The influence of the rate of rigor state development on its tension in single muscle fibre.

The rigor tension and stiffness of glycerinated fibres from rabbit psoas muscle were found to vary markedly in dependence on the rate of substitution of the solutions in the experimental chamber. The maximum value of rigor tension, which is close to that activated by Ca2+ with pCa4, was obtained at the slow development of rigor in the absence of Ca2+ ions. The observed dependence is assumed to be due to the different degrees of removal of the 'slack' in fibres, which may be contributed by compliant ends of the preparation. A new method allowing to obtain rather reproducible values of rigor tension is proposed.