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.

284 It is substantiated that the assessment of blood system indicators makes it possible to determine the level of oxygen-transport support of the body, the degree of functional readiness and the athlete’s ability to tolerate training loads without developing overstrain. A high level of cellular resistance characterizes the body’s ability to counteract endogenous intoxication, oxidative stress and microdamage that occur during intensive muscular activity. Indicators of immunological reactivity reflect the state of nonspecific and specific immune defense, as well as the adaptive capacity of the body under regular physical loads. It is proved that the comprehensive use of hematological, cellular-resistance and immunological indicators in the system of sports selection increases the objectivity of assessing the functional potential of young athletes, allows timely detection of signs of adaptive tension and optimizes the organization of the training process. It has been established that the combination of high functional stability, effective immune adaptation and stability of the blood system is an important prerequisite for long-term sports improvement in futsal. Keywords: futsal, young futsal players, sports selection, blood system, cellular resistance, immunological reactivity, adaptation, physical loads, nonspecific resistance, functional readiness, adaptive potential. The selection of promising young futsal players is one of the key tasks of the modern system of sports reserve training. The effectiveness of this process depends not only on the assessment of technical and tactical skills, physical fitness and game thinking, but also on a comprehensive analysis of the athlete’s functional state [2; 3]. Of particular importance is the identification of biological markers that reflect the ability of the young body to adapt to systematic physical loads, maintain the stability of the internal environment and preserve a high level of working capacity under training and competitive conditions [8; 10]. Futsal, as a team sport, is characterized by a high density of motor actions, frequent accelerations, stops, changes of direction, physical duels and short recovery periods. Such activity places increased demands on the functional reserves of the