia , Canada
| | - Gregory E P Pearcey
- Rehabilitation Neuroscience Laboratory, University of Victoria , Victoria, British Columbia , Canada.,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD) , Vancouver, British Columbia , Canada.,Centre for Biomedical Research, University of Victoria , Victoria, British Columbia , Canada
| | - Taryn Klarner
- Rehabilitation Neuroscience Laboratory, University of Victoria , Victoria, British Columbia , Canada.,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD) , Vancouver, British Columbia , Canada.,Centre for Biomedical Research, University of Victoria , Victoria, British Columbia , Canada
| | - Yao Sun
- Rehabilitation Neuroscience Laboratory, University of Victoria , Victoria, British Columbia , Canada.,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD) , Vancouver, British Columbia , Canada.,Centre for Biomedical Research, University of Victoria , Victoria, British Columbia , Canada
| | - Hilary Cullen
- Rehabilitation Neuroscience Laboratory, University of Victoria , Victoria, British Columbia , Canada.,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD) , Vancouver, British Columbia , Canada.,Centre for Biomedical Research, University of Victoria , Victoria, British Columbia , Canada
| | - Trevor S Barss
- Human Neurophysiology Laboratory, University of Alberta , Edmonton, Alberta , Canada
| | - E Paul Zehr
- Rehabilitation Neuroscience Laboratory, University of Victoria , Victoria, British Columbia , Canada.,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD) , Vancouver, British Columbia , Canada.,Centre for Biomedical Research, University of Victoria , Victoria, British Columbia , Canada.,Division of Medical Sciences, University of Victoria , Victoria, British Columbia , Canada
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11
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KLARNER TARYN, PEARCEY GREGORYEP, SUN YAO, BARSS TREVORS, KAUPP CHELSEA, MUNRO BRIDGET, FRANK NICK, ZEHR EPAUL. Beyond the Bottom of the Foot. Med Sci Sports Exerc 2017; 49:2439-2450. [DOI: 10.1249/mss.0000000000001389] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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12
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The effects of haptic input on biomechanical and neurophysiological parameters of walking: A scoping review. Gait Posture 2017; 58:232-239. [PMID: 28822328 DOI: 10.1016/j.gaitpost.2017.08.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 06/19/2017] [Accepted: 08/06/2017] [Indexed: 02/02/2023]
Abstract
Walking is an important component of daily life requiring sensorimotor integration to be successful. Adding haptic input via light touch or anchors has been shown to improve standing balance; however, the effect of adding haptic input on walking is not clear. This scoping review systematically summarizes the current evidence regarding the addition of haptic input on walking in adults. Following an established protocol, relevant studies were identified using indexed data bases (Medline, EMBASE, PsychINFO, Google Scholar) and hand searches of published review articles on related topics. 644 references were identified and screened by a minimum of two independent researchers before data was extracted from 17 studies. A modified TREND tool was used to assess quality of the references which showed that the majority of studies were of moderate or high quality. Results show that adding haptic input changes walking behaviour. In particular, there is an immediate reduction in variability of gait step parameters and whole body stability, as well as a decrease in lower limb muscle activity. The effect of added haptic input on reflex modulation may depend on the limb of interest (i.e., upper or lower limb). Many studies did not clearly describe the amount and/or direction of haptic input applied. This information is needed to replicate and/or advance their results. More investigations into the use and design of the haptic tools, the attentional demands of adding haptic input, and clarity on short-term effects are needed. In addition, more is research needed to determine whether adding haptic input has significant, lasting benefits that may translate to fall prevention efforts.
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13
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Klarner T, Barss TS, Sun Y, Kaupp C, Loadman PM, Zehr EP. Long-Term Plasticity in Reflex Excitability Induced by Five Weeks of Arm and Leg Cycling Training after Stroke. Brain Sci 2016; 6:brainsci6040054. [PMID: 27827888 PMCID: PMC5187568 DOI: 10.3390/brainsci6040054] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Revised: 10/22/2016] [Accepted: 10/28/2016] [Indexed: 12/21/2022] Open
Abstract
Neural connections remain partially viable after stroke, and access to these residual connections provides a substrate for training-induced plasticity. The objective of this project was to test if reflex excitability could be modified with arm and leg (A & L) cycling training. Nineteen individuals with chronic stroke (more than six months postlesion) performed 30 min of A & L cycling training three times a week for five weeks. Changes in reflex excitability were inferred from modulation of cutaneous and stretch reflexes. A multiple baseline (three pretests) within-subject control design was used. Plasticity in reflex excitability was determined as an increase in the conditioning effect of arm cycling on soleus stretch reflex amplitude on the more affected side, by the index of modulation, and by the modulation ratio between sides for cutaneous reflexes. In general, A & L cycling training induces plasticity and modifies reflex excitability after stroke.
