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.

286 and practically appropriate [4; 5]. Such criteria deepen the understanding of the athlete’s real adaptive potential, allow individualization of the training process, reduce the risk of overload and increase the accuracy of predicting sports prospects. Thus, the study of adaptive mechanisms of the blood system, cellular resistance and immunological reactivity of young futsal players in the context of sports selection is a relevant direction for improving the system of sports reserve training [2; 4; 8]. A comprehensive assessment of these indicators makes it possible to determine not only the level of functional readiness of young athletes, but also their ability for long-term adaptation, stable recovery and further sports development. The aim of the study was to determine the role of blood system indicators, cellular resistance and immunological reactivity in characterizing the adaptive potential of young futsal players and to substantiate the possibility of their use in the system of selection of promising athletes. The conducted analysis showed that the adaptive mechanisms of the blood system, cellular resistance and immunological reactivity are of great importance for assessing the functional readiness of young futsal players and may be considered additional biological criteria for selecting promising athletes. During futsal training, the body of a young athlete is exposed to the complex influence of physical loads of different intensity. This is accompanied by activation of the oxygen-transport function of blood, changes in the leukocyte formula, mobilization of nonspecific defense mechanisms and restructuring of immunological reactivity. These changes reflect not random fluctuations of individual indicators, but an integral adaptive response of the body to systematic training activity. The state of the erythrocytic link of the blood is of particular importance for sports selection, since it ensures oxygen transport to working muscles and determines the level of aerobic support for motor activity. In young futsal players, optimal erythrocyte and hemoglobin values indicate sufficient oxygen-transport potential of the body, which is an important prerequisite for endurance, rapid recovery after load and the ability to maintain a high intensity of game actions. Therefore, the stability of