Abstract des Autors

During acute aerobic exercise the venoconstriction, mainly occurring in the splanchnic circulation, increases venous return. Total blood volume decreases because of fluid shift from intra- to extravascular compartment, leading to hemoconcentration and rise in hematocrit (Ht). The release into the general circulation of the red cells contained in the spleen also contributes to this hemoconcentration. In the well trained endurance athletes total blood volume is expanded. Plasma volume increases more than red cell mass, resulting in a hemodilution that limits the rise of Ht in acute exercise. In this study we have monitored Ht and plasma viscosity changes during maximal aerobic exercise to verify if hemoconcentration is influenced by sex and training and if it occurs during the whole exercise. Twenty healthy volunteers, 10 males and 10 females, performed a maximal aerobic exercise on a cycle ergometer. Ht increased significantly during exercise (F=54.3, p<0.0001). Ht curves in males and females were parallel. Plasma viscosity increased too (F=3.62, p=0.08). No difference was found in Ht and plasma viscosity between trained and untrained subjects. An interesting trend, an hemodilution in the early phases of exercise, didn't result significantly. Acute aerobic exercise leads to Ht and plasma viscosity changes that are not influenced by sex and training and probably represented an adaptation to blood volume variations. Verf.-Referat