Myhre L G, Hartung G H, Nunneley S A, Tucker D M
J Appl Physiol (1985). 1985 Aug;59(2):559-63. doi: 10.1152/jappl.1985.59.2.559.
Circulatory fluid shifts were studied in middle-aged runners (6 males and 5 females, ages 32-58 yr) during a 42.2-km marathon race run in mild weather (dry-bulb temperature = 17.5-20.4 degrees C). Running times for the subjects were 3:12-4:40 (mean values were 3:34 for males and 4:10 for females). Venous blood samples were taken without stasis in all subjects seated at rest before the start of the race and within 3 min of finishing; eight of the subjects also paused for samples at 6 and 27 km during the race. At 6 km, body weight loss averaged less than 1%, whereas plasma volume (PV) had decreased by 6.5% in male subjects and 8.6% in female subjects. By the end of the race, hypohydration had reached 3.2% in male subjects and 2.9% in female subjects, but PV in both groups remained stable. Sweat rates during the race averaged 545 and 429 g X m-2 X h-1 for male and female subjects, respectively, with ad lib. water intake replacing 21-72% of fluid loss. Increases in plasma protein concentration throughout the race reflected the observed initial decrease in PV. The interpretation of PV responses to exercise and/or hypohydration is critically dependent on selection of base-line conditions; we were able to control for posture-exercise effects by treating the early exercise (6 km) sample as the base line for examining the effects of later fluid loss. Under these conditions, the vascular compartment resisted volume depletion. The ability to maintain stable PV can be explained in part by relationships among oncotic and hydrostatic pressures in the intra- and extravascular fluid compartments.
在温和天气（干球温度 = 17.5 - 20.4摄氏度）下进行42.2公里马拉松比赛期间，对中年跑步者（6名男性和5名女性，年龄32 - 58岁）的循环体液变化进行了研究。受试者的跑步时间为3:12 - 4:40（男性平均值为3:34，女性平均值为4:10）。在比赛开始前所有受试者静息坐位时以及结束后3分钟内，无淤血状态下采集静脉血样；8名受试者在比赛途中6公里和27公里处也暂停采集血样。在6公里处，体重减轻平均不到1%，而男性受试者的血浆量（PV）减少了6.5%，女性受试者减少了8.6%。到比赛结束时，男性受试者的脱水率达到3.2%，女性受试者为2.9%，但两组的PV均保持稳定。比赛期间男性和女性受试者的出汗率平均分别为545和429克×平方米-1×小时-1，随意饮水补充了21 - 72%的液体流失。整个比赛过程中血浆蛋白浓度的增加反映了观察到的PV最初的下降。对PV对运动和/或脱水反应的解释严重依赖于基线条件的选择；我们能够通过将早期运动（6公里）样本作为基线来检查后期液体流失的影响，从而控制姿势 - 运动效应。在这些条件下，血管腔抵抗容量耗竭。维持稳定PV的能力部分可以通过血管内和血管外液腔中胶体渗透压和流体静压之间的关系来解释。
