[The activation and mechanical determinants of the rate of isometric relaxation of the heart muscle].

In experiments with sequential loads, the relative velocity of cardiac muscle relaxation was found to be affected by the calcium ions concentration, velocity of shortening and by the terminal systolic length. Mechano-chemical dissociation played a major role, too, in the relaxation determination. The shifts in mechanical relaxation seem to be based on the cooperation phenomena in the troponine regulation of contraction and relaxation.