Introduction

It has long been recognized that physical activity is an important consideration during the growing years if normal growth and development of children are to be maintained (Bar-Or, 1983). Children are generally thought to be naturally physically active. In recent years, however, the physical activity of youngsters has been a subject of great concern to health officials. Up to a generation ago, physical activity was a natural part of life for most children. This is no longer so, and one may well ask whether the child or the adolescent now gets the physical activity required for healthy development. The necessity for physical activity has been greatly reduced, owing to mechanization and automation of work and leisure. Currently, physical activity depends on such factors as body build, physical fitness, and the amount of recreational and sport facilities.

Physical inactivity is an important risk factor for coronary heart disease (CHD). Atherosclerosis starts soon after birth (Montoye, 1985). It is often suggested that a sufficient amount and intensity of regular physical activity could decelerate this process (Powell et al., 1987). However, a prospective epidemiological study, comparing a large number of physically active children with a randomized group of less active children over a long period, has never been conducted and apparently cannot be carried out (Mednick & Baert, 1981). There is unfortunately no possibility of a double-blind study in which physical activity can be measured.