2012 Volume 33 Pages 23-32
Endurance athletes have a high incidence of orthostatic intolerance. Although cerebral blood flow （CBF） regulation may determine orthostatic tolerance, the influence of endurance exercise training on dynamic cerebral autoregulation （CA） remains controversial. The aim of the present study was to test our hypothesis that dynamic CA would be attenuated in high fit athletes compared with average fit subjects. Sixteen healthy men were assigned to two distinct groups, average fit （AF; maximal oxygen uptake 40 ml/min/kg, n=8） and high fit （HF; 64 ml/min/kg, n=8），based upon their current history of endurance exercise training. We identified dynamic CA in both groups at upright seated position by measuring the responses of arterial blood pressure and middle cerebral artery blood velocity, which was assessed using transcranial Doppler, to a rapid deflation of bilateral super-systolic thigh cuffs. However, there was no significant difference in the rate of regulation （RoR） between AF （0.096±0.107/s） and HF （0.088±0.075/s） subjects （P=0.878）．Contrary to our initial hypothesis, these findings suggest that dynamic CBF regulation unlikely contributes to an endurance exercise training-induced orthostatic intolerance.
