I'll try that, AG! You wouldn't believe how many times I've had to grab furniture to steady myself.
GHOSLO is right. Both younger athletes and older everyones can experience it. And GHOSLO is an athlete, which probably doesn't help in this situation.
I found this interesting too:
"Also, a delayed onset of autoregulation in the trained subjects could be related to higher cerebrovascular tone (basal state of vasoconstriction), which could make the cerebral vessels of these subjects more vulnerable to a rapid reduction in blood pressure (although that higher cerebrovascular tone could, on the other hand, protect them from surges in arterial pressure such as during exercise)."