Electrophysiological Evaluation Practice Test

Velocity is the distance traveled per unit time. In nerve conduction studies between two stimulation sites, you’re measuring how far apart those sites are and how long the impulse takes to travel from one site to the other. The time taken to traverse that segment is the difference in latencies, and the distance traveled is the difference in the stimulation-site distances. So the velocity is the distance difference divided by the latency difference: (D2 − D1) / (T2 − T1). This mirrors the basic speed formula and uses the exact segment the impulse travels. Using sums or reversing the ratio would not reflect the actual propagation along the segment and can give incorrect results (for example, adding distances or times isn’t measuring the travel over a single segment, and swapping numerator and denominator yields the inverse of velocity).