Withers R T, Ball C T
Exercise Physiology Laboratory, School of Education, Flinders University of South Australia, Bedford Park.
Int J Sports Med. 1988 Feb;9(1):24-8. doi: 10.1055/s-2007-1024973.
The body density (BD), and hence the relative body fat (% BF) was measured for 182 female athletes. The residual volume (RV) was determined both before and after the underwater weighing by a multiple breath helium dilution technique with the subject immersed to neck level. The absolute mean difference (lXdl) and SEE between the two RV trials were 63 and 75 ml, respectively. These increased to values ranging 144-685 and 187-252 ml, respectively, when the mean of the two RV trials for each subject was compared with the RVs predicted via regression equations, estimated from the vital capacity (VC) and assumed to be a constant of 1000 ml. A similar trend resulted from variation of only the RV in the BD formula for each subject. The two RV trials resulted in an lXdl and SEE of .00121 (.5% BF) and .00141 g.cm-3 (.6% BF), respectively, but these increased to values ranging .00283 (1.3% BF) -.01291 (5.7% BF) and .00362 (1.6% BF) -.00527 g.cm-3 (2.5% BF), respectively, for predicted, estimated and assumed constant RVs. In all cases, the lowest lXdl and SEE were associated with the RVs predicted by a multiple regression equation (R = .725; SEE = 187 ml) which was generated on our sample while the largest lXdl values were registered by the other regression equations. These data emphasize that the use of predicted, estimated and constant RVs result in substantial errors in BD and % BF compared with those when the RV is measured.
对182名女性运动员测量了身体密度（BD），进而得出相对体脂率（%BF）。通过多呼吸氦稀释技术，在水下称重前后分别测定残气量（RV），受试者需浸入至颈部水平。两次RV测量的绝对平均差值（lXdl）和标准误（SEE）分别为63毫升和75毫升。当将每个受试者两次RV测量的平均值与通过回归方程预测的RV进行比较时（根据肺活量（VC）估算且假定为常数1000毫升），这些值分别增至144 - 685毫升和187 - 252毫升。每个受试者仅在BD公式中改变RV也产生了类似趋势。两次RV测量得出的lXdl和SEE分别为0.00121（%BF为0.5%）和0.00141克/立方厘米（%BF为0.6%），但对于预测、估算和假定为常数的RV，这些值分别增至0.00283（%BF为1.3%） - 0.01291（%BF为5.7%）和0.00362（%BF为1.6%） - 0.00527克/立方厘米（%BF为2.5%）。在所有情况下，最低的lXdl和SEE与通过多元回归方程预测的RV相关（R = 0.725；SEE = 187毫升），该方程是根据我们的样本生成的，而最大的lXdl值则由其他回归方程记录。这些数据强调，与测量RV时相比，使用预测、估算和恒定的RV会导致BD和%BF出现重大误差。
