The F-wave is an action potential that is evoked intermittently from a muscle by a supramaximal electrical stimulation of the nerve that is caused by the antidromic activation of motor neurons. The F-wave action potential is approximately 1–5 % that of the M-wave and has a variable configuration. Its latency is longer than that of the M-wave and is variable

F-wave studies evaluate the conduction of motor axons proximal to the stimulation site. During routine studies, the antidromic potential reaches and depolarizes the cell body. The depolarization is conducted back to the axon, and a new action potential is generated, which conducts to the muscle. This response is the F-wave.