To induce FвЂђwaves, transcutaneous peripheral nerve stimulation (PNS) is used, which activates nerve branches via transcutaneous electrodes over the nerve branches. The FвЂђwave is a motor response induced by electrical stimulation of peripheral nerves via the antidromic firing of motor nerves, which reflects the motoneuron excitability. (C), #1-in motor axons conducting orthodromic impulses of voluntary drive, voluntary and antidromic impulses will collide #2-reflex response which travels along motor axons cleared by the collision described in point #1 will contribute to the V-wave #3-presynaptic inhibition can influence afferent input to the motoneuron. (B), #1-a small number of motoneurons may discharge to produce F-waves after antidromic impulses reach their soma #2-at rest, F-waves are likely to be limited to large motoneurons due to reflex activation of smaller motoneurons and collision with the antidromic volley prior to the soma. (A), #1-electrical stimulus evokes a single afferent volley which recruits motoneurons for the H-reflex according to the size principle #2-presynaptic inhibition can influence afferent input to the motoneuron #3-tendon tap evokes multiple volleys which arrive at the motoneuron over 25 ms. Only the most critical elements are labeled so see text for a complete description of the factors which can influence each response.

Schematic representation of the volleys and pathways involved in the production of the H-reflex, tendon jerk, F-wave, and V-wave.

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