[Anatomic, physiological and metabolic characteristics of young athletes]

A rational approach to the organization of the training process, the competitive cycle, the recovery processes in the practice of child and youth sport requires knowledge of the anatomical and physiological characteristics of the organism in these age periods. Exchange of amino acids in children of 6 to 12 years takes place very actively providing processes of growth and development. The children of preschool and early school age have tendency to hypoglycemia due to the imperfection of neurohumoral regulation of the mobilization of glycogen in the liver and increased utilization of glucose. Glucose utilization corresponds to its level in adults, ranging from 8 to 14 years of age. In children under the age of 10 an increased tendency to the formation of ketone bodies and ketosis is determined. Cholesterol levels increase rapidly after birth. From the period of puberty, girls have higher levels of total cholesterol, cholesterol in low density lipoprotein (LDL) and high density lipoproteins (HDL) than boys. At the age of 6-12 years basal metabolic rate decreases to 1.3-1.5 kcal/kg/h. The muscular system increasingly develops. Functional features of the central nervous system is the predominance of excitation. Sympathetic part of the autonomic nervous system prevails in heart's activity. The role of the hypothalamic-pituitary system significantly increases in the structure of the endocrine glands. The sensitivity of many endocrine glands to the tropic hormone produced in the adenohypophysis increases. At the age of 8-12 years the role of epinephrine, norepinephrine and other biogenic amines especially increases. Period of puberty at the age of 13-17 years is associated with a significant change in the hormonal status of the organism. A pubertal growth spurt takes place, which occurs 1-2 years earlier in girls than in boys. As for the skeletal system the most pronounced growth of tubular bones of the limbs, spine and increase of bone density, muscle mass occurs. Heart rate decreases, while the duration of the expulsion phase of blood, cardiac output, respiratory functional parameters and red blood cells and hemoglobin concentrations increase. Endurance rises, physical activity is more economical than in childhood.