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Affiliation(s)
- Taryn Klarner
- Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, BC V8W 3P1, Canada.
- Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC V5Z 1M9, Canada.
- Centre for Biomedical Research, University of Victoria, Victoria, BC V8W 2Y2, Canada.
| | - Trevor S Barss
- Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, BC V8W 3P1, Canada.
- Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC V5Z 1M9, Canada.
- Centre for Biomedical Research, University of Victoria, Victoria, BC V8W 2Y2, Canada.
| | - Yao Sun
- Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, BC V8W 3P1, Canada.
- Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC V5Z 1M9, Canada.
- Centre for Biomedical Research, University of Victoria, Victoria, BC V8W 2Y2, Canada.
| | - Chelsea Kaupp
- Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, BC V8W 3P1, Canada.
- Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC V5Z 1M9, Canada.
- Centre for Biomedical Research, University of Victoria, Victoria, BC V8W 2Y2, Canada.
| | - Pamela M Loadman
- Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, BC V8W 3P1, Canada.
| | - E Paul Zehr
- Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, BC V8W 3P1, Canada.
- Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC V5Z 1M9, Canada.
- Centre for Biomedical Research, University of Victoria, Victoria, BC V8W 2Y2, Canada.
- Division of Medical Sciences, University of Victoria, BC V8P 5C2, Canada.
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14
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Zehr EP, Barss TS, Dragert K, Frigon A, Vasudevan EV, Haridas C, Hundza S, Kaupp C, Klarner T, Klimstra M, Komiyama T, Loadman PM, Mezzarane RA, Nakajima T, Pearcey GEP, Sun Y. Neuromechanical interactions between the limbs during human locomotion: an evolutionary perspective with translation to rehabilitation. Exp Brain Res 2016; 234:3059-3081. [PMID: 27421291 PMCID: PMC5071371 DOI: 10.1007/s00221-016-4715-4] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 06/27/2016] [Indexed: 11/10/2022]
Abstract
During bipedal locomotor activities, humans use elements of quadrupedal neuronal limb control. Evolutionary constraints can help inform the historical ancestry for preservation of these core control elements support transfer of the huge body of quadrupedal non-human animal literature to human rehabilitation. In particular, this has translational applications for neurological rehabilitation after neurotrauma where interlimb coordination is lost or compromised. The present state of the field supports including arm activity in addition to leg activity as a component of gait retraining after neurotrauma.
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Affiliation(s)
- E P Zehr
- Rehabilitation Neuroscience Laboratory, University of Victoria, PO Box 3010 STN CSC, Victoria, BC, Canada, V8W 3P1.
- Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada.
- Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada.
- Division of Medical Sciences, University of Victoria, Victoria, BC, Canada.
| | - Trevor S Barss
- Rehabilitation Neuroscience Laboratory, University of Victoria, PO Box 3010 STN CSC, Victoria, BC, Canada, V8W 3P1
- Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada
- Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada
| | - Katie Dragert
- Rehabilitation Neuroscience Laboratory, University of Victoria, PO Box 3010 STN CSC, Victoria, BC, Canada, V8W 3P1
| | - Alain Frigon
- Department of Pharmacology-physiology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, QC, Canada
| | - Erin V Vasudevan
- Department of Physical Therapy, SUNY Stony Brook University, Stony Brook, NY, USA
| | - Carlos Haridas
- Rehabilitation Neuroscience Laboratory, University of Victoria, PO Box 3010 STN CSC, Victoria, BC, Canada, V8W 3P1
| | - Sandra Hundza
- Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada
- Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada
- Motion and Mobility Rehabilitation Laboratory, University of Victoria, Victoria, BC, Canada
| | - Chelsea Kaupp
- Rehabilitation Neuroscience Laboratory, University of Victoria, PO Box 3010 STN CSC, Victoria, BC, Canada, V8W 3P1
- Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada
- Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada
| | - Taryn Klarner
- Rehabilitation Neuroscience Laboratory, University of Victoria, PO Box 3010 STN CSC, Victoria, BC, Canada, V8W 3P1
- Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada
- Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada
| | - Marc Klimstra
- Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada
- Motion and Mobility Rehabilitation Laboratory, University of Victoria, Victoria, BC, Canada
| | - Tomoyoshi Komiyama
- Division of Sports and Health Science, Chiba University, Chiba, Japan
- The United Graduate School of Education, Tokyo Gakugei University, Tokyo, Japan
| | - Pamela M Loadman
- Rehabilitation Neuroscience Laboratory, University of Victoria, PO Box 3010 STN CSC, Victoria, BC, Canada, V8W 3P1
- Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada
- Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada
| | - Rinaldo A Mezzarane
- Laboratory of Signal Processing and Motor Control, College of Physical Education, Universidade de Brasília-UnB, Brasília, Brazil
| | - Tsuyoshi Nakajima
- Department of Integrative Physiology, Kyorin University School of Medicine, Tokyo, Japan
| | - Gregory E P Pearcey
- Rehabilitation Neuroscience Laboratory, University of Victoria, PO Box 3010 STN CSC, Victoria, BC, Canada, V8W 3P1
- Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada
- Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada
| | - Yao Sun
- Rehabilitation Neuroscience Laboratory, University of Victoria, PO Box 3010 STN CSC, Victoria, BC, Canada, V8W 3P1
- Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada
- Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada
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15
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Jacobs JV. A review of stairway falls and stair negotiation: Lessons learned and future needs to reduce injury. Gait Posture 2016; 49:159-167. [PMID: 27427833 DOI: 10.1016/j.gaitpost.2016.06.030] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Revised: 05/27/2016] [Accepted: 06/23/2016] [Indexed: 02/02/2023]
Abstract
Stairways are a common location for falls, and they result in a disproportionate risk of death or severe injury. Stairway falls are a significant problem across the lifespan and are often coincident with risky behaviors during stair use. The mechanics of successful stair negotiation for healthy young and older adults have been well described. These studies imply that current stair design does not offer an optimal universal design to meet the needs of older adults or people with health conditions. In addition, impaired stair negotiation associates with more than impaired strength, including functional impairments of cognitive load, sensory function and central motor coordination. Identification of behavioral strategies or stairway environments that assist or hinder recovery from a loss of balance on stairs remains incomplete. Therefore, future studies should investigate the mechanisms of balance recovery on stairs as well as the effectiveness of environmental interventions to mitigate stairway falls and injuries. Potential areas for evaluation may include modifying stair dimensions, surfaces, handrails, visual cues, and removing distractors of attention. Studies should also evaluate combinatorial interventions on person-related factors, such as behavioral interventions to decrease risky behaviors during stair use as well as interventions on cognitive, sensory, and motor functions relevant to stair use. Moreover, future studies should take advantage of new technologies to record stair use outside the laboratory in order to identify people or locations at risk for stairway falls. Such studies would inform the potential for broad-spectrum programs that decrease the risk of stairway falls and injuries.
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Affiliation(s)
- Jesse V Jacobs
- Center for Physical Ergonomics, Liberty Mutual Research Institute for Safety, 71 Frankland Rd., Hopkinton, MA, 01748, USA.
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16
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Exploiting Interlimb Arm and Leg Connections for Walking Rehabilitation: A Training Intervention in Stroke. Neural Plast 2016; 2016:1517968. [PMID: 27403344 PMCID: PMC4926010 DOI: 10.1155/2016/1517968] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 04/20/2016] [Accepted: 05/10/2016] [Indexed: 01/13/2023] Open
Abstract
Rhythmic arm and leg (A&L) movements share common elements of neural control. The extent to which A&L cycling training can lead to training adaptations which transfer to improved walking function remains untested. The purpose of this study was to test the efficacy of A&L cycling training as a modality to improve locomotor function after stroke. Nineteen chronic stroke (>six months) participants were recruited and performed 30 minutes of A&L cycling training three times a week for five weeks. Changes in walking function were assessed with (1) clinical tests; (2) strength during isometric contractions; and (3) treadmill walking performance and cutaneous reflex modulation. A multiple baseline (3 pretests) within-subject control design was used. Data show that A&L cycling training improved clinical walking status increased strength by ~25%, improved modulation of muscle activity by ~25%, increased range of motion by ~20%, decreased stride duration, increased frequency, and improved modulation of cutaneous reflexes during treadmill walking. On most variables, the majority of participants showed a significant improvement in walking ability. These results suggest that exploiting arm and leg connections with A&L cycling training, an accessible and cost-effective training modality, could be used to improve walking ability after stroke.
