Supernormal excitability of human sensory fibers after ischemia

Weak electrical stimuli were applied to sensory fibers of the median nerve at the wrist, and the ascending action potentials were recorded at the elbow. This was done with or without a preceding conditioning stimulus to test for supernormal excitability to the second stimulus. In the resting nerve, supernormal excitability was present from 3 to 20 msec after a conditioning shock. After a period of ischemia, excitability was both exaggerated and prolonged. This observations confirms the presence in sensory fibers of a phenomenon previously described in motor fibers.