title: Adolescent physical activity and bone strength at the proximal femur in adulthood.
abstract: BACKGROUND
  Physical activity (PA) enhances bone structural strength at the proximal femur in adolescence, but whether these benefits are maintained into early adulthood remains unknown. The purpose of this study was to investigate whether males and females, described as active, average, and inactive during adolescence, display differences in structural strength at the proximal femur in early adulthood (20-30 yr).
  
  
  METHODS
  One hundred four participants (55 males and 49 females) from the Pediatric Bone Mineral Accrual Study (PBMAS) were categorized into adolescent PA groupings (inactive, average, and active) using the Physical Activity Questionnaire for Adolescents. Cross-sectional area and section modulus (Z) at the narrow neck, intertrochanter, and femoral shaft (S) sites of the proximal femur were assessed using hip structural analysis in young adulthood from femoral neck dual-energy x-ray absorptiometry scans. Group differences were assessed using ANCOVA, controlling for adult height (Ht), adult weight (Wt), adolescent bone geometry, sex, percentage adult total body lean tissue (LTM%), and adult PA levels.
  
  
  RESULTS
  Active adolescents had significantly greater adjusted bone geometric measures at all sites than their inactive classified peers during adolescence (P < 0.05). In adulthood, when adjusted for Ht, Wt, adolescent bone geometry, sex, LTM%, and adult PA levels, adolescent participants categorized as active had significantly greater adjusted adult bone geometric measures at the proximal femur than adult participants who were classified as inactive during adolescence (P < 0.05).
  
  
  CONCLUSIONS
  Skeletal advantages associated with adolescence activity appear to confer greater geometric bone structural strength at the proximal femur in young adulthood.
authors.affiliation: 1College of Kinesiology, University of Saskatchewan, Saskatoon, SK, CANADA; 2Department of Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, SK, CANADA; and 3Department of Medical Imaging, John Hopkins University Baltimore, MD.
authors.forename: Stefan A
authors.initials: SA
authors.lastname: Jackowski
authors.forename: Saija A
authors.initials: SA
authors.lastname: Kontulainen
authors.forename: David M L
authors.initials: DM
authors.lastname: Cooper
authors.forename: Joel L
authors.initials: JL
authors.lastname: Lanovaz
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Beck
authors.forename: Adam D G
authors.initials: AD
authors.lastname: Baxter-Jones
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000886:Anthropometry; D001823:Body Composition; D015519:Bone Density; D002648:Child; D005260:Female; D005269:Femur / Q000502:physiology*; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult