M.D., D.Sc. (Medicine), Professor A.L. Pokhachevskiy^{1, 2}
Postgraduate I.V. Sukhinin²
Postgraduate D.V. Samarskiy²
Associate Professor S.S. Ssorin³
PhD, Professor Yu.V. Shuliko^4
1I.M. Sechenov First MSMU MOH Russia (Sechenovskiy University)
²RyazSMU, Ryazan
³The Academy of the FPS of Russia
⁴State Lesgaft University of Physical Culture, Sports and Health

Key words: physical activity, stress test, heart rate.

Introduction. The study of the interrelationships of physical activity tolerance (FN) and the rate of change in the duration of cardiointervals (CI) during the stress test is likely to reveal prognostic markers of the formation of physical performance.
The aim of the study is to identify significant correlations between markers of FN tolerance and the rate of change in the duration of CI during various periods of stress test in a group of athletes qualified for CMS, MS cyclic sports.
Methodology and organization. The sequential time series (BP) of cardio intervals (CI) of the bicycle ergo-stress test was divided into periods: pre–start (PS) – 30 seconds before the start of the test; start (ST) - 30 seconds from the start of locomotion (50 watts); then minute-by-minute loading, recovery periods. Nonparametric criteria (Statistica 10.0) were used for statistical processing. The BP of each of the periods was linearly modeled: Y=aX+b, where X is the sequence number of CI, Y is the duration of CI, "a" is the model parameter characterizing the rate of variability of BP and "b" is the model parameter determining the constant component [1, 2].
Results and discussion. The start period, like the PS, does not actually differ in a large variety of connections, but is characterized by an inverse pattern, when a high rate of increase in heart rate corresponds to its lower values at 1 and 2 minutes of load. Unlike PS and CT, the 1st minute of the load has a high prognostic potential, which is manifested by a statistically significant positive relationship with the 3rd minute of the load (0.55), more intense – with the second minute of recovery (0.63) and the maximum load level (0.61). At the same time, the lower the rate of heart rate growth, the lower it is at the 3rd, 4th (0.41) loading minute, less at the 2nd minute of recovery and the higher the maximum level of the transferred load. The second minute of the load shows a significantly lower potential, but a stronger relationship (0.68) with the 2 minute of recovery, when a lower rate of heart rate growth under load corresponds to a higher recovery rate. The third loading minute is manifested by virtually equal connections with the 2nd and 3rd (0.5 each) minutes of recovery, as well as with the maximum load tolerance (0.48). At the same time, the higher the rate of heart rate growth during this period, the lower it is at the 2nd, 3rd minute of recovery and the lower the transferred load. The 4th minute of the load is characterized by an increasing relationship with the recovery period: from -0.52 at the 1st minute to -0.81 at the 4th. The revealed inversion (relative to the above-discussed links of loading speeds with recovery speeds) is probably related to the heterogeneity of the examined group in terms of the level of tolerance of FN. During the recovery period, attention is drawn to the moderate positive relationship of the 1st minute with the 4th (0.55) in the complete absence of those with the 2nd and 3rd minutes of the same period. Probably, the present phenomenon has a systemic adaptive meaning when the inhibitory processes prevailing at the 1st minute, due to the end of the load, come into conflict with the ongoing humoral processes during the 2nd, 3rd minutes (metabolism of buffered CO2 and protons during the restoration of oxygenation). In addition, the positive moderate relationship of the 2nd minute of recovery with the transferred load (0.61) deserves attention, when a higher recovery rate corresponds to a higher maximum of the already transferred FN.
Conclusions. The prediction of the rate of variability of the load heart rate over the period of PS and ST is not possible. 1-4 minutes of loading are acceptable for this purpose, but each of them has its own characteristics that determine the time and strength of the relationship. The first minute is optimal for the forecast of the same period, the 2nd minute of recovery, as well as the maximum of the transferred load, the 2nd minute - for the forecast of the 2nd minute of recovery, the 3rd - for the forecast of the 2nd, 3rd minute of recovery and the load maximum, the 4th – for the forecast of 1, 4 minutes recovery.

Literature

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