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17
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Suzuki S, Nakajima T, Futatsubashi G, Mezzarane RA, Ohtsuka H, Ohki Y, Zehr EP, Komiyama T. Soleus Hoffmann reflex amplitudes are specifically modulated by cutaneous inputs from the arms and opposite leg during walking but not standing. Exp Brain Res 2016; 234:2293-304. [PMID: 27030502 DOI: 10.1007/s00221-016-4635-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 03/18/2016] [Indexed: 11/24/2022]
Abstract
Electrical stimulation of cutaneous nerves innervating heteronymous limbs (the arms or contralateral leg) modifies the excitability of soleus Hoffmann (H-) reflexes. The differences in the sensitivities of the H-reflex pathway to cutaneous afferents from different limbs and their modulation during the performance of motor tasks (i.e., standing and walking) are not fully understood. In the present study, we investigated changes in soleus H-reflex amplitudes induced by electrical stimulation of peripheral nerves. Selected targets for conditioning stimulation included the superficial peroneal nerve, which innervates the foot dorsum in the contralateral ankle (cSP), and the superficial radial nerve, which innervates the dorsum of the hand in the ipsilateral (iSR) or contralateral wrist (cSR). Stimulation and subsequent reflex assessment took place during the standing and early-stance phase of treadmill walking in ten healthy subjects. Cutaneous stimulation produced long-latency inhibition (conditioning-test interval of ~100 ms) of the H-reflex during the early-stance phase of walking, and the inhibition was stronger following cSP stimulation compared with iSR or cSR stimulation. In contrast, although similar conditioning stimulation significantly facilitated the H-reflex during standing, this effect remained constant irrespective of the different conditioning sites. These findings suggest that cutaneous inputs from the arms and contralateral leg had reversible effects on the H-reflex amplitudes, including inhibitions with different sensitivities during the early-stance phase of walking and facilitation during standing. Furthermore, the differential sensitivities of the H-reflex modulations were expressed only during walking when the locations of the afferent inputs were functionally relevant.
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Affiliation(s)
- Shinya Suzuki
- Division of Health and Sports Education, The United Graduate School of Education, Tokyo Gakugei University, Tokyo, Japan. .,Department of Integrative Physiology, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, Tokyo, 181-8611, Japan.
| | - Tsuyoshi Nakajima
- Department of Integrative Physiology, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, Tokyo, 181-8611, Japan
| | - Genki Futatsubashi
- Division of Health and Sports Education, The United Graduate School of Education, Tokyo Gakugei University, Tokyo, Japan.,Faculty of Business and Information Sciences, Jobu University, Isesaki, Gunma, Japan
| | - Rinaldo A Mezzarane
- Laboratory of Signal Processing and Motor Control, College of Physical Education, University of Brasília, Brasília, Brazil.,Biomedical Engineering Laboratory, EPUSP, PTC, University of São Paulo, São Paulo, Brazil.,Division of Health and Sports Sciences, Faculty of Education, Chiba University, Chiba, Japan
| | - Hiroyuki Ohtsuka
- Department of Physical Therapy, School of Rehabilitation Sciences, Health Sciences University of Hokkaido, Hokkaido, Japan
| | - Yukari Ohki
- Department of Integrative Physiology, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, Tokyo, 181-8611, Japan
| | - E Paul Zehr
- Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, BC, Canada.,Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada.,International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada
| | - Tomoyoshi Komiyama
- Division of Health and Sports Education, The United Graduate School of Education, Tokyo Gakugei University, Tokyo, Japan.,Division of Health and Sports Sciences, Faculty of Education, Chiba University, Chiba, Japan
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18
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Hoogkamer W, Van Calenbergh F, Swinnen SP, Duysens J. Cutaneous reflex modulation and self-induced reflex attenuation in cerebellar patients. J Neurophysiol 2014; 113:915-24. [PMID: 25392164 DOI: 10.1152/jn.00381.2014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Modulation of cutaneous reflexes is important in the neural control of walking, yet knowledge about underlying neural pathways is still incomplete. Recent studies have suggested that the cerebellum is involved. Here we evaluated the possible roles of the cerebellum in cutaneous reflex modulation and in attenuation of self-induced reflexes. First we checked whether leg muscle activity during walking was similar in patients with focal cerebellar lesions and in healthy control subjects. We then recorded cutaneous reflex activity in leg muscles during walking. Additionally, we compared reflexes after standard (computer triggered) stimuli with reflexes after self-induced stimuli for both groups. Biceps femoris and gastrocnemius medialis muscle activity was increased in the patient group compared with the control subjects, suggesting a coactivation strategy to reduce instability of gait. Cutaneous reflex modulation was similar between healthy control subjects and cerebellar patients, but the latter appeared less able to attenuate reflexes to self-induced stimuli. This suggests that the cerebellum is not primarily involved in cutaneous reflex modulation but that it could act in attenuation of self-induced reflex responses. The latter role in locomotion would be consistent with the common view that the cerebellum predicts sensory consequences of movement.
