During the blazing days of summer, you need more than sunscreen to protect your body from the sun. "Hydration becomes most important during intense exercise in the heat," says Douglas Casa, PhD, who heads the University of Connecticut's Korey Stringer Institute, which studies heatstroke and other causes of sudden death in sports. "If you're not adequately hydrated, your blood volume drops, which means your heart has to work harder to power your muscles and keep you cool. When that happens, your running performance suffers." (Search: What are warning signs of a heatstroke?)
While staying hydrated is important during exercise, it's impossible to create one-size-fits-all drinking guidelines. Every runner's needs are different. Your body weight, sweat rate, and effort level, along with the temperature, humidity, and elevation, affect how much you should drink. That doesn't mean you should leave your hydration plan up to chance. These strategies can help ensure you drink the right amount before, during, and after every run.
Learn about everything you need to fuel your workouts in the Runner’s World Eat Like a Genius Guide.
Before Your Run
One of the best ways to limit dehydration during a run is to drink enough before it. (Video: Proper running hydration) "Checking your urine prerun is an easy way to see if you're hydrated," says Lewis Maharam, MD, former medical director of the Rock 'n' Roll race series. "If it's clear, you're drinking too much. If it's the color of iced tea, you need to drink more. If it's a pale lemonade or straw color, you're nicely hydrated."
How much you should drink depends on how soon you'll be running, what your stomach can tolerate, and how dehydrated you are. "Typically, most people can handle six to eight ounces right before a run," says Heidi Skolnik, MS, CDN., owner of Nutrition Conditioning in New York City. With the exception of alcohol, which is dehydrating, all beverages, including water, sports drink, coffee, tea, juice, and milk, can help keep you hydrated throughout the day.
If you find you're often dehydrated before a run, make sure to have a beverage with all your meals. "The fluid you drink helps you absorb the water content in whatever you eat," says Skolnik.
Best Pre-Run Snacks
During Your Run
If you're headed out for an 18-miler, drinking midrun is a no-brainer. But what if you're going for an hour? Or doing 45 minutes of intervals? "There have been a range of recommendations over the past two decades," says Maharam. "The newest brings us back to basics: Drink to your thirst." It's advice backed up by the International Marathon Medical Directors Association and Tim Noakes, MD, author of Waterlogged: The Serious Problem of Overhydration in Endurance Sports. "Your thirst mechanism is exquisitely tuned to your body," says Dr. Noakes. "Some runners get thirsty quickly; others can go hours without feeling the need to drink much. If you drink when you're thirsty, you'll stay adequately hydrated." That said, Casa and Skolnik suggest always drinking on runs 90 minutes or longer.