Try a Sports Drink Research shows that sports drinks can improve performance in races as short as an hour. See if one works for you. It's a fair question, especially if you've ever had that feeling of fluid swilling around in your stomach during a race and wondered if it would ever get absorbed. To answer your query, when exercise intensifies, yes, things do slow down, but they don't come to a halt. Let me explain.
Fluid replenishment is a two-part process.
When you drink water or a sports beverage, the fluid first goes into the stomach, where it then gets metered into the small intestine. But it's during the first part of this process, in the stomach, that fluid gets held up because of intense exercise. This probably happens because blood is diverted away from the stomach to hard-working muscles. How much the process slows down is hard to determine, as research shows that runners vary widely in their rates of stomach emptying and fluid absorption. Generally, you absorb between 3 and 4 cups of fluid per hour, and somewhat less during very intense exercise.