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Affiliation(s)
- Wouter Hoogkamer
- Movement Control and Neuroplasticity Research Group, Department of Kinesiology, KU Leuven, Leuven, Belgium;
| | - Frank Van Calenbergh
- Department of Neurosurgery, University Hospitals Leuven, KU Leuven, Leuven, Belgium; and
| | - Stephan P Swinnen
- Movement Control and Neuroplasticity Research Group, Department of Kinesiology, KU Leuven, Leuven, Belgium
| | - Jacques Duysens
- Movement Control and Neuroplasticity Research Group, Department of Kinesiology, KU Leuven, Leuven, Belgium; Department of Research, Development, and Education, St. Maartenskliniek, Nijmegen, The Netherlands
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19
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Analysis of descriptive electrophysiological parameters in contralateral interlimb reflexes on tetraplegic patients. Spinal Cord 2014; 52:894-900. [PMID: 25288037 DOI: 10.1038/sc.2014.169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 05/06/2014] [Accepted: 07/07/2014] [Indexed: 11/08/2022]
Abstract
STUDY DESIGN Cross-sectional study. OBJECTIVES The present study aims to analyze and correlate the interlimb reflexes (ILRs), through a standard methodology, in tetraplegic and healthy subjects. The study of the connectivity between the injured spinal cord and the ILR transmission empowers new rehabilitation pathways for tetraplegic patients. SETTING University Hospital-UNICAMP, Campinas, Brazil. METHODS A total of 15 chronic tetraplegic patients and 10 healthy subjects were analyzed with the same methodology. Two tests were performed: (i) In test 1, the stimulus was applied to the right-arm radial nerve and the electromyography (EMG) signal collected in contralateral left tibial muscle. (ii) In test 2, the stimulus was applied to the left-leg fibular nerve and EMG collected in contralateral limb biceps, exploring the opposite direction of the pathway. In both tests, the subjects were stimulated with intensities from 5 to 30 mA (5 mA step) and 40 × 500 μs current modulated pulses. Reflexes were detected from the averaging of the 40 EMG sweeps. RESULTS Each group was analyzed with regard to the reflexes' incidence, amplitude and latency. ILRs were found with similar prominence in both groups. A correlation between the ILR amplitude and the subject injury level was verified. Significant differences were found in the correlation of ILR latency with stimulation charge between healthy and tetraplegic subjects. CONCLUSION The ILR transmission parameters of healthy and tetraplegic subjects were studied. The results obtained strongly suggest a different ILR transmission between healthy and tetraplegic subjects, reinforcing the hypothesis of nerve regeneration after injury.
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20
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Zehr EP, Nakajima T, Barss T, Klarner T, Miklosovic S, Mezzarane RA, Nurse M, Komiyama T. Cutaneous stimulation of discrete regions of the sole during locomotion produces "sensory steering" of the foot. BMC Sports Sci Med Rehabil 2014; 6:33. [PMID: 25202452 PMCID: PMC4158001 DOI: 10.1186/2052-1847-6-33] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Accepted: 07/29/2014] [Indexed: 11/10/2022]
Abstract
BACKGROUND While the neural and mechanical effects of whole nerve cutaneous stimulation on human locomotion have been previously studied, there is less information about effects evoked by activation of discrete skin regions on the sole of the foot. Electrical stimulation of discrete foot regions evokes position-modulated patterns of cutaneous reflexes in muscles acting at the ankle during standing but data during walking are lacking. Here, non-noxious electrical stimulation was delivered to five discrete locations on the sole of the foot (heel, and medial and lateral sites on the midfoot and forefoot) during treadmill walking. EMG activity from muscles acting at the hip, knee and ankle were recorded along with movement at these three joints. Additionally, 3 force sensing resistors measuring continuous force changes were placed at the heel, and the medial and lateral aspects of the right foot sole. All data were sorted based on stimulus occurrence in twelve step-cycle phases, before being averaged together within a phase for subsequent analysis. METHODS Non-noxious electrical stimulation was delivered to five discrete locations on the sole of the foot (heel, and medial and lateral sites on the midfoot and forefoot) during treadmill walking. EMG activity from muscles acting at the hip, knee and ankle were recorded along with movement at these three joints. Additionally, 3 force sensing resistors measuring continuous force changes were placed at the heel, and the medial and lateral aspects of the right foot sole. All data were sorted based on stimulus occurrence in twelve step-cycle phases, before being averaged together within a phase for subsequent analysis. RESULTS The results demonstrate statistically significant dynamic changes in reflex amplitudes, kinematics and foot sole pressures that are site-specific and phase-dependent. The general trends demonstrate responses producing decreased underfoot pressure at the site of stimulation. CONCLUSIONS The responses to stimulation of discrete locations on the foot sole evoke a kind of "sensory steering" that may promote balance and maintenance of locomotion through the modulation of limb loading and foot placement. These results have implications for using sensory stimulation as a therapeutic modality during gait retraining (e.g. after stroke) as well as for footwear design and implementation of foot sole contact surfaces during gait.
