Abstract des Autors

No significant change in total cerebral blood flow (total CBF) may be shown during physical exercise, although marked modifications in blood pCO2, pO2, pH and in some general hemodynamic parameters are present. However, it should be stressed that during exercise the total cerebro-vascular resistance markedly increases, in contrast with a well-known large decrease in the peripheral vascular resistance. Moderate physical exercise produces selective slight increase in blood flow to brain regions associated with motor-sensory activation and control. Although the CBF of any other region tested remains unchanged, during physical effort the vascular resistance increases in all regions of the brain, except the above-quoted one (related to motor-sensory activation and control) in which vascular resistance is unchanged. In all brain regions, tissue hematocrit value is markedly lower than the hematocrit one of the peripheral large vessels. The overall effect seems to be a protective one, preventing an overshooting rise in cerebral blood viscosity particularly in brain regions in which the vascular resistance increases during exercise. Thus, possibly middle-Iong-term damage induced in these brain areas by the increased cerebral blood flow viscosity in blood-doped athletes should be feared. Therefore, the blood-doping is an unphysiological method that acts against the protective cerebral blood-dilution and that exposes the athletes to the risk of cerebral damages. Verf.-Referat