PhD, Associate Professor A.B. Petrov^{1, 2}
Applicant A.M. Firago¹
PhD, Associate Professor A.N. Denisenko¹
Dr. Hab., Professor N.Yu. Nerobeev¹
PhD, Associate Professor L.V. Nerobeeva^3
1Lesgaft National State University of Physical Education, Sports and Health, St. Petersburg
²Almazov National Medical Research Centre, St. Petersburg
³St Petersburg University, St. Petersburg

Abstract
Heart rate (HR) responds to physical activity (PA) not only by increasing the frequency, but also by changing the difference between adjacent cardio intervals (CI). This variability is also an indicator of load tolerance.
Objective of the study was to reveal the dynamics of differences in cardio intervals of skilled wrestlers during different periods of increasing physical activity.
Methods and structure of the study. A group of active athletes (24 people) was examined: Masters of Sports - wrestling (sambo, judo, universal fight). The stress test (veloergo-) was carried out according to an individual RAMP protocol with an increment of 30 W. The digitized electrocardiogram was converted into a sequential time series of cardio intervals. We studied the dynamics of differences between adjacent cardio intervals (pX): prestart - 30 seconds preceding the start of ergometry; start - 30 seconds from the start of rotational locomotion with a load of 50 W; the entire load period - every minute. The pX values, where p is the % of differences from the total number in the array, X is the value of the difference between adjacent cardio intervals in ms, were calculated in Microsoft Excel tables. Since the data distribution differed from normal, they were presented as a percentile (Pc) series (25-Me-75).
Results and conclusions. The achievement of the limiting level of physical activity is manifested by: an increase in the participation of short intervals (NN2-4-6): the maximum increase by 1 min of load, a high stable level for 1-3 min, a slow decrease by 9 min; actually stable participation of the central intervals; a more pronounced drop to 1 min load, stability for 1-3 min and a smooth upward trend towards 9 min from long intervals.
The revealed regularities characterize the features of the formation of tolerance to increasing physical load in wrestlers of various specializations. The dynamics of tolerance probably carries markers of individual and optimal fitness.

Keywords: bicycle ergometry, variability of RR-intervals.

References

1. Golubeva N.K., Petrov A.B., Shuliko Yu.V. et al. Vliyaniye trenirovochnoy raboty na adaptatsionnyye kharakteristiki organizma [Influence of training work on the adaptive characteristics of the organism]. Teoriya i praktika fizicheskoy kultury. 2020. No. 11. p. 100.
2. Lapkin M.M., Mikhailov V.M., Petrov A.B. et al. Patent 2613937 RF. Sposob opredeleniya potentsialnogo urovnya fizicheskoy rabotosposobnosti pri submaksimalnom nagruzochnom testirovanii [Patent 2613937 RF. A method for determining the potential level of physical performance during submaximal stress testing]. No. 2015136686; appl. 08.29.2015.
3. Lapkin M.M., Trutneva E.A., Petrov A.B. et al. Prognosticheskiy potentsial vremennógo ryada kardioritmogrammy stress-testa [The prognostic potential of the time series of the stress-test cardiorhythmogram]. Fiziologiya cheloveka. 2019. Vol. 45. No. 3. pp. 48-60.
4. Lapkin M.M., Birchenko N.S., Pokhachevsky D.A. et al. Prognosticheskiy potentsial nagruzochnoy kardioritmogrammy rannego adaptatsionnogo perioda [Prognostic potential of the load cardiorhythmogram of the early adaptation period]. Chelovek. Sport. Meditsina. 2018. No. 1 (18). pp. 46-59.
5. Pokhachevsky A.L., Lapkin M.M., Trutneva E.A. et al. Adaptatsionnyye mekhanizmy predelnoy rabotosposobnosti [Adaptation mechanisms of limiting performance]. Teoriya i praktika fizicheskoy kultury. 2021. No. 8. pp. 17-19.
6. Pokhachevsky A.L., Filipchenko A.I., Kulagin P.A. et al. Osobennosti formirovaniya fizicheskoy rabotosposobnosti v molodezhnoy vyborke [Features of the formation of physical performance in the youth sample]. Teoriya i praktika fizicheskoy kultury. 2022. No. 1. p. 41.
7. Pokhachevsky A.L., Abdullaeva K.G., Akulina M.V. et al. Osobennosti serdechnogo ritma v predstartovyy, nagruzochnyy i vosstanovitelnyy periody stress-testa [Features of the heart rhythm in the pre-start, load and recovery periods of the stress test]. Teoriya i praktika fizicheskoy kultury. 2019. No. 7. pp. 55-58.
8. Pokhachevsky A.L., Lapkin M.M., Mikhailov V.M. et al. Patent 2613921 RF. Sposob opredeleniya vosstanovitelnogo potentsiala u sportsmenov, razvivayushchikh aerobno-anaerobnuyu vynoslivost [Patent 2613921 RF. A method for determining the recovery potential of athletes developing aerobic-anaerobic endurance]. No. 2015137142; appl. 09.01.2015.