Millard-Stafford M L, Collins M A, Evans E M, Snow T K, Cureton K J, Rosskopf L B
Exercise Research Laboratory, Department of Health and Performance Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA.
Med Sci Sports Exerc. 2001 Aug;33(8):1311-7. doi: 10.1097/00005768-200108000-00011.
To compare measurements of body density (D(b)) obtained from air displacement plethysmography (AP) and hydrostatic weighing (HW) and to determine the accuracy of substituting D(b) via AP (D(b)-AP) for D(b) via HW (D(b)-HW) in estimating body fatness (%Fat(4C)) and the composition and density of the fat-free mass (Dffm) from a four-component model (fat, mineral, water, and protein).
D(b) was measured in 50 young adults using AP and HW. Total body water via deuterium dilution, bone mineral content via dual-energy x-ray absorptiometry, and D(b) were used to estimate %Fat(4C).
D(b)-AP and D(b)-HW were highly correlated (r = 0.89, SEE = 0.008 g x mL(-1)), but D(b)-AP (1.065 +/- 0.003 g x mL(-1)) was significantly higher (P < 0.05) than D(b)-HW (1.058 +/- 0.003 g x mL(-1)), resulting in a mean difference of 2.8%fat. Differences between %Fat(4C-AP) (17.8 +/- 1.2%) and %Fat(4C-HW) (19.3 +/- 1.2%) were significant (P < 0.05), but the SD of the differences (2.3%) was low. When D(b)-AP was used in a four-component model in place of D(b)-HW, the calculated Dffm was significantly higher (1.109 +/- 0.002 vs 1.105 +/- 0.002 g x mL(-1)) based on a higher (P < 0.05) protein fraction (22.0 +/- 0.4% vs 20.6 +/- 0.4%) and lower (P < 0.05) water (71.1 +/- 0.4% vs 72.4 +/- 0.4%) and mineral fractions (7.0 +/- 0.1% vs 7.1 +/- 0.1%).
AP yields a higher D(b) than HW and may not be a valid method for measuring D(b) or estimating %fat using densitometry. However, due to relatively small bias and low individual error, D(b)-AP is an acceptable substitute for D(b)-HW when estimating %fat with a four-component model in young adults.
比较通过空气置换体积描记法（AP）和水下称重法（HW）获得的身体密度（D(b)）测量值，并确定在根据四成分模型（脂肪、矿物质、水和蛋白质）估计体脂率（%Fat(4C)）以及无脂肪质量的组成和密度（Dffm）时，用AP法测得的D(b)（D(b)-AP）替代HW法测得的D(b)（D(b)-HW）的准确性。
使用AP和HW对50名年轻成年人进行D(b)测量。通过氘稀释法测量总体水，通过双能X线吸收法测量骨矿物质含量，并使用D(b)来估计%Fat(4C)。
D(b)-AP与D(b)-HW高度相关（r = 0.89，标准误 = 0.008 g·mL(-1)），但D(b)-AP（1.065±0.003 g·mL(-1)）显著高于（P < 0.05）D(b)-HW（1.058±0.003 g·mL(-1)），导致平均体脂差异为2.8%。%Fat(4C-AP)（17.8±1.2%）与%Fat(4C-HW)（19.3±1.2%）之间的差异具有统计学意义（P < 0.05），但差异的标准差（2.3%）较低。当在四成分模型中使用D(b)-AP代替D(b)-HW时，基于较高的（P < 0.05）蛋白质比例（22.0±0.4%对20.6±0.4%）、较低的（P < 0.05）水比例（71.1±0.4%对72.4±0.4%）和矿物质比例（7.0±0.1%对7.1±0.1%），计算得到的Dffm显著更高（1.109±0.002对1.105±0.002 g·mL(-1)）。
AP法得出的D(b)高于HW法，可能不是测量D(b)或使用密度测定法估计体脂率的有效方法。然而，由于偏差相对较小且个体误差较低，在年轻成年人中使用四成分模型估计体脂率时，D(b)-AP可作为D(b)-HW的可接受替代方法。
