Afferent contribution to locomotor muscle activity during unconstrained overground human walking: an analysis of triceps surae muscle fascicles

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Title Afferent contribution to locomotor muscle activity during unconstrained overground human walking: an analysis of triceps surae muscle fascicles
Author Klint, R. af; Cronin, Neil; Ishikawa, M.; Sinkjaer, T.; Grey, M. J.
Journal Name Journal of Neurophysiology
Year Published 2010
Place of publication USA
Publisher American Physiological Society
Abstract Plantar flexor series elasticity can be used to dissociate muscle–fascicle and muscle–tendon behavior and thus afferent feedback during human walking. We used electromyography (EMG) and high-speed ultrasonography concomitantly to monitor muscle activity and muscle fascicle behavior in 19 healthy volunteers as they walked across a platform. On random trials, the platform was dropped (8 cm, 0.9 g acceleration) or held at a small inclination (up to ±3° in the parasagittal plane) with respect to level ground. Dropping the platform in the mid and late phases of stance produced a depression in the soleus muscle activity with an onset latency of about 50 ms. The reduction in ground reaction force also unloaded the plantar flexor muscles. The soleus muscle fascicles shortened with a minimum delay of 14 ms. Small variations in platform inclination produced significant changes in triceps surae muscle activity; EMG increased when stepping on an inclined surface and decreased when stepping on a declined surface. This sensory modulation of the locomotor output was concomitant with changes in triceps surae muscle fascicle and gastrocnemius tendon length. Assuming that afferent activity correlates to these mechanical changes, our results indicate that within-step sensory feedback from the plantar flexor muscles automatically adjusts muscle activity to compensate for small ground irregularities. The delayed onset of muscle fascicle movement after dropping the platform indicates that at least the initial part of the soleus depression is more likely mediated by a decrease in force feedback than length-sensitive feedback, indicating that force feedback contributes to the locomotor activity in human walking.
Peer Reviewed Yes
Published Yes
Alternative URI http://dx.doi.org/10.1152/jn.00852.2009
Copyright Statement Copyright 2010 American Physiological Society (APS). Self-archiving of the author-manuscript version is not yet supported by this publisher. Please refer to the journal link for access to the definitive, published version or contact the authors for more information.
Volume 103
Issue Number 3
Page from 1262
Page to 1274
ISSN 0022-3077
Date Accessioned 2010-09-02
Language en_AU
Faculty Griffith Health Faculty
Subject Biomechanics; Motor Control; Sensory Systems
URI http://hdl.handle.net/10072/34092
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1x

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