ADAPTIVE REACTIONS OF THE CARDIOVASCULAR SYSTEM OF GIRLS OF DIFFERENT STAGES OF PUBERTY ON PHYSICAL ACTIVITY DURING THE ACADEMIC YEAR

Controlled physical activity of moderate power working capacity (50% of PWC170) causes a marked change in the cardiovascular system (stroke volume and minute blood volume, heart rate) in 11-16-year-old girls at different stages of puberty (stages 1-5). The reaction of urgent adaptation of girls' cardiovascular system to physical activity during the pubertal period depends on the level of their sexual maturity. The pronounced chronotropic effect of cardiovascular system is revealed in girls at the 1 st and the 2 nd stages of puberty in response to a functional test, during the academic year. The inotropic effect is more pronounced in girls at the 3 rd -5 th stages. There are moderate changes in the studied parameters in response to a functional test and their relatively rapid recovery to the background level in girls at the 1 st and the 2 nd stages of puberty. A long period of wave-like recovery of the studied parameters to the baseline level, with the appearance of "negative phase" of the heart rate recovery, was revealed in girls at the 3 rd and the 4th stages of puberty, at the maximum reactions of stroke volume and minute blood volumes to physical activity. This is regarded as a sign of uneconomic response, unfavorable reaction of the cardiovascular system to the physical activity, the most pronounced at the end of the academic year. The reactions of urgent adaptation of the cardiovascular system to the controlled physical activity during the academic year are characterized by relative stability and economy in girls at the 5 th stage of puberty. There are moderate changes in the heart rate, stroke volume and minute blood volume, and rapid recovery of these parameters to the background level, that indicates good functional capabilities of the cardiovascular system. Keywords: cardiovascular system, stroke volume, minute blood volume, heart rate, puberty stages, pubertal period of ontogenesis, adaptive reactions to physical activity and study load, controlled physical activity