If a muscle twitch is 0.2 s long, it will first begin to show sum mation upon repetitive stimulation at a frequency of about
A) 2 Hz
B) 5 Hz
C) 20 Hz
D) 50 Hz
E) 500 Hz

Question

Quizplus · Accepted Answer

Muscle twitch summation begins when the frequency of stimulation is such that a new stimulus is applied before the previous twitch has completely relaxed. Since a twitch is 0.2 seconds long, the muscle will start to show summation at frequencies higher than 1/0.2 = 5 Hz, because at 5 Hz or higher, a new stimulus occurs before the muscle has fully relaxed from the previous twitch, leading to summation.

If a Muscle Twitch Is 0