Gore C J, Scroop G C, Marker J D, Catcheside P G
Department of Physiology, University of Adelaide, South Australia.
Eur J Appl Physiol Occup Physiol. 1992;65(4):302-10. doi: 10.1007/BF00868132.
While haemoconcentration due to loss of plasma volume is well established during cycling, the existence of similar changes during running remains contentious. This study compared the changes in plasma volume and associated blood indices during 60 min of running and cycling at the same relative intensity (approximately 65% VO2max), with all changes referenced to blood indices obtained after 30 min seated at rest on a cycle ergometer. Plasma osmolarity increased similarly with both forms of exercise but was less than predicted for water loss alone, such that there was a net loss of sodium during exercise and of potassium postexercise, with essentially no loss of protein. Plasma volume decreased similarly (approximately 6.5%) in both exercise trials, but while that with cycling was initiated by exercise itself and was essentially maximal within 5 min, the reduction in plasma volume in the running trial was induced by adopting the upright posture and was complete before exercise began. These data would indicate that different mechanisms are responsible for the changes in plasma volume induced by running and cycling, while the similarity of change would suggest that there is a lower limit to any reduction in plasma volume, regardless of mechanism. Furthermore, the observation that the changes in plasma volume were complete before or early in exercise, would imply that oral water ingestion during prolonged exercise, which is essential for thermoregulation, may be more concerned with homeostasis of extravascular water rather than plasma volume.
虽然在骑行过程中因血浆量减少导致血液浓缩已得到充分证实，但跑步过程中是否存在类似变化仍存在争议。本研究比较了在相同相对强度（约65%最大摄氧量）下跑步和骑行60分钟期间血浆量及相关血液指标的变化，并将所有变化与在自行车测力计上静息坐姿30分钟后获得的血液指标进行对比。两种运动形式下血浆渗透压的升高情况相似，但低于仅因水分流失所预测的数值，以至于运动期间钠有净流失，运动后钾有流失，而蛋白质基本没有流失。在两项运动试验中，血浆量的减少情况相似（约6.5%），但骑行时血浆量的减少是由运动本身引发的，且在5分钟内基本达到最大值，而跑步试验中血浆量的减少是由于采取直立姿势所致，且在运动开始前就已完成。这些数据表明，跑步和骑行引起的血浆量变化是由不同机制导致的，而变化的相似性则表明，无论机制如何，血浆量减少存在一个下限。此外，血浆量变化在运动前或运动早期就已完成这一观察结果意味着，长时间运动期间的口服补水对于体温调节至关重要，可能更多地与血管外水分的稳态而非血浆量有关。
