Phase-dependent modulation of the soleus H-reflex induced by rhythmic arm cycling




De Ruiter, Geoffrey Charles

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Rhythmic arm cycling is known to suppress the Hoffmann (H-) reflex in the soleus muscles of stationary legs; however, it is still unclear if this suppression is modulated by the phase of movement in the cycle path. In the present study we investigated phase-dependent modulation of the Sol H-reflex induced by rhythmic arm cycling. Modulation of the Soleus H-reflex was examined at 12 phases of the cycle path in 4 conditions; static arm positioning, as well as 3 arm cycling conditions, bilateral, ipsilateral and contralateral. H-reflexes were evoked and recorded at constant motor wave amplitudes across the conditions. Suppression of Sol H-reflex amplitude was dependent (main effect p<0.0001) upon the phase of movement during arm cycling, but not during static positioning. Results suggest that locomotor central pattern generators may contribute to the phasic reflex modulation observed in this study.



phase, dependent, Ipsilateral, Contralateral, Bilateral, Rhythmic, arm, cycling