When it comes to sports drinks, Fishman prefers skipping the sugary solutions and sticking with coconut water. "Sports drinks are helpful for athletes who sweat a lot and need to rehydrate quickly so they can exercise again within the next 12 hours," adds Scritchfield. "For most active people who will not exercise again that day, most fluids and electrolytes can be replaced with a healthy, balanced diet and plain water."
More: Don't Let Your Sports Drink Become a Crutch
When to Drink
Getting past that 100 percent mark of replacing fluids lost through sweat takes careful orchestration throughout the day. Scritchfield points to Nancy Clark's Sports Nutrition Guidebook as the best source to answer these types of questions.
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"For pre-workout hydration, the goal is to drink 5 to 7mL (30mL is about 1 ounce) per .5 pounds of body weight at least four hours before exercising," she explains. This means that a 150-pound runner should drink between 10 to 15 ounces of fluid at least four hours before working out. The closer you get to the run, the less you should drink so you don't have a belly full of water sloshing around. If you're a morning runner, this amount will be reduced since you have less time to drink.
For runs that last 45 to 60 minutes in warmer temperatures, you should also plan on hydrating during your run. The International Marathon Medical Directors Association simply suggests drinking when you're thirsty. This is largely as a result of hyponatremia. A number of serious conditions, like liver and kidney failure, have been linked to this phenomenon, which occurs when someone drinks so much water that he throws off the electrolytes in his system—effectively diluting the sodium levels in his blood. This is why it is best to simply take in water or a sports drink as needed, rather than forcing yourself to drink on the run.
Post-run, the focus is all about getting back to equilibrium, since it's impossible to stay completely hydrated during a longer run. "After working out, the goal is to fully replenish any fluid losses," says Scritchfield. "It is recommended to drink frequently for 12 to 24 hours after a long or hard workout."
More: Best Long Run Hydration Habits
This is the time to look back at your average sweat rate and consume as much as necessary to top off fluid stores. After weighing yourself before and after your runs in a number of weather conditions, you should be able to rely on an average amount you need to consume.
"The better we feel both physically and mentally, the better we perform, and hydration is a big part of that," adds Fishman. "You can still be a good runner even if you are slightly dehydrated, but you won't be maximizing your abilities."
Put simply, with an individualized approach to hydration, who knows how much faster you might be?
More: How Do I Run a Faster 5K?
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