Standardisation of the electrical elicitation of the human flexor reflex.

The threshold and latency of the human flexor reflex were recorded by different kinds of electrical stimuli in order to find the optimal stimulus, defined as the lowest amount of currency and the shortest possible duration. Stimulation was given over the posterior tibial nerve of the foot. The reflex response was recorded from the tibialis anterior muscle and the number and duration of the pulses and the inter-phase interval were varied. A train of five square wave pulses with a duration of 0.5 ms separated by 1 ms were found most suitable in quantitative studies of the reflex. Twenty-four normal persons were investigated in this way as a basis for normal values. The day-to-day variations of the reflex were small in normal subjects.