title: Determinants of paraspinal muscle cross-sectional area in male monozygotic twins.
abstract: OBJECTIVE
  The purpose of this study was to investigate the general magnitude and relative contributions of anthropometric, lifestyle, and medical history factors and familial aggregation (combined effects of genes and early environment) as determinants of paraspinal muscle cross-sectional area (CSA).
  
  
  METHODS
  The subjects were 65 pair of male monozygotic twins aged 35 to 65 years (mean = 49, SD = 8).
  
  
  METHODS
  Study methods included magnetic resonance imaging, percentage body fat determination, and a detailed interview.
  
  
  RESULTS
  Most of the anthropometric factors were associated with the CSAs. Familial aggregation was the strongest determinant, however, explaining 66% to 73% of the variance in the outcomes beyond what age alone predicted. Levels of occupational, sport, and leisure-time physical activities reported by the subjects had negligible effects.
  
  
  CONCLUSIONS
  The CSAs of the paraspinal muscles were influenced more by some combination of genes and early environmental factors than by anthropometric factors and lifestyle choices in adulthood.
authors.affiliation: Department of Environmental Health, University of Washington, Seattle 98195, USA.
authors.forename: L E
authors.initials: LE
authors.lastname: Gibbons
authors.forename: T
authors.initials: T
authors.lastname: Videman
authors.forename: M C
authors.initials: MC
authors.lastname: Battié
authors.forename: J
authors.initials: J
authors.lastname: Kaprio
mesh_terms: D000273:Adipose Tissue; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D000886:Anthropometry; D001416:Back Pain / Q000209:etiology; D001823:Body Composition; D015444:Exercise; D006801:Humans; D008019:Life Style; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000033:anatomy & histology*; D019547:Neck Pain / Q000209:etiology; D012044:Regression Analysis; D013131:Spine; D014430:Twins, Monozygotic / Q000235:genetics*