The adaptation of sportsmen to physical training is accompanied by changes in morphofunctional indicators, the mechanisms of metabolism regulation, and the functioning of the blood circulation. The long-term physical training leads to an increase in the power of mechanisms of the functional respiratory system (FRS). The increase in a load on FRS causes the formation of the hypoxia training, which is revealed on all levels of organism. The study of the mechanisms of adaptation under the indicated hypoxia, which are related to the ultrastructure and the functioning of the mitochondrial apparatus of organism’s cells, is of significant importance, since the damage of mitochondria, which are organelles most sensitive to hypoxia, causes violations in the energy supply, antioxidant protection, and stability of membranes. Myocardium is one of the most active consumers of oxygen in organism. Therefore, the detailed research of its functional state is necessary for the detection of signs of the disadaptation to loads and the prevention of the development of an overstrain and pathological states in sportsmen. Therefore, it is actual to study the peculiarities of changes in the mitochondrial apparatus and the capillarization of myocardium tissues at the modeling of acute and long-term physical training in experiment. The studies are executed on rats-males of the Wistar line 220-250 g in mass. Their physical training was modeled by means of the swimming of rats in a warm water. Under the acute physical training, rats were swimming for 30 min with the additional weight equal to 7.0±3.0 % of body’s mass; the long-term physical training was modeled by a daily 30-min swimming with the analogous additional weight for 3 weeks. The degree of hypoxia was determined by РО2, рН of blood, and the level of consumption of oxygen in percents of VO2max. The determination of the rate of consumption of oxygen was carried out by the manometric method. In morphological and morphometric studies, we used specimens of the heart tops of animals. The preparations for the electron-microscopic studies were produced by the commonly accepted method and studied on an electron microscope, by determining the numbers of functioning capillaries and mitochondria. It is shown that an acute physical training induces the following destructive changes in tissues of rats’ myocardium: edema and destruction of the sarcolemma of cardiomyocytes, destruction of the endothelium of capillaries, and loosening and breaking of the transverse striation of myofibrillae. The negative changes occur also in the ultrastructure of cells: the vacuolization, increase in the number of structurally changed mitochondria, and fragmentation of cristae. This indicates the breaking of the integrity and the dysfunction of the cardiac muscle cells mitochondrial apparatus. The long-term physical training is characterized by structural reconstructions of the adaptive character with reliable increase in the number of functioning capillaries of myocardium tissue (21.2±2.1 unitμm-2 as compared with 14.3±1.2 unitμm-2 under acute training); as well as the increase in the number (15.0±1,3 unitμm-2 as compared with 9.0±0,6 unitμm-2 under acute training) and total area of mitochondria in volume of tissue (14.2±1.0 μm2 as compared with 11.0±0.8 μm2 under acute training). Such changes evidence to an increase in the blood circulation intensity in the microcirculation and the energy power of the mitochondrial apparatus of rats’ myocardium cells, which favor a decrease in manifestations of secondary tissue hypoxia.
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