Mechanism of the Viscoelastic Deformation of Collagenous Tissue

Abstract

THE purpose of the experiment reported here was to examine the striking observation of Rigby et al.¹ that for collagenous tissue the thermally activated process controlling mechanical relaxation changes abruptly at the body temperature. For rat tail tendon it was observed¹ that below 37° C the process is entropy activated: the activation energy ΔH=0. Above 37° C, Rigby et al.¹ conclude that ΔH is large although their experiment does not yield a quantitative result. The result is paradoxical in two ways. First, entropy activation, although feasible conceptually, is essentially unknown in nature. Second, is it plausible that the rate process should change in such a profound way right at the body temperature? We have now resolved both paradoxes.