Numerous observational studies have examined the physical activity levels and sport training patterns of children and adolescents in relation to bone measures, generally regional and total areal bone mineral density (aBMD). Much of this work has compared children in specific youth sports to non-athlete peers. With exception (12), almost all of the children and adolescents studied have been Caucasian. Almost all these cross-sectional and longitudinal studies report differences in bone measures ranging from 2 to 20% between active and sedentary subjects. Most, but not all, of these studies report no apparent gender interaction. There is some evidence to suggest a physical activity and maturation interaction, but this issue has not been thoroughly studied.

The quantitative measure of bone mass (bone mineral content) provided by the DXA scan is a function of the size of the bone as well as of the amount of mineral within the bone. The amount of true bone mineralization per volume cannot be assessed using DXA. This measurement shortcoming is of particular concern during childhood and adolescence when increases in both area and volume occur, although the timing and tempo for these changes vary among individuals.

Quantitative computed tomography can be used to provide a true measure of volumetric density. By providing a cross-sectional view of the longitudinal axis of bone, it can also be used to sort cortical bone from trabecular bone and therefore provides a means to examine architectural factors influencing bone strength . However, when compared to DXA, the technology exposes subjects to much higher radiation doses. However, peripheral quantitative computed tomography systems are available and used for measuring bones of the wrist and knee in children. Peripheral quantitative computed tomography provides a method to exam regional volumetric and architectural issues with acceptable radiation doses .

12. McKay HA, Petit MA, Khan KM, Schultz RW. Lifestyle determinants of bone mineral: A comparison between prepubertal Asian- and Caucasian-Canadian boys and girls. Calcif Tissue Int 2000;66:320-324.