Within-step modulation of leg muscle activity by afferent feedback in human walking

Authors

  • Richard af Klint,

    1. Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7D, DK-9220 Aalborg, Denmark
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  • Jens Bo Nielsen,

    1. Department of Neuroscience & Pharmacology and Department of Exercise & Sport Sciences, University of Copenhagen, Blegdamsvej 3, The Panum Institute 24.6, DK-2200 Copenhagen, Denmark
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  • Jonathan Cole,

    1. Centre for Postgraduate Medical Research and Education, University of Bournemouth and Poole Hospital, UK
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  • Thomas Sinkjaer,

    1. Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7D, DK-9220 Aalborg, Denmark
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  • Michael J. Grey

    1. Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7D, DK-9220 Aalborg, Denmark
    2. Department of Neuroscience & Pharmacology and Department of Exercise & Sport Sciences, University of Copenhagen, Blegdamsvej 3, The Panum Institute 24.6, DK-2200 Copenhagen, Denmark
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Corresponding author M. J. Grey: Department of Neuroscience & Pharmacology and Department of Exercise & Sport Sciences, University of Copenhagen, Blagedamsvej 3, The Panum Institute 24.6, DK-2200 Copenhagen, Denmark.  Email: mgrey@mfi.ku.dk

Abstract

To maintain smooth and efficient gait the motor system must adjust for changes in the ground on a step-to-step basis. In the present study we investigated the role of sensory feedback as 19 able-bodied human subjects walked over a platform that mimicked an uneven supporting surface. Triceps surae muscle activation was assessed during stance as the platform was set to different inclinations (±3 deg, ±2 deg and 0 deg rotation in a parasagittal plane about the ankle). Normalized triceps surae muscle activity was significantly increased when the platform was inclined (2 deg: 0.153 ± 0.051; 3 deg: 0.156 ± 0.053) and significantly decreased when the platform was declined (−3 deg: 0.133 ± 0.048; −2 deg: 0.132 ± 0.049) compared with level walking (0.141 ± 0.048) for the able-bodied subjects. A similar experiment was performed with a subject who lacked proprioception and touch sensation from the neck down. In contrast with healthy subjects, no muscle activation changes were observed in the deafferented subject. Our results demonstrate that the ability to compensate for small irregularities in the ground surface relies on automatic within-step sensory feedback regulation rather than conscious predictive control.

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