Pathophysiological aspects of the interaction of hypoxia and physical load (experimental study)

Background. A typical extreme factor is hypoxia, which significantly affects the ability to perform tasks of professional activity, in particular, physical activity of various intensity. Physical and neuro-emotional stress under conditions of hypoxia can cause the breakdown of compensatory and adaptive mechanisms with the development of extreme and critical conditions.
The aim of the study. Quantitative assessment of the effect of hypoxia on the physical performance of laboratory animals at different levels of their natural resistance.
Research methods. Modeling of hypoxia was carried out by the methods of pressure chamber rise of laboratory animals and the administration of a methemoglobin former. Resistance to hypoxic hypoxia was assessed by the criterion of the threshold elevation, to hemic hypoxia – by the lifetime. The criterion for the functional state of laboratory animals was their ability to perform physical activity, which was created by treadmill run or swimming with a load.
Results of the study. An altitude of 3500 m causes a decrease in the physical performance of male rats by a third of normoxia level; an altitude of 5000 m – decrease by two times; an altitude of 6500 m – decrease by four times, and at an altitude of 8000 m makes running physical activity by rats impossible. A mild degree of hemic hypoxia causes a decrease in swimming time by almost 2 times, which corresponds to the effect of an altitude of 5000 m on the working capacity; and a moderate degree of hemic hypoxia causes a decrease in swimming time by more than 3 times, which approximately corresponds to the effect of an altitude of 6000 m. The level of resistance to hypoxia has a moderate effect on physical performance, and the factor of a low level of physical performance has almost no effect on the resistance to hypoxia (28 % and 7 % of the trait variability respectively). In animals with an initially low level of resistance to hypoxia, there is also a decrease in working capacity by an average of 20 %.
Conclusion. Hemic hypoxia is an adequate model in studies with a complex effect of various extreme factors. Simulation of mild hypoxia caused by the administration of 30 mg/kg of sodium nitrite is an optimal method.

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