Saunders M J, Blevins J E, Broeder C E
Department of Physical Education, Exercise and Sport Sciences, East Tennessee State University, Johnson City 37614, USA.
Med Sci Sports Exerc. 1998 Jun;30(6):885-92. doi: 10.1097/00005768-199806000-00017.
The purpose of this study was to determine how differences in hydration states and ion content of hydrating fluids affected bioelectrical impedance (BI) and hydrostatic weighing (HW) measurements.
Fifteen athletic subjects aged 19-56 yr were recruited. Relative body fat (%), fat-weight (FW), and fat-free weight (FFW) were assessed using BI and HW under normal conditions (N), hypohydration (HPO), rehydration (RHY), and superhydration (SHY) states. During the RHY and SHY trial periods, subjects were hydrated with either distilled water or an electrolyte solution (ELS). HPO and SHY levels were set at 3% of each person's normally hydrated body weight.
Comparison between the distilled water and the ELS trials indicated that hydration solution had no effect on BI or HW. Thus, the results presented are the trial means of both hydration solutions combined. Both BI and HW were shown to be highly test-retest reliable (r-values: 0.96 and 0.99, respectively). The effects of exercise induced HPO followed by RHY on body composition values indicated that HW was very stable across measurement periods while BI was not. From N to the HPO state, BI %BF declined from 14.4 +/- 5.3% to 12.3 +/- 5.3%, respectively. After RHY, BIA %BF increased to 15.5 +/- 5.8%. Similar findings occurred when subjects were superhydrated (N-BI = 13.2 +/- 5.3%; SHY-BI = 15.4 +/- 5.6%). With a comparison of the intercepts and slopes of HW and BIA for the N and SHY states, it was clear hydration status significantly affected the intercepts (HW: 0.37 vs. BI: 1.85) and not the slopes (HW: 1.00 vs BI: 0.99). As a result, a majority of all fluid changes were interpreted as FW by BI. During HPO, 82% of the weight loss was considered FW while during RHY or SHY, 128% and 85% of the water weight regain/gain was considered FW.
These results indicate that BI is not a valid technique in athletes, especially when wanting to determine body composition effects of training/detraining. This study indicates that even small fluid changes such as those that occur with endurance training may be interpreted incorrectly as changes in an athlete's body fat content.
本研究的目的是确定补水状态及补水液离子含量的差异如何影响生物电阻抗（BI）和水下称重（HW）测量结果。
招募了15名年龄在19 - 56岁的运动员受试者。在正常状态（N）、低水合状态（HPO）、再水合状态（RHY）和高水合状态（SHY）下，使用BI和HW评估相对体脂（%）、脂肪重量（FW）和去脂体重（FFW）。在RHY和SHY试验期间，受试者用蒸馏水或电解质溶液（ELS）进行补水。HPO和SHY水平设定为每个人正常水合体重的3%。
蒸馏水试验和ELS试验的比较表明，补水溶液对BI或HW没有影响。因此，给出的结果是两种补水溶液合并后的试验均值。BI和HW都显示出高度的重测可靠性（r值分别为0.96和0.99）。运动诱导的HPO随后是RHY对身体成分值的影响表明，HW在各测量期间非常稳定，而BI则不然。从N状态到HPO状态，BI %BF分别从14.4±5.3%降至12.3±5.3%。RHY后，BIA %BF增加到15.5±5.8%。当受试者处于高水合状态时也出现了类似的结果（N - BI = 13.2±5.3%；SHY - BI = 15.4±5.6%）。通过比较N和SHY状态下HW和BIA的截距和斜率，很明显水合状态显著影响截距（HW：0.37对BI：1.85）而不影响斜率（HW：1.00对BI：0.99）。因此，BI将所有液体变化的大部分解释为FW。在HPO期间，82%的体重减轻被认为是FW，而在RHY或SHY期间，128%和85%的体重恢复/增加被认为是FW。
这些结果表明，BI在运动员中不是一种有效的技术，尤其是在想要确定训练/停训对身体成分的影响时。本研究表明，即使是像耐力训练中出现的微小液体变化，也可能被错误地解释为运动员体脂含量的变化。
