title: Effect of level of farm mechanization early in life on bone later in life.
abstract: OBJECTIVE
  To determine whether an active rural lifestyle during childhood and adolescence, defined as low farm mechanization, was associated with bone measures later in life.
  
  
  METHODS
  DXA bone data from total body, hip and spine, and pQCT data from 4% and 20% distal radius were obtained on 330 individuals (157 women) aged 20-66 years who farmed at least 75% of their lives. Primary bone outcomes included areal bone mineral density (aBMD), aBMD Z-scores, cortical and trabecular volumetric BMD, cortical thickness and periosteal circumference. Relationship between bone and recall of level of farm mechanization as a child was determined after stratifying by sex and controlling for covariates.
  
  
  RESULTS
  Controlling for covariates, females from low mechanized farms had higher femoral neck (FN) bone area (p=0.03) than those on high or moderate mechanized farms. No group differences in pQCT ulna measurements or z-scores were found in either gender.
  
  
  CONCLUSIONS
  A low farm mechanization level (high physical activity) prior to 20 years of age is associated with greater FN bone area in females. Future research that includes type and amount of physical activity performed will contribute to growing knowledge of how and when regular physical activity during childhood and adolescence affects adult bone health.
authors.affiliation: E.A. Martin Program in Human Nutrition, South Dakota State University, Brookings, South Dakota 57006, United States.
authors.forename: L A
authors.initials: LA
authors.lastname: McCormack
authors.forename: T L
authors.initials: TL
authors.lastname: Binkley
authors.forename: B L
authors.initials: BL
authors.lastname: Specker
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D000328:Adult; D000368:Aged; D000383:Agriculture / Q000379:methods*; D015519:Bone Density; D001846:Bone Development / Q000502:physiology*; D001842:Bone and Bones / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008019:Life Style; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D012424:Rural Population; D014057:Tomography, X-Ray Computed; D055815:Young Adult