Garby L, Lammert O, Nielsen E
Department of Physiology, Odense University, Denmark.
Eur J Clin Nutr. 1990 Jul;44(7):545-6.
Several studies have shown that the predictive power of various linear combinations of anthropometric data (body weight, height, sex, age, etc.) to estimate fat free mass is improved after inclusion of measurements of electrical impedance (see eg Khaled et al., 1988). Published algorithms are based on measurements performed under fairly standardized conditions with the subjects at stationary conditions of rest, of environmental temperature and of body fluids. Use of the method under less standardized conditions raises the question of possible effects of deviations from these standard conditions. Hydration and dehydration by 1-2 l of fluid increased or decreased, respectively, the electrical resistance by about 14 per cent and the effects persisted for more than 1 h (Khaled et al., 1988). A change in environmental temperature by 21 degrees C from 35 degrees C to 14 degrees C (with almost constant relative humidity) during 90 min caused an increase in the resistance of about 9 per cent (Caton et al., 1988). The perturbations used in the studies quoted above are fairly drastic and not likely to occur under reasonably controlled field conditions. Therefore, we report here results of measurements of whole body electrical impedance before, during and after a period of 10 degrees C increased environmental temperature and before and after a 5-min period of light to moderate physical exercise.
多项研究表明，在纳入电阻抗测量值后，人体测量数据（体重、身高、性别、年龄等）的各种线性组合对估计去脂体重的预测能力有所提高（见例如Khaled等人，1988年）。已发表的算法是基于在相当标准化的条件下进行的测量，此时受试者处于静止休息状态、环境温度和体液状况稳定。在不太标准化的条件下使用该方法引发了与这些标准条件存在偏差可能产生何种影响的问题。摄入或排出1-2升液体分别会使电阻增加或降低约14%，且这种影响会持续超过1小时（Khaled等人，1988年）。在90分钟内环境温度从35摄氏度变化到14摄氏度（相对湿度几乎恒定）21摄氏度会使电阻增加约9%（Caton等人，1988年）。上述研究中使用的干扰相当剧烈，在合理控制的现场条件下不太可能发生。因此，我们在此报告在环境温度升高10摄氏度期间及之后以及在进行5分钟轻度至中度体育锻炼前后的全身电阻抗测量结果。
