HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 99/4/2000    most recent 01315.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Javan, B. Articles by Zehr, E. P. Search for Related Content PubMed PubMed Citation Articles by Javan, B. Articles by Zehr, E. P.

REPORT

Short-Term Plasticity of Spinal Reflex Excitability Induced by Rhythmic Arm Movement

¹Rehabilitation Neuroscience Laboratory and ²Centre for Biomedical Research, University of Victoria, Victoria; and ³Human Discovery Science, International Collaboration on Repair Discoveries, Vancouver, British Columbia, Canada

Submitted 4 December 2007; accepted in final form 26 January 2008

Rhythmic arm movement reduces Hoffmann (H)-reflex amplitudes in leg muscles by modulation of presynaptic inhibition in group Ia transmission. To date only the acute effect occurring during arm movement has been studied. We hypothesized that the excitability of soleus H-reflexes would remain suppressed beyond a period of arm cycling conditioning. Subjects used a customized arm ergometer to perform rhythmic 1-Hz arm cycling for 30 min. H-reflexes were evoked before, during, and after arm cycling via stimulation of the tibial nerve in the popliteal fossa. The most important finding was that the H-reflex amplitudes were significantly suppressed during and 20 min after arm cycling had been terminated. Thus remote arm cycling can induce adaptive plasticity in the soleus H-reflex pathway that persists beyond the period of conditioning. In an additional experiment, the prolonged effect of arm cycling combined with cutaneous superficial radial (SR) nerve stimulation was investigated. Cutaneous stimulation cancelled the prolonged suppression of H-reflex amplitude induced by arm cycling. Because SR nerve stimulation facilitates soleus H-reflex via reducing the level of Ia presynaptic inhibition, persistence in presynaptic inhibitory pathways is suggested as the underlying neural mechanism. The simplest explanation of this observation is plateau potential-like behavior of interneurons mediating presynaptic inhibition of Ia afferent transmission.