The importance of measuring biological age in longitudinal research of male and female teenagers: Data from the Amsterdam Growth and Health Longitudinal Study (AGAHLS)

Abstract

In the Amsterdam Growth and Health Longitudinal Study (AGAHLS) a group of Dutch teenage boys (n= 148) and girls (n= 159) were monitored during their teens from chronological ages 12 to 18 years. Anthropometric (height, weight and height velocity) and physiological [muscle speed, force and aerobic fitness (V̇ O2max)] characteristics are seemingly more appropriate to classify teenagers according to their biological age. Biological age was estimated (a) by measuring skeletal age from a yearly X-ray photograph of the teenagers’ left hand and wrist, and (b) by calculating the age at Peak Height Velocity (PHV) from height velocity curves. In both boys and girls, mean skeletal age corresponds quite well with their average chronological age. Skeletal age of boys and girls of the same chronological age can differ as much as 5 or 6 years. The steepest slope in height occurs in girls between skeletal ages 11 and 13 and in boys later between 13 and 15 years. Skeletal age and age at PHV can also be important in the description of physiological data such as aerobic fitness (V̇ O2max) and neuromuscular fitness (muscle strength and speed). In relation to skeletal age, the mean V̇ O2max in boys increases at a faster rate between 14 and 16 years than in girls. In relation to age at PHV, the peak in static arm strength and explosive leg strength increases one year after PHV in both boys and girls. This can explain the relative high bone fracture rate during growth spurt. We conclude that biological age can serve as an important parameter to teachers, sports coaches and other health-related professionals for individual enrolment in school physical education, sport clubs (selection and training) and injury prevention.