CYCLIC MODULATION OF THE H-REFLEX IN A WRIST FLEXOR DURING RHYTHMIC FLEXION-EXTENSION MOVEMENTS OF THE IPSILATERAL FOOT

In 12 subjects, each sitting on an armchair with the right forearm pro ne, the H-reflex elicited in the resting flexor carpi radialis muscle underwent cyclic excitability changes correlated with rhythmic flexion -extension movements of the ipsilateral foot (frequency of oscillation s between 1.5 and 2.5 Hz). During foot plantar flexion, the H-reflex u nderwent a clear-cut increase, the maximum facilitation falling, in mo st subjects, within the second half of that phase; then, a gradual red uction in size led the reflex amplitude back to the initial value at t he end of foot dorsal extension. If present also when the wrist and th e ankle are moved together, this facilitation should favour the in-pha se (isodirectional) association between movements and, conversely, hin der the anti-phase coupling.