[Prevention of disorders of myocardial contractile function under stress by the preliminary adaptation of animals to physical load].

Rats adapted to exercise (daily swimming for one hour over 30 days) and control animals were subjected to emotional-painful stress (EPS) according to the pattern of anxiety neurosis. It has been established that EPS decreases the amplitude as well as the rate of contractions and relaxations of the isolated papillary muscles of animals by 2-3 times and also reduces the resistance of the contractile function of the myocardium to the excess of Na+ and H+ ions, ousting Ca2+ from the sites of its binding in the sarcolemma. Adaptation to exercise exerts an opposite effect. The preliminary adaptation of animals prior to EPS prevents or limits the stress-related depression of the contractility of the myocardium and the diminution of its resistance to the factors replacing Ca2+. The preliminary adaptation to exercise may be used for preventing stress-related disorders of cardiac contractility.