Growth of a child can be described as quantifiable changes in body size, shape and composition, or as changes at a functional level in the nervous and the musculoskeletal systems. Parts of the body or different tissues in different sub-systems each have their own growth speed.

This growth is self-evident for everyone who is healthy. Each year a child grows on average about 4–5 cm (with the exception of the baby, toddler, and pre-school growth spurts) and increases on average about 2.5 kg (5.512 lb)in weight.

Each child has his or her own growth speed. Within an age category (e.g. tenth grade at high school or the C-youth with football) there can be a 25 cm height difference or 35 kg (77.16 lb) weight variation between children.

Each child undergoes the same order of growth:

1. the feet, the hands and the head;
2. the arms and the legs;
3. the length of the trunk (back);
4. and the width of the trunk: for boys, the shoulders (Anderson & Twist, 2005; Malina, Bouchard & Bar-Or, 2004a; Malina, Bouchard & Bar-Or, 2013; Viru, Loko, Harro, Volver, et al., 1999).

In the years before the growth spurt, the legs will grow relatively more than the trunk. During the growth spurt, again the legs will start growing earlier than the trunk, but at the end of the growth spurt the size of the different body parts are back in proportion (Cameron, Tanner & Whitehouse, 1982). In daily life, children with ‘too long’ legs in respect to their trunk are often called clumsy. On average, men are 12–14 cm taller than women.

This can be caused, among other factors, because boys grow on average 2 years longer before they reach the growth spurt. In addition, the acceleration of growth is usually bigger for boys than for girls. In the end, multiple factors play a role in the potential final size: genes, nutrition and medical conditions.In many sports we often see a ‘spurt’ after the summer holidays. Although rest and the fact that the children do not have the pressures of schoolwork and homework seem to have an influence on the speed of the growth spurt, it does not affect the final size of an adult.

Some children grow steadily and gradually, whereas for other children the growth curve is more sudden and fierce. The start of the growth spurt is determined not only by genes, but also by environmental factors, such as stress, nutrition and social circumstances, as well as by ethnicity (Malina, Bouchard & Bar-Or, 2004b).Could frequent and hard training of children lead to a disruption in the growth process?

In daily practice it can be noticed that rest can have a positive influence on growth. Top-class gymnasts, for example, grow visibly more during the holidays or a period with less training due to injury. In those cases, a so-called ‘catch-up’ growth can take place. Nevertheless, top-class gymnasts seem to have a delay with respect to the start of the growth spurt (Theodoropoulou, Markou, Vagenakis, Benardot, et al., 2005). The question remains: are these girls smaller because they are gymnasts, or are these girls gymnasts because they are small? The latter seems to be more true (Baxter-Jones & Mundt, 2007

source: athleticskillsmodel.com