Zappe D H, Tankersley C G, Meister T G, Kenney W L
Noll Laboratory, Pennsylvania State University, University Park 16802.
Med Sci Sports Exerc. 1993 Nov;25(11):1225-30.
The purpose of this study was to test the hypothesis that changes in exercise intensity dominate the PV response to cycle exercise in the heat independent of the initial plasma volume (PV) and total circulating protein (TCP) content. The two experimental treatments (counterbalanced design) were performed by nine trained male cyclists (age = 23 +/- 1 yr, VO2peak = 63 +/- 4 ml.kg-1.min-1) in both a euhydrated (EU) and hypohydrated (HP, 24-h fluid restriction) state. Blood volume was measured (carbon monoxide dilution) 30 min prior to each test and subsequent changes in PV were calculated from serial venous blood samples using hematocrit and hemoglobin concentration. Following 20 min of seated rest in a warm environment (Tdb = 30 degrees C, 50-60% RH), each subject cycled in a semi-reclining posture for 60 min at three successive intensities (60, 120, and 180 W for 20 min each, representing approximately 22, 37, and 53% VO2peak). Fluid restriction reduced (P < 0.05) body weight by 1.4 +/- 0.3 kg (1.8 +/- 0.4%), PV by 353 +/- 73 ml (8 +/- 2%), TCP by 20 +/- 7 g (7 +/- 2%), and elevated serum osmolality by 6 +/- 2 mOsm.kg-1 (2 +/- 1%). After 20 min of passive heat exposure (prior to exercise), TCP content remained lower (P < 0.05) in HP (17 +/- 5 g) compared with EU as PV increased (P < 0.05) in EU (222 +/- 27 ml) but not (P > 0.05) in HP (122 +/- 35 ml).(ABSTRACT TRUNCATED AT 250 WORDS)
在热环境中，运动强度的变化主导了对骑行运动的血浆容量（PV）反应，而与初始血浆容量和总循环蛋白（TCP）含量无关。九名受过训练的男性自行车运动员（年龄 = 23±1岁，峰值摄氧量 = 63±4 ml·kg⁻¹·min⁻¹）在正常水合状态（EU）和低水合状态（HP，24小时液体限制）下进行了两种实验处理（平衡设计）。在每次测试前30分钟测量血容量（一氧化碳稀释法），并根据连续静脉血样的血细胞比容和血红蛋白浓度计算随后的PV变化。在温暖环境（干球温度 = 30℃，相对湿度50 - 60%）中静坐休息20分钟后，每个受试者以半躺姿势在三个连续强度下骑行60分钟（分别为60、120和180瓦，各持续20分钟，分别约为峰值摄氧量的22%、37%和53%）。液体限制使体重降低（P < 0.05）1.4±0.3 kg（1.8±0.4%），PV降低353±73 ml（8±2%），TCP降低20±7 g（7±2%），血清渗透压升高6±2 mOsm·kg⁻¹（2±1%）。在被动热暴露20分钟后（运动前），与EU相比，HP中的TCP含量仍然较低（P < 0.05）（17±5 g），而EU中的PV增加（P < 0.05）（222±27 ml），但HP中的PV没有增加（P > 0.05）（122±35 ml）。（摘要截断于250字）
