Dr. Med., Professor A.L. Pokhachevsky^{1, 2}
Dr. Med., Professor M.M. Lapkin²
PhD, Associate Professor E.A. Trutneva²
PhD, Professor D.S. Melnikov³
PhD, Associate Professor K.Y. Shubin^3
1I.M. Sechenov First MSMU MOH Russia (Sechenovskiy University), Moscow
²Ryazan State Medical University, Ryazan
³Lesgaft National State University of Physical Education, Sport and Health, St. Petersburg

Objective of the study was to conduct a stress test to study early heart rate variability and the effects of physical loads on the adaptive mechanisms that determine them.
Methods and structure of the study. Subject to the study were a mixed sample (n=28) of the apparently healthy individuals aged 18-22 years, who were subjected to a stress test (Lode Corival cycle ergometer) using an individual protocol. The electrocardiogram ("Poly-Spectrum", "Neurosoft") was transformed into successive RR intervals - cardiorhythmogram. The individual cardiorhythmogram rates in the load period were analyzed using linear mathematical models: prestart period (30 s) preceding the start of the ergometric test; start (30 s) – period from the start of the cyclic locomotions under the load of 50 W; 1st-3rd minutes into the test. The subjects’ load tolerance was measured by the difference between the maximum achieved and the power of the first stage. The spiroergometry (QuarkCPET: O2, CO2) was carried out throughout the entire stress test. Non-parametric criteria were used for statistical processing of the data obtained (Statistica 10.0).
Results and conclusions. The cardiorhythmogram in the load period was characterized by the maximum rate of shortening of RR intervals during the 1st minute, three-time shortening during the 2nd minute, and two-time shortening during the 3rd one. The prestart rates in the mixed, limited sample may not be the predictors of physical load tolerance, but predict the starting potential of the body quite accurately. The significant correlation with the markers of cardiorhythmogram in the load period is likely to predict an anaerobic threshold, which late onset is manifested in a higher load tolerance rate.

Keywords: heart rate, stress test, physical load.

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