Gavenauskas B. Peculiarities of structural-metabolic adaptation of muscle tissue to combined influence of intermittent hypoxia and prolonged endurance exercise

. Mechanisms of rat muscle tissue adaptation to prolonged endurance training (ET) with load hypoxia development under influence of intermittent hypoxic training (IHT) were a subject of this investigation. It was shown that endurance capacity, maximal oxygen uptake, muscle PO2 (PmO2) maximally increased in those animals who simultaneously underwent ET and IHT. The same animals demonstrated the minimal decrease in PmO2, blood and muscle pH under testing intensive physical workload. The latter led to the lesser shifts of metabolic parameters (lactate and pyruvate concentration, lactate/pyruvate and NAD/NADH ratios) in muscle of rats adapted both to IHT and ET than in rats adapted to ET only. The combined effects of IHT and adaptation to load hypoxia were expressed in an increase of the NADH – oxidation pathway role in the mitochondrial energy production. It was also shown that quantity, linear size, and total surface of muscle mitochondria of different populations have significantly increased as well as capillary density in the skeletal muscle under adaptation both to load hypoxia and intermittent hypoxia. It was found that application of IHT at ET led to a significant increase in superoxidе dismutase and catalase activities in comparison with rats who were not subjected to IHT. Such a rise was responsible for a lack of increasing of muscle lipid peroxidation after testing physical workload.