Comments on the Mechanism of Force Generation in Striated Muscles

Abstract

HUXELY and Simmons¹ have described the tension response of frog muscle to very rapid small changes of length in the following way (Fig. 2 of ref. 1). The tension changes simultaneously with the length change from a starting value T₀ to a new T₁ and this change is then reversed by a fast non-exponential recovery to a value T₂ followed by a very much slower recovery to a value near the original tension. They pointed out that the speed of the tension recovery varies widely, which they explained by a theory which predicts a strong dependence of the rate constant of the quick phase of the tension recovery on the amplitude and direction of the imposed length change. But this notion is not supported by their results, and here I suggest that it is more appropriate to describe the responses as the sum of two exponentials of different rate constant, the varying proportion of these giving the observed changes of speed.