Children are not little adults when it comes to sport!
Knowledge about children and adolescents’ growth and pubertal development is therefore crucial when designing training programmes, assessing the risk of sports injuries and planning preventive measures. Boys and girls have similar growth patterns until puberty starts at 9-14 years of age. Girls‘ puberty starts about 1-2 years before boys’. Girls‘ secondary sexual characteristics begin to manifest around the age of 11 and boys’ around the age of 12. At this time, girls‘ body fat content increases, whereas boys’ growth is predominantly fat-free and primarily occurs in bones and muscles. In Denmark, the average age of first menstruation in girls is 12.5 years and at this time, girls lack an average of 13 cm in height growth.
During the growth period, the body is particularly sensitive to influences such as physical activity and diet. If children and adolescents consume more energy (calories) during the growth period through intensive exercise than is provided by the diet, they enter a negative energy balance, which can result in reduced height growth, among other things.
It is therefore essential that children and young people who play sport consume a diet that contains sufficient energy, vitamins and minerals (including calcium). All of these requirements are fulfilled by a normal good, varied diet. It is therefore a mistake to think that sports activity places special demands on the diet of children and adolescents. Dietary supplements for healthy children and adolescents are therefore never indicated and must be directly discouraged.
Bone mineralisation, density and strength (density) increase during the growth period and only reach their maximum when young people are in their early twenties. After that, the calcium content in the bones decreases steadily throughout life. The higher the calcium content in the bones at age 20, the lower the risk of developing osteoporosis later in life. A regular good, varied diet and regular physical activity increases the calcium content in the bones.
Previous studies on young female gymnasts have shown that intensive physical training can lead to delayed pubertal development, increased incidence of menstrual disorders, delayed bone maturation, decreased bone mineralisation later in life, and low height, weight and body fat percentage relative to age. Lack of menstruation in female athletes multiplies the risk of fatigue fractures. However, other studies have failed to find any adverse effects even after prolonged intensive training during the growth period.
Children and adolescents develop the enzyme systems needed to improve anaerobic capacity (interval training, ‘oxygen training’) only late. These forms of training are therefore meaningless in children. In general, it can be concluded that the physical development of children and adolescents is primarily genetically and hormonally determined and that physical activity and a healthy diet play key roles in this natural development. In the case of growth or menstrual disorders in adolescents, a diet and exercise analysis should be part of the primary medical examination.
