The relationship between blood volume, blood properties and work capacity.

提高运动能力或最大摄氧量的机制已从心血管能力或携氧能力的角度得到广泛研究，但血容量扩张是否具有提高最大摄氧量的潜力仍存在争议，本实验测定了具有广泛运动能力的受试者的最大摄氧量，同时测定了循环血容量和血浆容量。通过测定空气中运动和水中运动时的右心房压力和心钠素（ANP），以及循环血浆容量的变化，分析了运动时血浆容量下降的机理及其与运动能力的关系，结果发现，血容量和血浆容量与最大摄氧量之间存在高度显著的相关性。此外，我们的研究结果表明，最大摄氧量的增加与血浆容量的增加比与血容量的增加更相关，在最大摄氧量的60%的运动期间，循环血浆容量平均下降约4%，血浆心钠素与右房压和心率乘积呈高度相关提示心脏收缩时心房压力是心钠素分泌的刺激因素。在大鼠体外循环中连续测定循环血容量和血液性质的实验也得到了类似的结果，综合这些结果，认为血浆容量的增加有利于维持心输出量，有利于运动时体温的调节。还表明，随着运动训练，血浆容量增加和心率降低有助于维持运动能力。

The mechanism to increase exercise performance or maximal oxygen uptake has been widely studied from the point view of cardiovascular performance or oxygen carrying capacity, while controversy exists as to whether blood volume expansion has the potential to increase maximal oxygen uptake.In this experiment, maximal oxygen uptake was determined on subjexts with wide range of exercise ability, simultaneously with circulating blood volume and plasma volume. The right atrial pressure and ANP during exercise in air and also with water immersion were determined together with the changes in circulating plasma volume, and the mechanism of plasma volume decrease during exercise was analyzed in the relationship with the ability to exercise.As the results, we found highly significant correlation between blood and plasma volumes and maximal oxygen uptake. In addition, our results indicated that the increase of maximal oxygen uptake is more related with the increase of plasma volume than that of blood volume.During exercise at 60% of maximal oxygen uptake, circulating plasma volume showed decrease by about 4% on an average, and the decrease showed correlation with the increases in plasma ANP.Plasma ANP showed high correlation with the product of right atrial pressure and heart rate than with right atrial pressure alone, which suggests that stimuli for ANP secretion is right atrial pressure during heart contraction. Similar results were obtained from the experiment on rats in which circulating blood volume and blood properties were measured continuously on by-passed extra-corporeal circulation.Summarizing these results, it is suggested that the plasma volume expansion is favorable for the maintenance of cardiac output, and regulation of body temperature during exercise. It is also suggested that the increase in plasma volume and the decrease in heart rate with exercise training contribute to maintain exercise performance.