Rhythmic Regulation of Blood Circulation in Humans during Progressively Increasing Physical Activity

The article addresses the problem of studying the reactivity of the human circulatory system to a progressively increasing physical activity, as certain mechanisms of circulatory regulation in response to various stimuli remain insufficiently studied. The method of continuous noninvasive arterial pressure (CNAP) recording combined with simultaneous ECG signal recording allows for a more precise assessment of circulatory regulation by analyzing changes in the duration of cardiointervals (RR), inter-systolic intervals (SSTI), and inter-diastolic intervals (DDTI) at rest and during the incremental exercise test on a cycle ergometer. To assess the variability of these time intervals, Poincaré plots were constructed, from which standard geometric indices were calculated: SD1 (short-term variability), SD2 (long-term variability), and S (total variability). This approach enables a comparison of the variability of autonomic circulatory regulation and hemodynamic parameters, revealing the features of the regulatory responses of cardiac contractions and hemodynamic reactions to physical exercise. The obtained results indicate that the variability of RR, SSTI, and DDTI intervals coincides at rest, reflecting the synchronous functioning of the circulatory system components in the absence of load. However, differences in the variability of neurogenic and hemodynamic regulation become detectable as soon as the onset of the exercise response and remain statistically significant with further incremental cycle exercise. Thus, it has been shown that during adaptation of the human circulatory system to a mild cycle ergometer exercise, specifically at the transitional step from lower to higher loads (until steady-state attainment), the variability dynamics of RR intervals does not correspond to that of SSTI and DDTI.