Proceedings of the International scientific and practical conference ―New York Global Science Conference 2026‖ (May 18-20, 2026) / Publisher website: www.naukainfo.com. – New York, USA, 2026. - 322 p.

287 erythrocytic indicators may be considered one of the signs of an athlete’s functional prospects. At the same time, adaptive changes in the blood system are not limited to the erythrocytic link. Leukocyte indicators reflect the level of nonspecific defense, body reactivity and the ability to respond to physical stress without developing excessive inflammatory or immunodepressive states. For promising young futsal players, not maximal activation of the leukocyte response is important, but its balance, manifested by the preservation of physiological limits and the absence of signs of functional overstrain. An important result is that cellular resistance indicators make it possible to assess more deeply the stability of the young athlete’s body under repeated training influences. A high or sufficient level of cellular resistance indicates the ability of cells to preserve structural integrity, maintain intracellular homeostasis and counteract endogenous intoxication and oxidative stress. In the selection system, this is of particular importance, since cellular stability determines how well the athlete’s body can tolerate loads without rapid depletion of adaptive reserves. The analysis of integral indices of cellular resistance and endogenous intoxication makes it possible to identify not only the current functional state of a young futsal player, but also hidden signs of adaptive tension. Athletes who maintain a favorable ratio of blood cellular elements, a lower level of intoxication load and the absence of pronounced signs of cellular destabilization may be considered more promising for further specialized training. Indicators of nonspecific resistance are also highly informative for sports selection. They characterize the basic level of natural defense of the body and its ability to resist infectious, inflammatory and stress factors. For young futsal players, it is important not only to demonstrate high motor qualities, but also to maintain a stable immune defense under regular training conditions. An insufficient level of nonspecific resistance may indicate increased vulnerability to overload, frequent illness and disruption of training continuity.