Considering the latent period of muscle twitch to be 10 ms, contraction time 40 ms and relaxation time 50 ms, what will be the tetanizing frequency for this muscle?
(A) 25 Hz (B) 50 Hz (C) 100 Hz (D) 75 Hz
(A) Ans: A. 25 HzStimulation frequency at which summation of contractions occurs -Determined by twitch duration of the paicular muscle under study.Example:If twitch duration = 10 ms.Frequencies less than 1/10 ms (100/s) - Cause discrete responses interrupted by complete relaxation.Frequencies greater than 100/s cause summation.Tetany:Continuous contraction of muscle fibers, without latent period & relaxation time.Hence tetanizing frequency depends only on contraction time, i.e. twitch duration.Twitch duration = 40 milliseconds = 0.04 secTetanizing frequency = 1/0.04 = 25 Hz