title: Effects of daily activities on dual-energy X-ray absorptiometry measurements of body composition in active people.
abstract: OBJECTIVE
  Dual-energy x-ray absorptiometry (DXA) is becoming a popular tool to measure body composition in athletes, owing to its ease of operation and comprehensive analysis of body composition. This study represents the first systematic investigation of the reliability of DXA measurements of body composition in trained individuals and includes measurements of daily variability as well as the specific effect of the intake of a meal.
  
  
  METHODS
  Physically active young adults (15 females, 16 males) underwent five whole-body DXA scans during a 2-d period: in the morning after an overnight fast, ~5 min later after repositioning on the scanning bed, ~8 h later after usual daily activities, and the next morning before and ~30 min after consumption of a simple breakfast. Magnitudes of typical (standard) errors of measurement and changes in the mean of DXA measures were assessed by standardization.
  
  
  RESULTS
  Repositioning produced trivial typical errors for whole-body composition, whereas regional body composition showed substantial errors. Daily activities and consumption of breakfast generally produced a substantial increase in the typical error and mean of DXA estimates of total and regional lean mass and associated body mass.
  
  
  CONCLUSIONS
  Having a standardized scanning protocol and fasted subjects is the most practical way to minimize measurement errors. Future studies involving DXA in measuring body composition should report their scanning and analysis protocol with their associated typical errors of measurement so that the level of reliability can be assessed.
authors.affiliation: AIS Sports Nutrition, Australian Institute of Sport, Canberra, Australian Capital Territory, Australia. louise.burke@ausport.gov.au
authors.forename: Alisa
authors.initials: A
authors.lastname: Nana
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Slater
authors.forename: Will G
authors.initials: WG
authors.lastname: Hopkins
authors.forename: Louise M
authors.initials: LM
authors.lastname: Burke
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods / Q000592:standards*; D000203:Activities of Daily Living; D000328:Adult; D001823:Body Composition; D005260:Female; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D055815:Young Adult