| The extended period of growth and development in humans optimizes adaptation and acclimatization to a variety of external factors. Nutrition, disease, and activity mediate the body's response to the environment during growth and can have ramifications for adult health. The influence of the environment is often reflected in the skeleton. In addition to environmental forces, variation in skeletal morphology is determined by genes. To address the extent to which modifications to nutrition and physical activity influence this variation, structural geometry at the proximal femur was analyzed in a sample of adolescent females living in the U.S.;Dual X-ray absorptiometry images of the proximal femora of adolescent females (n = 748) were examined using the Advanced Hip Analysis (AHA) program (GE Lunar). Subjects were recruited from public and private area middle-schools in Arizona, California, Hawaii, Indiana, Nevada, and Ohio. Subjects used in this analysis were female, with age at baseline measurement ranging from 10-12 years. Subjects were self classified as Asian, Hispanic, or White. Females from these ethnic groups were selected because they experience greater bone loss as adults.;Data are presented describing the effect of factors influencing variation in structural geometry. Outcome measures include cross sectional area (A), hip axis length (HAL), distance from center of mass (y), average neck diameter (d3), section modulus (Z), distance form head center to minimum cross sectional moment of inertia (d1), and distance from head center to neck/shaft axis intersection (d2).;Analysis of covariance suggests that lean body mass has a significant effect on each measure of structural geometry. At baseline, there are no significant differences between the experiment and control groups. State of residence and ethnicity were confounded for many of the outcome variables, but ethnic groups differ significantly in these measures of geometry. Tanner stage had a significant effect on A, HAL, and Z. State of residence, a proxy for latitude, had a significant effect on A, HAL, y, and Z in Asians, but not Hispanics. For the most part structural geometry does not appear to be influenced by calcium consumption or physical activity, although there are some exceptions to this. |
