SNI: From the standpoint of rehydration, is there an ideal percentage of carbohydrate that is needed when consuming fluids? Is there a combination of carbohydrates that is ideal?
Stacy: In my experience working with athletes, they are so focused on calories that they don’t pay attention to the fact that what they are drinking contributes to FUELING, not HYDRATION.
Let me explain.
In science speak: During prolonged exercise, fluid and salt losses through sweating reduce plasma volume which leads to heart rate drift in association with hyperthermia and reductions in performance. Oral rehydration with water reduces the loss of plasma volume and lessens heart rate drift and hyperthermia. Moreover, the inclusion of sodium in the rehydration solution to levels that double those in sweat (i.e., around 90 mmol/l Na+) restores plasma volume when ingested during exercise, and expands plasma volume if ingested pre-exercise.