The ‘plateau’ of full activity during a muscle twitch

Abstract

The active state of a muscle, after excitation by a single shock, rises rapidly to its full extent and then remains on a level or 'plateau' until relaxation begins to set in. The end of the 'plateau' is considerably earlier than the maximum of a normal twitch, but the method of quick stretches is not adequate to define it more accurately. In the method described in this paper a muscle is released at constant speed early in a twitch and the moment at which the tension begins to fall off is used as an index of the end of the 'plateau'. The decay of the active state, in a frog's sartorius at 0 degrees C, begins at a time after the stimulus which is about 0.4 to 0.5 of the time to maximum tension in a normal twitch.