Journal
JOURNAL OF NEUROPHYSIOLOGY
Volume 103, Issue 3, Pages 1262-1274Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/jn.00852.2009
Keywords
-
Categories
Funding
- Spar Nord Foundation
- Obel Family Foundation
Ask authors/readers for more resources
af Klint R, Cronin NJ, Ishikawa M, Sinkjaer T, Grey MJ. Afferent contribution to locomotor muscle activity during unconstrained over-ground human walking: an analysis of triceps surae muscle fascicles. J Neurophysiol 103: 1262-1274, 2010. First published December 23 2009; doi: 10.1152/jn.00852.2009. 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 degrees 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.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available