Contribution of afferent feedback and descending drive to human hopping

Abraham T Zuur, Jesper Lundbye-Jensen, Christian Leukel, Wolfgang Taube, Michael J Grey, Albert Gollhofer, Jens Bo Nielsen, Markus Gruber

Research output: Contribution to journalArticle

57 Citations (Scopus)

Abstract

During hopping an early burst can be observed in the EMG from the soleus muscle starting about 45 ms after touch-down. It may be speculated that this early EMG burst is a stretch reflex response superimposed on activity from a supra-spinal origin. We hypothesised that if a stretch reflex indeed contributes to the early EMG burst, then advancing or delaying the touch-down without the subject's knowledge should similarly advance or delay the burst. This was indeed the case when touch-down was advanced or delayed by shifting the height of a programmable platform up or down between two hops and this resulted in a correspondent shift of the early EMG burst. Our second hypothesis was that the motor cortex contributes to the first EMG burst during hopping. If so, inhibition of the motor cortex would reduce the magnitude of the burst. By applying a low-intensity magnetic stimulus it was possible to inhibit the motor cortex and this resulted in a suppression of the early EMG burst. These results suggest that sensory feedback and descending drive from the motor cortex are integrated to drive the motor neuron pool during the early EMG burst in hopping. Thus, simple reflexes work in concert with higher order structures to produce this repetitive movement.

Original languageEnglish
Pages (from-to)799-807
Number of pages9
JournalThe Journal of Physiology
Volume588
Issue number5
Early online date26 Feb 2010
DOIs
Publication statusPublished - Mar 2010

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