Objective. To form an idea about the fatigue and its role in the process of increasing physical and functional fitness of athletes.
Methods. Analysis and synthesis of scientific literature data; laboratory studies, including the study of 46 indices characterizing changes in work capacity, as well as the severity of tissue hypoxia.
Results. Fatigue is traditionally considered as a negative phenomenon and in this regard, various recommendations aimed at reducing its severity and delaying the onset are proposed. However, in sport, fatigue is widely used to stimulate the adaptation capacities of athletes. According to the author, existing types of muscular activity with various mechanisms of energy supply may suggest the presence of different types of fatigue. Of great importance in the manifestation of fatigue symptoms during strenuous muscular activity is tissue hypoxia that occurs in working muscles. Fatigue (up to a certain limit) is one of the main factors contributing to training effect increase. The author has identified two periods in the process of fatigue development - latent and decompensated. The study of the physiological mechanisms of fatigue development and compensation during strenuous muscular activity, the search for the possibilities of its correction and forecasting are of great practical importance for elite sport. Specific data on changes in the content of blood lactate in athletes associated with an increased rate of oxygen consumption, which contributes to the appearance of both subjective and objective signs of fatigue, are presented. The work also evaluated individual indices characterizing fatigue development in individual world-class athletes.
Conclusion Analysis of the subjective assessment of fatigue shows that among the leading representatives of cyclic sports events, feelings of fatigue become pronounced after 70-75% of the time spent at the ultimate level. The author substantiates the use of high loads of different energy orientation, performed in the face of developed fatigue, as an important factor in increasing work capacity.

На основе комплексного подхода изучены механизмы развития утомления, особенности тканевой гипоксии при напряженной мышечной деятельности.