Professor, Dr.Hab., PhD A.G. Shchurov
Professor, Dr.Hab. G.G. Dmitriyev
Professor, Dr.Biol. B.V. Endal'tsev
Military Institute of Physical Culture, St. Petersburg

Abstract

This article provides information about the dynamics of recovery of the athletes' functional status after exercise under hyperbaric oxygenation. The data indicate that the regenerative processes that take place in the body after exercise under hyperbaric oxygenation proceed more efficiently. And in these circumstances, the indicators detected in the subjects at the end of the session indicated a more economical functioning of the body compared with the initial state.

Keywords: athletes, functional status, hyperbaric oxygenation, hyperoxia, physiological reserves.

Introduction. The study of the dynamics of recovery of the functional status of athletes after exercise is the issue of the day, which if solved will help carry out a number of tasks related to the training process, in particular, it will help obtain the scientifically validated recommendations on the use of various extra-training means.

Objective of the study was to substantiate the efficiency of hyperbaric oxygenation (HBO) when used to recover the athletes’ functional status after exercise.

Materials and methods. The idea that the dynamics of the functional status of athletes could be determined by the indicators reflecting the regulatory changes in the autonomic nervous system served as a premise for selecting research methods in this paper. Among such methods is a mathematical analysis of heart rate variability (HRV).

The HRV method is used to reveal the peculiarities of the regulatory effects of the nervous system on the heart, and thus, measure the parameters of the physiological reserves of the system of regulation of heart functions and functional status of the body in general. These indicators include: mode (Mo) of RR intervals, their variation range (dX), standard deviation of Normal-Normal (SDNN) and amplitude mode (AMo), as well as the Bayevskiy’s tension index (TI) of the regulatory systems, vegetative rhythm index (VRI), etc. [1, 3].

It should be noted that with the improvement of the athletes’ functional status, the values of the amplitude mode of RR intervals (AMoRR), TI, VRI and SDNN, their Mo and dX decrease [2, 3].

For the purpose of this research we conducted two series of studies. During the first series, we studied the dynamics of the functional status of athletes after exercise in normal conditions, during the second series - after exercise under hyperbaric oxygenation.

The experimental variables of the heart rate registered in the initial state were compared with those obtained during the subsequent stages of recovery after exercise in normal conditions and under hyperbaric oxygenation. In the latter case, the indices of the functional status of the body detected in the subjects 5 minutes after breathing oxygen under the conditions of increased pressure corresponded to the indices detected 25 minutes after exercise, since, in that case, oxygen breathing started 20 minutes after the end of exercise. Same 12 elite athletes (I Class or higher) participated in both series of the experiment. Physical exercise was performed on a cycle ergometer at the level of submaximal power to failure.

The HBO sessions were carried out in the upgraded flow-decompression chamber (FDC-2U) consisting of two sections and equipped with the oxygen supply system. The HBO mode is characterized by the following parameters: oxygen partial pressure (pO₂) – 0.20 MPa; exposure - 50 min; compression and decompression duration - 10 min.

Results and discussion. Initially, the quantitative indices of HRV (Table 1) testify that the predominance of the parasympathetic division of the autonomic nervous system over the sympathetic one in the heart rate regulation, low level of functioning of the sinus node and high functional status and adaptive capabilities of the subjects’ body. The heart rate parameters changed significantly after exercise.

The dynamics of the heart rate indices after exercise, when recovering in normal conditions, indicates that the RR interval variability decreases sharply 5 minutes after exercise. Thus, the mean values of Mo, dX, SDNN decrease significantly, while AMo, TI and VRI increase compared to the initial values.

As the subjects recover after exercise, all the quantitative indicators of the heart rate variability gradually return to their initial level. However, 25 minutes after exercise, there are still significant differences of almost all heart rate indices from their values ​​registered in the initial state, which testifies to major shifts in the body caused by exercise. At the 50th minute of recovery, a number of indicators of the RR intervals duration (dX, Mo, TI) reach their initial level. Other indicators need more time to recover to their initial values.

Table 1. Dynamics of changes in the subjects’ heart rate indices in the initial state and during recovery after exercise in normal conditions, M±m

* – index values that significantly differ from those registered in the initial state (at р£0.05).

The findings indicate certain heterochronism in the dynamics of recovery of different heart rate parameters. Thus, such indicators as AMo and VRI reach their initial level only at the 90th minute of recovery after exercise.

The earlier studies [2, 4] prove that, while the subjects breath oxygen under the conditions of increased pressure (pO₂=0.20 MPa), without pre-exercise, Mo, SDNN and dX of RR intervals duration increase significantly in 5 minutes, and alternatively, heart rate, TI and VRI decrease.

It should be noted that the vector of the above mentioned changes in the heart rate aligns on the whole with that of the changes taking place during the natural recovery after exercise. The unidirectional nature of the heart rate changes, despite their different expressions, may be indicative of an increase in the functional status of athletes from the very beginning of their stay under HBO.

When studying the effect of HBO on the recovery processes after exercise (second series of studies), it was found that the mean values of the studied parameters in the subjects 5 minutes after exercise (Table 2) were almost the same as in the first series, where the regenerative processes took place in normal conditions (see Table 1).

It is to be recalled that oxygen breathing under the conditions of increased pressure began 20 minutes after the end of exercise.

Table 2. Dynamics of the heart rate indices in the subjects in the initial state, 5 minutes after exercise and during further recovery under HBO, М±m

* – index values that significantly differ from those registered in the initial state (at р£0.05);

** – index values that significantly exceed those registered in the initial state (at р£0.05).

The key distinctions of the heart rate recovery after exercise under HBO consisted in the fact that the heart rate indices neared the level of initial values, characterizing the initial state of the body, as early as at the 5^th minute of breathing oxygen under the pressure of 0.20 MPa (which corresponds to the 25th minute of recovery after exercise).

Most indicators reached their initial values 30 minutes after breathing oxygen under the conditions of increased pressure, and the standard deviation of RR intervals and variation range exceeded them significantly.

Further on (during the 50th minute of hyperoxia), the heart rate indices continued to change and go beyond their initial values.

The obtained data may indicate a positive dynamics of the functional status of the subjects and an increase of their physiological reserves.

Conclusions. After exercise under HBO, athletes recover to the initial state, which characterizes their functional status, during the 5th-30th minutes of the training session, i.e. 25-50 minutes after exercise. When recovering in normal conditions, athletes reach their resting indices in 70-90 minutes only.

It is not only accelerated recovery of the body that is typical for HBO, but also expansion of physiological reserves. This is proved by the fact that the majority of the subjects reached the initial indices during the 30th minute of recovery, and later on - even exceeded them.

In general, the obtained data indicate that the regenerative processes that take place in the body after exercise under HBO proceed more efficiently.

References

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