Abstract des Autors

The growth curves for height and weight in Flemish boys and girls in the current population do not differ from other populations. No sexual differences are noted between the ages of 6 and 10. After the well-known 'crossing-over' period, boys are taller and heavier than girls. Girls have more subcutaneous fat than boys at all ages and the differences become greater with increasing age. For the health-related fitness components, the sex differences are rather small between 6 and 12 years of age. From the onset of the adolescent growth spurt for boys, the sex differences become especially apparent with girls showing generally no more improvement of their fitness while in boys it still increases. In contrast with cardiorespiratory endurance and the muscular endurance tests, girls perform better than boys for flexibility. For performance-related fitness tests such as static strength, explosive strength and running speed, boys obtained better results than girls at all ages. The growth curves were parallel between 6 and 12 years of age. From that age onwards, the differences become greater. For the flamingo balance test and for plate tapping, no substantial sex differences were noted. Sexual dimorphism in motor fitness components can be explained by a large number of factors, such as differences in physiological, biochemical and endocrinological characteristics which undoubtedly influence physical fitness. Body size and body composition are important factors that affect performance in a number of health-related and motor fitness tests. Body size and subcutaneous fatness have no or little effect on flexibility, speed of limb movement and balance, but for cardiorespiratory endurance, the different strength tests and for running speed, they play a significant role in the explanation of the observed sex differences. However, when sex differences are controlled for subcutaneous fatness, weight and height, boys perform still significantly better during adolescence in all strength tests as well as regarding cardiorespiratory endurance. Therefore, other factors such as social and motivational variables, sex differences in physical activity and role patterns may contribute to the explanation of sex differences in physical fitness. Verf.-Referat