DETERMINANTS OF PARASPINAL MUSCLE CROSS-SECTIONAL AREA IN MALE MONOZYGOTIC TWINS

Background and Purpose. The purpose of this study was to investigate t he general magnitude and relative contributions of anthropometric, lif estyle, and medical history factors and familial aggregation (combined effects of genes and early environment) as determinants of paraspinal muscle cross-sectional area (CSA). Subjects. The subjects were 65 pai rs of male monozygotic twins aged 35 to 65 years ((X) over bar=49, SD= 8). Methods. Study methods included magnetic resonance imaging, percen tage body fat determination, and a detailed interview. Results. Most o f the anthropometric factors were associated with the CSAs. Familial a ggregation was the strongest determinant, however, explaining 66% to 7 3% of the variance in the outcomes beyond what age alone predicted. Le vels of occupational, sport, and leisure-time physical activities repo rted by the subjects had negligible effects. Conclusion and Discussion . The CSAs of the paraspinal muscles were influenced more by some comb ination of genes and early environmental factors than by anthropometri c factors and lifestyle choices in adulthood.