title: Calibration and validation of an air-displacement plethysmography method for estimating percentage body fat in an elderly population: a comparison among compartmental models.
abstract: BACKGROUND
  The use of hydrostatic weighing (HW) to measure body composition in the elderly can be difficult and is based on the assumption of constancy of body compartments.
  
  
  OBJECTIVE
  We calibrated and validated a new air-displacement plethysmography (AP) method for measuring body composition in the elderly.
  
  
  METHODS
  A 4-compartment equation for calculating percentage body fat (%BF) that used body density (D(b)), total body water, and bone mineral content was used as the criterion for evaluating %BF estimated by the 2- and 3-compartment models. D(b) was measured by HW [D(b(HW))] and by use of the AP instrument [D(b(AP))] in 30 elderly men and 28 elderly women aged 70-79 y.
  
  
  RESULTS
  D(b(AP)) was not significantly different from D(b(HW)). However, analysis of variance showed a significant two-way interaction between sex and compartment model (P < 0.02), indicating that the comparisons between the sexes were different across all compartment models. The %BF calculated for the women was significantly higher than that calculated for the men by both HW and AP and for all compartment models.
  
  
  CONCLUSIONS
  Our data indicate that D(b(AP)) was not significantly different from D(b(HW)). Although differences were seen in %BF between the sexes, we observed no significant differences among the compartment models within each sex for this group of older individuals.
authors.affiliation: Exercise Physiology Laboratory, the Department of Kinesiology, San Francisco State University, CA 94132, USA.
authors.forename: A J
authors.initials: AJ
authors.lastname: Yee
authors.forename: T
authors.initials: T
authors.lastname: Fuerst
authors.forename: L
authors.initials: L
authors.lastname: Salamone
authors.forename: M
authors.initials: M
authors.lastname: Visser
authors.forename: M
authors.initials: M
authors.lastname: Dockrell
authors.forename: M
authors.initials: M
authors.lastname: Van Loan
authors.forename: M
authors.initials: M
authors.lastname: Kern
mesh_terms: D000273:Adipose Tissue; D000368:Aged; D000388:Air; D001823:Body Composition; D001834:Body Water; D001835:Body Weight; D015519:Bone Density; D002138:Calibration; D003720:Densitometry; D005260:Female; D006801:Humans; D006874:Hydrostatic Pressure; D008297:Male; D010991:Plethysmography / Q000379:methods*; D012680:Sensitivity and Specificity