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Affiliation(s)
- E Paul Zehr
- Rehabilitation Neuroscience Laboratory, University Victoria, PO Box 3010 STN CSC, Victoria, BC V8W 3P1, Canada ; Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada ; Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada ; Division of Medical Sciences, University of Victoria, Victoria, BC, Canada
| | - Tsuyoshi Nakajima
- Department of Integrative Physiology, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, Japan
| | - Trevor Barss
- Rehabilitation Neuroscience Laboratory, University Victoria, PO Box 3010 STN CSC, Victoria, BC V8W 3P1, Canada ; Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada ; Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada
| | - Taryn Klarner
- Rehabilitation Neuroscience Laboratory, University Victoria, PO Box 3010 STN CSC, Victoria, BC V8W 3P1, Canada ; Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, BC, Canada ; Centre for Biomedical Research, University of Victoria, Victoria, BC, Canada
| | - Stefanie Miklosovic
- Rehabilitation Neuroscience Laboratory, University Victoria, PO Box 3010 STN CSC, Victoria, BC V8W 3P1, Canada
| | - Rinaldo A Mezzarane
- Laboratory of Signal Processing and Motor Control, College of Physical Education, University of Brasília, Brasília, Brazil ; Biomedical Engineering Laboratory, EPUSP, PTC, University of São Paulo, São Paulo, Brazil ; Department of Health and Sports Sciences, Faculty of Education, Chiba University, Chiba, Japan
| | | | - Tomoyoshi Komiyama
- Department of Health and Sports Sciences, Faculty of Education, Chiba University, Chiba, Japan
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21
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The effect of light touch on the amplitude of cutaneous reflexes in the arms during treadmill walking. Exp Brain Res 2014; 232:2967-76. [DOI: 10.1007/s00221-014-3979-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Accepted: 04/26/2014] [Indexed: 10/25/2022]
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22
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Nakajima T, Barss T, Klarner T, Komiyama T, Zehr EP. Amplification of interlimb reflexes evoked by stimulating the hand simultaneously with conditioning from the foot during locomotion. BMC Neurosci 2013; 14:28. [PMID: 23497331 PMCID: PMC3605396 DOI: 10.1186/1471-2202-14-28] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Accepted: 03/07/2013] [Indexed: 11/17/2022] Open
Abstract
Background Widespread interlimb reflexes evoked in leg muscles by cutaneous stimulation of the hand are phase-modulated and behaviorally relevant to produce functional changes in ankle trajectory during walking. These reflexes are complementary to the segmental responses evoked by stimulation at the ankle. Despite differences in the expression of reflex amplitude based upon site of nerve stimulation, there are some common features as well, suggesting the possibility of shared interneuronal pathways. Currently little is known about integration or shared reflex systems from interlimb cutaneous networks during human locomotion. Here we investigated convergent reflex effects following cutaneous stimulation of the hand and foot during arm and leg cycling (AL) by using spatial facilitation. Participants performed AL cycling and static activation of the target muscle knee extensor vastus lateralis (VL) in 3 different randomly ordered nerve stimulation conditions: 1) superficial radial nerve (SR; input from hand); 2) superficial peroneal nerve (SP; input from foot); and, 3) combined stimulation (SR + SP). Stimuli were applied around the onset of rhythmic EMG bursts in VL corresponding to the onset of the power or leg extension phase. Results During AL cycling, small inhibitory (~80 ms) and large facilitatory reflexes (~100 ~ 150 ms) were seen in VL. The amplitudes of the facilitatory responses with SR + SP stimulation were significantly larger than those for SP or SR stimulation alone. The facilitation was also significantly larger than the simple mathematical summation of amplitudes from SP and SR trials. This indicates extra facilitation beyond what would be accounted for by serial neuronal processing and was not observed during static activation. Conclusions We conclude that AL cycling activates shared interneurons in convergent reflex pathways from cutaneous inputs innervating the hand and leg. This enhanced activity has functional implications for corrective responses during locomotion and for translation to rehabilitation after neurotrauma.
