[Effect of hyperoxic inhalations for athletes of different sports, including those who had COVID-19, when training in the middle altitude].

Objective: To identify hyperoxic inhalations on the functional state of the cardiorespiratory system of athletes of different sports, who have previously had COVID-19, when training in the middle altitude.

Material and methods: The study included 64 elite athletes during the preparatory period. The studies were conducted in Kislovodsk in the middle altitude (1240 meters) on the Maloe Sedlo mountain, in the conditions of training camps. We studied the parameters of heart rate variability and functional state of cardiovascular and respiratory systems. Hyperoxic inhalations were performed with the JAY-10 oxygen concentrator (LONGFIAN SCITECH CO., LTD., China). The oxygen concentration in the mixture was 93±3%, capacity - 5 l/min, exposure time - 20 min.

Results: Athletes specializing in sports with predominantly anaerobic lactate and mixed mechanism of energy supply, respectively experiencing hypoxia in the process of their athletic activity during training can experience hypoxia at rest as well. The state of hypoxia during exercise in the middle altitude in such athletes is shown in heart rate variability indices (high values of heart rate and stress index, low power of high frequency waves), low saturation, increased oxygen uptake from the blood microcirculation system. The use of oxygen therapy in athletes promotes positive dynamics of the functional state, consisting in a reduced stress of regulatory mechanisms, strengthened tone of the parasympathetic nervous system in the heart rate regulation, increased economization of the central hemodynamics' parameters, improved functions of the external respiratory system.

Conclusion: Application of hyperoxic inhalations during intense exercise in the middle altitude has a favorable effect on the functional state of the cardiorespiratory system in all the studied sports, especially in athletes who have previously had COVID-19.