SEASONAL DYNAMICS OF ENDOCRINE REGULATION OF METABOLIC RATE, BLOOD OXYGEN TRANSPORT SYSTEM AND PHYSICAL PERFORMANCE OF MIDDLE OB REGION ATHLETES FROM CYCLIC WINTER SPORTS

Aim. The paper aims to study the seasonal dynamics of endocrine regulation of metabolic rate, blood oxygen transport system and physical performance of Middle Ob region athletes from cyclic winter sports. Materials and methods. A comprehensive two-stage study of the endocrine system, blood oxygen transport system and physical performance was carried out among elite cross country skiers and biathletes aged from 15 to 18 years during the periods of the year with pronounced daylight variability. The research methods included enzyme-linked immunoassay (ELISA) with the measurements of total triiodothyronine, total thyroxine, thyroid-stimulating hormone, total testosterone and growth hormone; analysis of peripheral blood with the measurements of red blood cells, hemoglobin, hematocrit and red blood cell indices; cardiopulmonary exercise testing with ergospirometry and assessment of maximum oxygen consumption, physical work capacity, oxygen pulse and anaerobic threshold. Results. Statistical analysis revealed significant (p < 0.05) seasonal changes in the endocrine system, blood oxygen transport system and physical performance of Middle Ob region athletes. Namely, during the short daylight period there was a significant increase in total triiodothyronine and cortisol, a decrease in total testosterone, red blood cells, hemoglobin, hematocrit and the average volume of red blood cells, an increase in absolute and relative values of maximum oxygen consumption, oxygen pulse, physical work capacity and a decrease in anaerobic threshold. Conclusion. The results of the research characterize the features of athletes’ adaptation to specific climatic factors of the Northern region against the background of intense physical exertion.