Effect of 5-versus 3-lessons-a-week physical education program upon the physical development of 12 and 13 year old schoolboys.

The importance of physical exercise in relation to the development of children in its widest sense has generally been accepted. ' ' 2 * On one hand physical activity among young people in Western European countries continually decreases : amongst other reasons this hypokinesia is caused by the continually decreasing availability of play and recreation-grounds in and near the large cities. On the other hand the abundant up take of foodstuffs with a high fat percentage does exceed the daily caloric intake above caloric output. This is the reason why it appears to be essential to raise the level of physical activity of the pupils by increasing the number of weekly lessons in physical education. At most schools in the Netherlands the number of lessons varies from 2 to 3 lessons a week. In the various curricula for physical education one finds the aims of physical education described as follows : "The object of physical education is (a) to promote a favourable influence on the development of the body, (b) to promote