Effect of Clothing Type on Validity of Air-Displacement Plethysmography

The purpose of the study was to evaluate the validity of an air-displacement plethysmography system (AP) within the general population, while wearing (1) a racing-type swimsuit (AP sub(SS)) and (2) participant's personal undergarments (AP sub(UG)), against hydrodensitometry (HW). Fifty women and 50 men were measured for body volume, density, and fat percentage by HW and compared with AP sub(SS) and AP sub(UG). For women, AP sub(UG) and AP sub(SS) were similar, although significant differences (p < 0.001) were observed between AP sub(UG) and HW and between AP sub(SS) and HW. For men, there was no significant difference between AP sub(UG) and HW; however, significant differences (P less than or equal to 0.01) were found between AP sub(UG) and AP sub(SS) and between AP sub(SS) and HW. The small discrepancy in measured values between AP and HW are within the measurement error for the instrumentation and these data support the use of AP for determination of body composition in adults across a wide range of body size (body mass index [BMI] 17.7-35.2 kg times m super(-2)) and age (18-57 y). Participants' personal undergarments provide a practical alternative to a spandex swimsuit when measuring body composition by AP in women but not in men.