Active tension changes in frog skeletal muscle during and after mechanical extension

Abstract

Isolated frog sartorious muscle at 4°C has been used to study the phenomenon whereby tetanically stimulated muscle, subjected to a mechanical extension, yields an active tension which is greater than that obtained during an isometric contraction in which the muscle is stretched prior to stimulation. The excess tension magnitude and decay with time depend upon the total muscle length. After stimulation ceases the excess tension does not persist over a time appreciably longer than that needed for the normal isometric tension to disappear. No persistent excess tension could be seen from stretches applied after stimulation had ceased but before the active tension had fully decayed.