Features of blood circulation in young men during adaptation to physical load

The objective of this paper is to identify the mechanism of urgent adaptation of cardiac output and its components under increasing physical load in young men with different levels of physical activity depending on features of blood circulation. Materials and Methods. The study enrolled young men, who were divided into groups according to the type of physical activity and blood circulation. The increasing physical load was simulated on a veloergometer (0.5; 1.0; and 1.5 watts of power for every kilogram of body weight). Before and during physical load the record of differential rheograms (W. Kubicek method) was carried out. The records were used to define the indices of cardiovascular system. Results. The young men demonstrated hypo-, eu- and hyperkinetic circulation types, depending on the level of physical activity. Under increasing physical load significant increase in cardiac output was registered. It was physiologically justified and aimed at maintaining optimal oxygen conditions. The increase in cardiac output in young men with high physical activity of eukinetic and hypokinetic circulation types was accompanied by a rising heart rate and stroke volume. The mechanism of significant increase in stroke volume under increasing physical load in groups of young men with eukinetic and hypokinetic circulation types is due to the fact that their diastolic and systolic left ventricular volumes are larger than those in young men of other groups. Therefore, under physical load both of these volumes are significantly reduced; it determines the increase in stroke volume. Conclusion. The formation of blood cardiac output under increasing physical load in groups of young men with different physical activity and circulation type was determined by functional abilities of the heart to increase stroke volume. The most effective mechanism for manifestation of blood cardiac output urgent adaptation to physical load was demonstrated in young men with high physical activity and hypo- and eukinetic types of circulation.