This article is from the Aerobics Fitness FAQ, by email@example.com (Robles) with numerous contributions by others.
While the body's reliance on carbohydrates increases during
high-intensity activity, it's not that fat burning is in any
way inhibited. It's just that the rate of increase in the amount
of fat burned is slower than the rate of increase in the amount of
carbohydrate used. So the percentages change, but the aerobic
metabolism (fat burning) isn't really inhibited. Again, those
minute-to-minute fluctuations are insignificant in the grand