Wagner D R, Heyward V H, Gibson A L
Exercise and Sports Science Department, Vanguard University of Southern California, Costa Mesa, 92626 USA.
Med Sci Sports Exerc. 2000 Jul;32(7):1339-44. doi: 10.1097/00005768-200007000-00023.
The purpose of this study was to verify the validity of an air displacement plethysmography device (Bod Pod) for estimating body density (Db).
The Db from the Bod Pod (DbBP) was compared with the Db from hydrostatic weighing (DbHW) at residual lung volume in a heterogeneous sample of 30 black men who varied in age (32.0 +/- 7.7 yr), height (180.3 +/- 7.5 cm), body mass (84.2 +/- 15.0 kg), body fatness (16.1 +/- 7.5%), and self-reported physical activity level and socioeconomic status. The Db for each method was converted to relative body fat (%BF) using race-specific conversion formulas and subsequently compared with %BF obtained from dual-energy x-ray absorptiometry (%BFDXA).
Linear regression, using DbHW as the dependent variable and DbBP as the predictor, produced an R2 = 0.84 and SEE = 0.00721 g x cc(-1). However, the mean difference between the two methods (0.00450 +/- 0.00718 g x cc(-1) was significant (P < 0.01). The Bod Pod underestimated the Db of 73% of the sample. The %BF estimates from the Bod Pod, HW, and DXA differed significantly (P < 0.01). The average %BFBP (17.7 +/- 7.4%) was significantly greater than %BFHW (15.8 +/- 7.5%) and %BFDXA (16.1 +/- 7.5%); however, there was no significant difference between %BFHW and %BFDXA.
The Bod Pod significantly and systematically underestimated Db, resulting in an overestimation of %BF. More cross-validation research is needed before recommending the Bod Pod as a reference method.
本研究旨在验证空气置换体积描记法设备（体动仪）用于估算身体密度（Db）的有效性。
在30名年龄（32.0±7.7岁）、身高（180.3±7.5厘米）、体重（84.2±15.0千克）、体脂率（16.1±7.5%）各异且自我报告身体活动水平和社会经济地位不同的黑人男性组成的异质样本中，将体动仪测得的身体密度（DbBP）与余肺容积时的水下称重法测得的身体密度（DbHW）进行比较。使用种族特异性转换公式将每种方法测得的Db转换为相对体脂率（%BF），随后与双能X线吸收法测得的%BF（%BFDXA）进行比较。
以DbHW为因变量、DbBP为预测变量进行线性回归，得出R2 = 0.84，标准误（SEE）= 0.00721克/立方厘米。然而，两种方法之间的平均差异（0.00450±0.00718克/立方厘米）具有显著性（P < 0.01）。体动仪低估了73%样本的Db。体动仪、水下称重法和双能X线吸收法测得的%BF估计值存在显著差异（P < 0.01）。平均%BFBP（17.7±7.4%）显著高于%BFHW（15.8±7.5%）和%BFDXA（16.1±7.5%）；然而，%BFHW和%BFDXA之间无显著差异。
体动仪显著且系统性地低估了Db，导致%BF高估。在推荐体动仪作为参考方法之前，需要更多的交叉验证研究。
