Reciprocal inhibition of the H-reflex in the forearm: methodological aspects.

Reciprocal inhibition of the H-reflex in the wrist flexors elicited by stimulation of the radial nerve provides insight into the pathophysiology of different kinds of dystonia and may become a diagnostic tool for some movement disorders. Some of the results have been conflicting, however, owing presumably to differences in the technique. The present study in normal subjects shows that the amount of inhibition increases with decreasing amplitude of the unconditioned H-reflex and with increasing intensity of the radial nerve stimulus. Duration of the stimulus is important: stimuli of short duration are ineffective, and stimuli of long duration produce inconsistent inhibition.