Effect of rhythmic arm movement on soleus H-reflex amplitudes in the less and more affected legs after stroke




Barzi, Yasaman

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Rhythmic arm cycling suppresses the soleus H-reflex amplitude in stationary legs in neurologically intact (NI) participants. It has been suggested that interlimb pathways connecting cervical and lumbosacral spinal cord are responsible for modulating the reflex excitability. After stroke, stretch reflex and its electrical analogue the H-reflex become hyperactive. The purpose of this study was to examine the effect of arm cycling on the H-reflex amplitude in the stationary legs after stroke. It was hypothesized that rhythmic arm movement would suppress the H-reflex amplitudes in the Iegs after stroke. Sixteen stroke participants performed bilateral arm cycling at 1Hz and at the highest frequency possible they could maintain. Additionally, thirteen age-matched neurologically intact individuals participated as a control group. Tibial nerves were stimulated to evoke H-reflexes simultaneously in both legs. M-wave, H-reflex (M-H) recruitment curves (RC) were collected during arm cycling and with arms stationary. Four variables (i.e.. M-H slope, H at threshold. Hmax, and 50% Hmax] obtained from the ascending limb of the M-H RC were compared across conditions. Results showed that the general effects of arm cycling in suppressing H-reflex size are preserved after stroke. However, effects after stroke were limited in that arm cycling did not affect the whole recruitment curve similarly, as it does in the NI population. Overall the results suggest that incorporation of rhythmic arm movement in rehabilitation paradigms after stroke might be helpful in suppression of hyperactive reflexes in the legs and therefore assist in locomotion.



locomotion, limbs, arm cycling, reflexes, interlimb pathways, stroke, recovery, neural coupling