There were studied morphofunctional peculiarities of biological development of 15– 17 year old boys’ organisms on the bases of complex use, for this, of the level of physical development, retes of sex maturity and somatotype. On that base there were studied the individual peculiarities of their adaptation to the physical loads, which was directed to the development of endurance. It was ascertained, that the boys of the examined age groups, based on the complex differentiation are divided into 3 basic groups — fast, normal and slow rates of genesis. These typological groups differ by the measure and quantity of periods of long-term adaptation, and by the nature of adaptable changes in the organisms which are studied as a result of influence of long- lasted dosing loads, directed to the development of endurance.