Longitudinal Changes of Aerobic Fitness in Youth Ages 12 to 23.

In the Amsterdam Growth and Health Study, 103 girls and 97 boys were studied five times on a longitudinal basis over a period of 8 years, covering the teenage years from 12 to 17 until young adulthood at 22/23 years. Measured were anthropometric variables such as height, weight (BW), and body fat, and physiological variables such as maximal aerobic power (V̇Omax) and endurance performance (max slope). During the teenage period, V̇Omax/BW remains constant in boys and decreases in girls whereas endurance performance increases in boys and remains constant in girls. By young adulthood V̇Omax/BW and maximal slope have declined in both sexes, and in the case of females are even lower than at the beginning of their teens. Boys superiority in aerobic fitness and the decline in aerobic fitness in both sexes is mainly caused by the differences in the intensity of daily physical activity level.