Fig. 1.

For 33% diaphysis (a, c) and 4% metaphysis (b) sites, sample pQCT scans are presented, indicating bone compartments in gymnasts and nongymnasts. For both sites, the “total” compartment includes both cortical and intramedullary/trabecular compartments. Thus, total cross-sectional area (CSA) is the sum of cortical/subcortical and intra-medullary/trabecular CSAs. Total volumetric density (vBMD) is the mean vBMD over the total CSA. For a and b, although randomly selected, the gymnast and nongymnast were well-matched for age and body size (33% SSI and 4% IBS are 69% and 100% greater in the gymnast than the nongymnast, respectively). For c, the scans were specifically selected to illustrate the wide variability in intramedullary cavity characteristics; the gymnast was 5.5 cm taller, but lighter, younger, and less physically mature than the nongymnast (gymnast SSI =271% greater)