"Interest in the effects that physical activity and/or exercise have on a childs growth and maturation has a long history. At the beginning of the 20th century DArcy Thompson1 wrote his classic treatise On Growth and Form suggesting that exercise was a direct stimulus to growth. In 1964, James Tanner2 published The Physique of the Olympic Athlete in which he concluded that the basic body structure must be present for the possibility of being an athlete to arise. Other authors who have subsequently measured the growth and development of young athletes have agreed with this statement and concluded that body size is likely genotypic and probably reflects selection at a relatively young age for the size demands of the sport.3 However, a number of studies, especially with aesthetic sports such as gymnastics, have suggested that when heavy training regimens are started at a young age the growth and maturation of the child may be adversely affected.4 (Interested readers are referred to Chapter 30 for discussion of the morphology of youth athletes)"--