The principle of action potential conduction velocity measurement in the nerve stem is that because the membrane potential of the nerve stem is between -20 mV and 100 mV, when an external current stimulus is applied to depolarize the local area, an action potential is generated when the critical point for action potential release is reached, and the depolarized local current depolarizes the inactive areas located on both sides of the active area and continues in this order, so that the nerve impulse propagates from a site of external stimulation of the nerve stem to both ends simultaneously. from one part of the nerve stem to both ends simultaneously. However, under physiological conditions, physiological impulses originating from the anterior horn cells of the spinal cord or sensory endings are conducted only in one direction. In myelinated nerves, action potential conduction proceeds in a hopping fashion between the nerve node and the node, so that nerve conduction is faster.