title: The effect of loading and ethnicity on annual changes in cortical bone of the radius and tibia in pre-pubertal children.
abstract: BACKGROUND
  It is unclear what effect habitual physical activity or ethnicity has on annual changes in bone size and strength in pre-pubertal children.
  
  
  OBJECTIVE
  To determine whether the annual relative change in bone size and strength differed between high and low bone loaders and also between black and white pre-pubertal children.
  
  
  METHODS
  Peripheral quantitative computed tomography (pQCT) scans of the 65% radius and tibia were completed on 41 black and white children (15 boys, 26 girls) between the ages of 8-11 years, at baseline and 1 year later. Children were categorised into either a high or low bone loading group from a peak bone strain score obtained from a bone-specific physical activity questionnaire. Total area (ToA), cortical area (CoA), cortical density (CoD), strength-strain index (SSI), periosteal circumference (PC), endosteal circumference (EC) and cortical thickness (CT) were assessed.
  
  
  RESULTS
  There was no difference in annual relative change in radial or tibia bone size and strength between the low and high bone loaders. Black children had a greater annual relative change in CoD (p = 0.03) and SSI (p = 0.05) compared to the white children.
  
  
  CONCLUSIONS
  Children who performed high bone loading activities over a 1-year period had similar bone growth to children who did low bone loading activities over the same period. Rapid maturational growth over this period may have resulted in bone adapting to the strains of habitual physical activity placed on it. Black children may have greater tibial bone strength compared to white children due to a greater annual increase in cortical density.
authors.affiliation: a Exercise Laboratory, School of Physiology, Faculty of Health Sciences , University of the Witwatersrand , Johannesburg , South Africa and.
authors.forename: Rebecca M
authors.initials: RM
authors.lastname: Meiring
authors.affiliation: b MRC/WITS Developmental Pathways for Health Research Unit, Department of Pediatrics, School of Clinical Medicine, Faculty of Health Sciences, University of the Witwatersrand , Johannesburg , South Africa.
authors.forename: Lisa K
authors.initials: LK
authors.lastname: Micklesfield
authors.affiliation: a Exercise Laboratory, School of Physiology, Faculty of Health Sciences , University of the Witwatersrand , Johannesburg , South Africa and.
authors.forename: Joanne A
authors.initials: JA
authors.lastname: McVeigh
mesh_terms: D000886:Anthropometry; D001846:Bone Development / Q000502:physiology; D002648:Child; D000071538:Cortical Bone / Q000000981:diagnostic imaging / Q000502:physiology*; D003710:Demography; D005006:Ethnicity; D005260:Female; D006801:Humans; D008297:Male; D011627:Puberty / Q000502:physiology*; D011884:Radius / Q000000981:diagnostic imaging / Q000502:physiology*; D013977:Tibia / Q000000981:diagnostic imaging / Q000502:physiology*; D014057:Tomography, X-Ray Computed; D016474:Weight-Bearing / Q000502:physiology
keywords: Bone growth; exercise; longitudinal; peripheral QCT