Thomas T R, Etheridge G L
Can J Appl Sport Sci. 1982 Dec;7(4):258-62.
In order to determine the relationship between reductions in body weight, body volume, and plasma volume, 22 track runners underwent exercises of various intensities and durations. The average mileage performed in the distance runs was 8.4 miles. The average caloric cost was 822 and 288 Cal for the distance and sprint activities, respectively. The overall range of energy expenditure was 100 to 1000 Cal. Before and after the workbout, body volume and density were determined by hydrostatic weighing on each subject. In addition, venous blood samples were analyzed for hematocrit (Hct) and hemoglobin (Hb), and the percent change in plasma volume (% delta PV) was calculated. Body weight and body volume decreases occurred in all subjects. Body density, percent body fat, and plasma volume were significantly altered only in the group of athletes undergoing distance runs. Body weight loss ranged from 0.3 kg to 2.0 kg and was correlated with body volume decreases (r = 0.91) and energy expended (r = 0.73). Body volume changes were related to the extent of density increases (r = 0.58), changes in plasma volume (r = 0.53), and energy enpended (r = 0.75). The % delta PV was significantly related only to changes in body volume. The results of this study indicate that acute exercise does affect body volume and thus the density and % fat determinations. These changes do not parallel closely the changes in plasma volume. The data suggest that for absolute accuracy, the state of hydration of the subject should be controlled prior to hydrostatic weighing. However, even in dehydration caused by prolonged distance running, the density measurement error is small and nearly within the methodological error of the hydrostatic weighing technique.
为了确定体重减轻、身体体积和血浆容量之间的关系，22名田径运动员进行了不同强度和时长的训练。长跑的平均里程数为8.4英里。长跑和短跑活动的平均热量消耗分别为822卡路里和288卡路里。能量消耗的总体范围是100至1000卡路里。在训练前后，通过对每位受试者进行水下称重来测定身体体积和密度。此外，对静脉血样本进行血细胞比容（Hct）和血红蛋白（Hb）分析，并计算血浆容量的百分比变化（%ΔPV）。所有受试者的体重和身体体积均有所下降。仅在进行长跑的运动员组中，身体密度、体脂百分比和血浆容量发生了显著变化。体重减轻范围为0.3千克至2.0千克，且与身体体积的减少（r = 0.91）和能量消耗（r = 0.73）相关。身体体积的变化与密度增加的程度（r = 0.58）、血浆容量的变化（r = 0.53）以及能量消耗（r = 0.75）有关。%ΔPV仅与身体体积的变化显著相关。本研究结果表明，急性运动确实会影响身体体积，进而影响密度和体脂测定。这些变化与血浆容量的变化并非紧密平行。数据表明，为了获得绝对准确的结果，在进行水下称重之前应控制受试者的水合状态。然而，即使是长时间长跑导致的脱水情况，密度测量误差也很小，几乎在水下称重技术的方法误差范围内。
