title: Physical activity augments bone mineral accrual in young children: The Iowa Bone Development study.
abstract: OBJECTIVE
  This 3-year follow-up study examined associations between physical activity and bone mineral content (BMC) and whether physical activity augments BMC accrual.
  
  
  METHODS
  Participants were 370 children (mean age baseline 5.3 years, follow-up 8.6 years). Physical activity was measured using 4-day accelerometry. BMC was measured using dual energy x-ray absorptiometry.
  
  
  RESULTS
  After adjustment for baseline BMC, age, and body size, mean physical activity predicted follow-up BMC at the hip, trochanter, spine, and whole body in boys and at the trochanter and whole body in girls. The variability in BMC explained by physical activity was modest (1% to 2%). However, based on a general linear model with adjustment for baseline BMC and body size, children who maintained high levels of physical activity accrued, on average, 14% more trochanteric BMC and 5% more whole-body BMC relative to peers maintaining low levels of physical activity.
  
  
  CONCLUSIONS
  This study suggests that maintaining high levels of everyday physical activity contributes to increases in BMC in young children, particularly at the trochanter.
authors.affiliation: Department of Health and Sport Studies, The University of Iowa, Iowa City, Iowa 52242, USA. kathleen-janz@uiowa.edu
authors.forename: Kathleen F
authors.initials: KF
authors.lastname: Janz
authors.forename: Julie M
authors.initials: JM
authors.lastname: Gilmore
authors.forename: Trudy L
authors.initials: TL
authors.lastname: Burns
authors.forename: Steven M
authors.initials: SM
authors.lastname: Levy
authors.forename: James C
authors.initials: JC
authors.lastname: Torner
authors.forename: Marcia C
authors.initials: MC
authors.lastname: Willing
authors.forename: Teresa A
authors.initials: TA
authors.lastname: Marshall
mesh_terms: D015519:Bone Density / Q000502:physiology*; D001846:Bone Development / Q000502:physiology; D002648:Child; D002675:Child, Preschool; D005260:Female; D005269:Femur / Q000502:physiology; D005500:Follow-Up Studies; D006801:Humans; D007484:Iowa; D016018:Least-Squares Analysis; D008019:Life Style; D016014:Linear Models; D008297:Male; D009043:Motor Activity / Q000502:physiology*