title: A comparison of body composition measurement techniques.
abstract: BACKGROUND
  An understanding of the reproducibility of body composition measurements is essential for effective intervention studies. Air displacement plethysmography (ADP) and bioelectrical impedance (BIA) are two easy-to-use measures of body composition. The present study aimed to assess the reproducibility of ADP and BIA and compare them with each other, as well as with skinfold measurement.
  
  
  METHODS
  Forty-one participants were tested on two occasions following an overnight fast. On test day 1, participants' height, weight and % body fat (BF) were measured using ADP and BIA. Measurements were replicated to assess the within-day reproducibility. On test day 2, participants were again tested using ADP and BIA and had skinfold measurements taken. Three skinfold equations for BF calculation were applied. Comparisons of within- and between-day reproducibility and between measurement techniques were completed using Pearson correlations and Bland-Altman analysis.
  
  
  RESULTS
  Both Pearson correlation and Bland-Altman analysis showed good within- and between-day relationships and agreement for BF from ADP and BIA measurements. The two methods had a high correlation between them; however, the mean difference between the two was 3.1% (4.1%). From the skinfold equations used, the best agreement with ADP had a mean difference of 0.3% (0.8%) and, with BIA, had mean differences of 1.9% (4.2%).
  
  
  CONCLUSIONS
  The data indicate that ADP and BIA cannot be used interchangeably, although both measurements had good within- and between-day agreement.
authors.affiliation: Functional Food Centre, Oxford Brookes University, Oxford, UK.
authors.forename: S E
authors.initials: SE
authors.lastname: Hillier
authors.forename: L
authors.initials: L
authors.lastname: Beck
authors.forename: A
authors.initials: A
authors.lastname: Petropoulou
authors.forename: M E
authors.initials: ME
authors.lastname: Clegg
mesh_terms: D000273:Adipose Tissue; D000328:Adult; D000886:Anthropometry / Q000379:methods*; D001823:Body Composition; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008297:Male; D010991:Plethysmography / Q000379:methods*; D015203:Reproducibility of Results; D012885:Skinfold Thickness; D055815:Young Adult
keywords: air displacement plethysmography; bioelectrical impedance; body fat percentage; reproducibility; skinfold thickness