Abstract <p>This review attempts to systematize the few pieces of information available in the literature on the physical capabilities and functional characteristics of senior preschool and primary school children when it is time to start playing sports. It is shown that children of this age are characterized by the predominance of aerobic mechanisms for energy supply of muscular activity, as well as the absence of specialization in motor adaptations in combination with small gender differences in the level of the body’s response to exercise. At the same time, children demonstrate significantly lower performance than adolescents and adults, apparently due to lower efficiency of work, despite the high level of aerobic capacity. Before puberty, the level of anaerobic capacity in children is reduced, which imposes significant restrictions on the loads used in sports.</p>