Moderate exercise not only has a positive impact on overall health, but also can serve as a rather accessible preventive measure for maintaining health, particularly the cardiovascular system health. The study aimed to assess the cardiovascular system adaptive capacity in chronic heart failure with moderate exercise in different age groups. Moderate exercise was induced in 6- and 19-month-old rats by forced swimming in a water bath at 32–34°C. During training, chronic heart failure was induced by intraperitoneal administration of the anthracycline antibiotic doxorubicin (Teva) at a cumulative dose of 15 mg/kg, divided into 6 injections over 14 days. Serum levels of brain natriuretic peptide and corticosterone were determined by ELISA every seven days throughout the experiment in all rats. It was found that with chronic heart failure and moderate exercise, myocardial adaptation was significantly higher in both age groups. It was most pronounced in aging rats, as evidenced by the dynamic changes of serum natriuretic peptide levels throughout the experiment. In both fertile-age and aging rats, the body's adaptive capacity in the event of cardiac dysfunction with moderate exercise is higher than in the absence of training.