Abstract
The article analyzes the results of a study of maximum oxygen consumption (VO2max) as an integral indicator of the effectiveness of the training process in athletes of the Republic of Kazakhstan national cross-country skiing team during three annual macrocycles. An in-depth comprehensive examination in laboratory conditions revealed an insufficient level of development of the respiratory system (VC, FI, MVL), maximum physical performance, as well as aerobic and anaerobic capabilities of athletes. Based on the data obtained, it was assumed that the reason for such results is insufficient attention to basic training and low-power aerobic training in the structure of the annual macrocycle. It was found that with long-term aerobic work, the function of the respiratory system develops, the vital capacity of the lungs (VC), the alveolar surface and the capillary network, as well as the endurance of the respiratory muscles increase. Aerobic training leads to an increase in the size and number of mitochondria, which plays a key role in maintaining oxygen homeostasis at the cellular and systemic levels.