'Train of four' is characteristically used in concern with

Train-of-four stimulation devotes four successive 200 - ms stimuli in 2 s (2 Hz). The twitches in a train-of-four pattern progressively fade as relaxation increases. The ratio of the responses to the first and fouh twitches is a sensitive indicator of nondepolarizing muscle paralysis. Disappearance of the fouh twitch represents a 75% block, the third twitch an 80% block, and the second twitch a 90% block. Clinical relaxation usually requires 75-95% neuromuscular blockade. Ref: KD Tripathi 8th ed.