Fluid Absorption Rate
First, it’s important you understand how sugar and electrolytes impact your fluid absorption rates. The speed at which water, electrolytes, and sugars can be absorbed into the blood stream is one of the main determinants of what type of beverage you should choose when trying to stay hydrated.
The absorption of fluids into the body is largely dependent upon two factors: 1. the rate at which it is absorbed through the walls of the small intestine; and 2. the speed at which it is emptied from the stomach. Both of these factors are controlled by the composition of a liquid in terms of its carbohydrate (sugar), and electrolyte concentrations.
As a general rule, the higher the carbohydrate content of your beverage, the slower the absorption rate will be. Consequently, trying to maintain proper hydration and balanced electrolyte levels during a run with sugary sports drinks is difficult. On the other hand, plain water passes through the body too quickly without providing the necessary sugar to spark the insulin response and ignite the recovery process.
Puts you in a bit of a pickle, right?
Your choice for hydration will depend on whether your primary aim is rehydration (keeping the body cool and maintaining fluid balance) or the replenishment of energy (restocking sugar and electrolyte stores).