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Affiliation(s)
- Tsuyoshi Nakajima
- Department of Integrative Physiology, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, Japan
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Bent LR, Lowrey CR. Single low-threshold afferents innervating the skin of the human foot modulate ongoing muscle activity in the upper limbs. J Neurophysiol 2012; 109:1614-25. [PMID: 23274312 DOI: 10.1152/jn.00608.2012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We have shown for the first time that single cutaneous afferents in the foot dorsum have significant reflex coupling to motoneurons supplying muscles in the upper limb, particularly posterior deltoid and triceps brachii. These observations strengthen what we know from whole nerve stimulation, that skin on the foot and ankle can contribute to the modulation of interlimb muscles in distant innervation territories. The current work provides evidence of the mechanism behind the reflex, where one single skin afferent can evoke a reflex response, rather than a population. Nineteen of forty-one (46%) single cutaneous afferents isolated in the dorsum or plantar surface of the foot elicited a significant modulation of muscle activity in the upper limb. Identification of single afferents in this reflex indicates the strength of the connection and, ultimately, the importance of foot skin in interlimb coordination. The median response magnitude was 2.29% of background EMG, and the size of the evoked response did not significantly differ among the four mechanoreceptor classes (P > 0.1). Interestingly, although the distribution of afferents types did not differ across the foot dorsum, there was a significantly greater coupling response from receptors located on the medial aspect of the foot dorsum (P < 0.01). Furthermore, the most consistent coupling with upper limb muscles was demonstrated by type I afferents (fast and slowly adapting). This work contributes to the current literature on receptor specificity, supporting the view that individual classes of cutaneous afferents may subserve specific roles in kinesthesia, reflexes, and tactile perception.
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Affiliation(s)
- Leah R Bent
- Dept. Human Health and Nutritional Sciences, Univ. of Guelph, Guelph, ON, Canada N1G 2W1.
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Wulf A, Wagner H, Wulf T, Schinowski D, Puta C, Anders C, Chong SY. Phasic bursting pattern of postural responses may reflect internal dynamics: Simulation of trunk reflexes with a neural oscillator model. J Biomech 2012; 45:2645-50. [DOI: 10.1016/j.jbiomech.2012.08.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 08/06/2012] [Accepted: 08/09/2012] [Indexed: 10/27/2022]
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Hoogkamer W, Massaad F, Jansen K, Bruijn SM, Duysens J. Selective bilateral activation of leg muscles after cutaneous nerve stimulation during backward walking. J Neurophysiol 2012; 108:1933-41. [PMID: 22773779 DOI: 10.1152/jn.01159.2011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
During human locomotion, cutaneous reflexes have been suggested to function to preserve balance. Specifically, cutaneous reflexes in the contralateral leg's muscles (with respect to the stimulus) were suggested to play an important role in maintaining stability during locomotor tasks where stability is threatened. We used backward walking (BW) as a paradigm to induce unstable gait and analyzed the cutaneous reflex activity in both ipsilateral and contralateral lower limb muscles after stimulation of the sural nerve at different phases of the gait cycle. In BW, the tibialis anterior (TA) reflex activity in the contralateral leg was markedly higher than TA background EMG activity during its stance phase. In addition, in BW a substantial reflex suppression was observed in the ipsilateral biceps femoris during the stance-swing transition in some participants, while for medial gastrocnemius the reflex activity was equal to background activity in both legs. To test whether the pronounced crossed responses in TA could be related to instability, the responses were correlated with measures of stability (short-term maximum Lyapunov exponents and step width). These measures were higher for BW compared with forward walking, indicating that BW is less stable. However, there was no significant correlation between these measures and the amplitude of the crossed TA responses in BW. It is therefore proposed that these crossed responses are related to an attempt to briefly slow down (TA decelerates the center of mass in the single-stance period) in the light of unexpected perturbations, such as provided by the sural nerve stimulation.
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Affiliation(s)
- Wouter Hoogkamer
- Motor Control Laboratory, Research Center for Movement Control and Neuroplasticity, Department of Kinesiology, KU Leuven, Leuven, Belgium.
