Cardiovascular system, an organic system consisting of the heart and blood vessels, through which human blood circulates. The work of this system can be divided into 2 periods: the systole period and the diastole period. The systole period includes the period of the cardiac cycle in which the heart ventricles contract and eject blood. The right ventricle is responsible for ejecting venous blood into the pulmonary artery, while the left ventricle is responsible for ejecting arterial blood into the aorta. During systole, the blood pressure in the ventricles rises, and this is crucial for the opening of the valve between the ventricles and the pulmonary artery, and for the outflow of blood from the ventricle itself. Unlike systole, diastole means the period of release or relaxation of the heart muscle within the cardiac cycle. The beginning of diastole begins with the opening of the valves between the atria and ventricles. For adequate maintenance of this system, and in order to prevent numerous cardiovascular diseases, exercise, i.e. aerobic and anaerobic training, is of great importance. Skeletal muscles that are activated by exercise cause numerous changes in the cardiovascular system. Changes are mainly expressed in blood pressure values, heart rate and cardiac output. In addition to it's benefits, physical activity also has it's risks, so proper dosage and adjustment of exercises are important to avoid further complications.