Secular trends of 22 body dimensions in four racial/cultural groups of American males.

Data from the recent U.S. Army Anthropometric Survey provide a unique opportunity to assess long-term changes in body dimensions within the Army population. This report considers secular trends for 22 body dimensions within four racial/cultural groups: Whites, Blacks, Hispanics, and Asian/Pacific Islanders. Individuals were grouped by year of birth into 5 year cohorts, spanning 1911 to 1970. Rates of secular change were calculated by regressing age-adjusted dimensions against birth year cohort. Results showed that almost all dimensions sustained statistically significant linear trends, the few exceptions occurring in Asian/Pacific Islanders. The greatest rates of change occurred in dimensions related to soft tissues rather than skeletal dimensions. This pattern is consistent with recent American cultural emphasis on health and physical fitness. The causes of the observed trends, insofar as they have been identified, are related to cultural processes. This suggests that biological forces play a diminished role in shaping the patterns of secular change. Therefore, it may be more appropriate to study secular change in groups that are culturally, rather than biologically, defined.