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Thompson AK. Interlimb coordination during locomotion: Finding available neural pathways and using them for gait recovery. Clin Neurophysiol 2012; 123:635-7. [DOI: 10.1016/j.clinph.2011.08.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2011] [Revised: 08/19/2011] [Accepted: 08/22/2011] [Indexed: 10/17/2022]
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Zehr EP, Loadman PM. Persistence of locomotor-related interlimb reflex networks during walking after stroke. Clin Neurophysiol 2011; 123:796-807. [PMID: 21945456 DOI: 10.1016/j.clinph.2011.07.049] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Revised: 07/04/2011] [Accepted: 07/07/2011] [Indexed: 11/19/2022]
Abstract
OBJECTIVE Cutaneous nerve stimulation evokes coordinated and phase-modulated reflex output widely distributed to muscles of all four limbs during walking. Accessibility to this distributed network after stroke offers insight into the pathological changes and suggests utility for therapeutic applications. Here we examined muscles in both the more (MA) and less affected (LA) legs evoked by stimulation at the ankle and wrist during walking in chronic (>6 months post CVA) stroke. METHODS Stroke and control participants walked on a treadmill with a harness support system. Reflexes were evoked with trains of electrical stimuli delivered separately to the cutaneous superficial peroneal (SP; at the ankle) and superficial radial (SR; at the wrist) nerves. Background locomotor and reflex EMG were phase-averaged across the gait cycle and analyzed off line. RESULTS Locomotor background muscle activation patterns were altered bilaterally in stroke, as compared with control. Phase-dependent modulation of interlimb cutaneous reflexes was found in both stroke and control subjects with stimulation of each nerve, but responses were blunted in stroke. Reflex reversal in tibialis anterior (TA) at heel strike with SP nerve stimulation was present in both groups. Notably, SR nerve stimulation produced facilitation during the swing-to-stance transition in the TA and suppression of MG in the MA leg during stance. CONCLUSIONS Interlimb cutaneous inputs may access coordinated reflex pathways in the MA limb during walking after stroke. Importantly activation in these pathways could provoke responses to counter foot drop during swing phase of walking. Additionally, our data support the perspective that there is no "unaffected" side after stroke and that caution should be used when interpreting the LA side as "control" after stroke. SIGNIFICANCE The presence of functionally-relevant interlimb cutaneous reflexes in the MA leg presents a substrate that may be strengthened by rehabilitation.
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Affiliation(s)
- E Paul Zehr
- Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, BC, Canada.
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Abstract
During rhythmic movement, arm activity contributes to the neural excitation of leg muscles. These observations are consistent with the emergence of human bipedalism and nonhuman primate arboreal quadrupedal walking. These neural and biomechanical linkages could be exploited in rehabilitation after neurotrauma to allow the arms to give the legs a helping hand during gait rehabilitation.
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Chang MD, Shaikh S, Chau T. Effect of treadmill walking on the stride interval dynamics of human gait. Gait Posture 2009; 30:431-5. [PMID: 19656682 DOI: 10.1016/j.gaitpost.2009.06.017] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2008] [Revised: 05/12/2009] [Accepted: 06/08/2009] [Indexed: 02/02/2023]
Abstract
Metronomic walking has been found to diminish the statistical persistence intrinsic to the stride interval time series of human gait. Since treadmill walking (TW) possesses a similar form of external pacing, we proposed to study the disruptions in the natural neuromuscular rhythms of gait during TW. Treadmill walking is a widespread rehabilitative tool, however, its effect on an individual's stride dynamics is not well understood. To better elucidate potential effects, we tested the hypothesis that TW without handrails would diminish the statistical persistence in an individual's stride interval time series. The scaling exponent (alpha) was employed in this study as a measure of the statistical persistence of the stride interval time series. Sixteen able-bodied young adults (mean age: 23.3+/-3.3 years) were instructed to walk at a self-selected comfortable pace for 15 min in three different conditions in a randomized order: (1) overground walking, (2) TW without holding a handrail (NoRail) and (3) TW while holding a front handrail (Rail). The alpha did not differ significantly between the overground and NoRail conditions (P>0.5). However, the alpha of the Rail condition (alpha=0.92+/-0.10) differed significantly from both the overground (alpha=0.83+/-0.06; P<0.015) and NoRail conditions (alpha=0.82+/-0.08; P<0.01). In contrast, stride interval variability did not change between walking conditions (P>0.5). These findings indicate that comfortable-paced TW does not diminish the intrinsic stride dynamics of human gait.
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Affiliation(s)
- Matthew D Chang
- Bloorview Research Institute, 150 Kilgour Road, Toronto, ON, Canada M4G 1R8
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