The antidromic impulse associated to the ephaptic response can produce a recurrent wave (Fe). Its latency, which is longer than that of the F wave, will augment if the site of stimulation is remote from the muscle. It is therefore a direct-indirect response. The 'Fe' wave is similar to the 'S' response described by Thorne, but the gamma-loop is not implicated. It can be misinterpreted as a desynchronized F wave.
Aged Electric Stimulation