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.

Simulation studies of contracting skeletal muscles during mechanical stretch

“…In any case, from our own experiments (Van Atteveldt and Crowe, 1980) it was seen that the tension changes due to the passive viscosity of the system were rather small compared to the total forces involved when active muscle was studied, so that possible non-linearities were of no consequence. The FSE was taken to be proportional to the extension of the SEE, i.e.…”

“…The simulated tension changes are compared with the experimental results presented in the previous article (Van Atteveldt and Crowe, 1980) and results of experiments on skeletal muscle presented by other authors (Edman et al, 1976;Edman et al, 1978a, b;Rack and Westbury, 1974;Sugi, 1972). * Received for publicatiort 22 May 1979.…”

“…It has been experimentally observed that, if the amount or speed of stretch are sufficiently large, the tension may reach a maximum value before the end of the ramp stretch (Van Atteveldt and Crowe, 1980;Sugi, 1972). This is known as the slip effect.…”

“…In the preceding paper (Van Atteveldt and Crowe, 1980) results were reported from experiments on isolated frog sartorious muscle subjected to controlled mechanical stretches of the ramp-and-hold type during tetanic contraction. The findings largely supported results carried out previously, on either single fibre preparations or bundles of fibres, with regard to such phenomena as the slip effect (Sugi, 1972) and excess tension after stretch (Edman et al, 1976(Edman et al, , 1978a.…”

“…In discussions of the possible mechanism by which these tension changes take place, it has been suggested that the cross bridges suffer elastic extensions which increase their contribution to the total tension but that attempted extension beyond an elastic limit causes mechanical breakage of the bridges (Van Atteveldt and Crowe, 1980;Sugi, 1972).…”