[The effect of submillisecond temperature jump on the mechanical tension of skinned muscle fibers of the frog in a state of rigor].

Modification of temperature jump method for skinned skeletal muscle fibres is described. The fibre heating was obtained applying the high-voltage high-frequency current impulse to the fibre after removing the surrounding solution. The method permits to obtain the heating for 15 degrees C in 0.25 msec. The temperature jump in rigorized fibre induced instantaneous drop of tension. This effect is probably induced by thermal expansion of contractile proteins in the fibre.