The behaviour of a mammalian muscle during sinusoidal stretching

Abstract

Tension changes were recorded in tetanized and passive cat soleus muscles during sinusoidal stretching at frequencies between 0-25 and 12-5 c/s. The muscle tension varied in an approximately sinusoidal manner during sinusoidal stretching. The tension record showed an angular advance on muscle length. A method of measuring mean angular advance in non-linear systems is described. Resistance to lengthening increased with increasing fequency of stretching in tetanized muscle. The elastic stiffness increased more rapidly than the viscous stiffness with increasing fequency, so that the angular separation between length and tension became smaller at the higher frequencies. The elastic stiffness of the tetanized muscle declined with increasing stretch amplitude, and the mean angular advance of tension became larger. The viscous stiffness increased at the higher frequencies in passive muscle, and the mean angular advance of tension on length was correspondingly increased.