Fig: Recurrent discharge of motoneurones
With supramaximal electrical stimulation of the peripheral nerve, electrical impulses propagate both orthodromically to the muscle (solid arrorw) and
antidromically to the motoneurones in the spinal cord (broken arrow). Antidromic activation can re-excite a small number of these motoneurones.
The reflected impulses then travel orthodromically to the muscle. These late muscle responses are know as F waves when measured in the EMG