abstract:The nociceptive flexion reflex, or nociceptor flexion response (NFR) or RIII reflex is a withdrawal reflex involving numerous spinal cord synapses in response to activation of A-delta nociceptors (fast pain signalling nerve fibers). The NFR is measured by using an electromyogram to monitor the muscle activity in the upper leg (biceps femoris) while applying increasing electrical stimulation to the lower leg (sural nerve) on the same side of the body.