Staying hydrated is critical to your running performance and, more importantly, for preventing heat-related illnesses. Dehydration in athletes may lead to fatigue, headaches, decreased coordination, and muscle cramping. Other heat-related illnesses, such as heat exhaustion and heatstroke, have even more serious consequences.
Runners need to pay attention to what and how much they’re drinking before, during, and after exercise. Whether you’re a casual runner or training for a marathon, here’s some basic advice on proper hydration for running.
Pre-Run Hydration
If you’re doing a long run or race (more than 8 to 10 miles), it’s important to make sure you’re well-hydrated during the few days leading up to your long run. You know you’re well-hydrated if you void large volumes of pale urine at least six times a day.
In the days leading up to your long run (or race), drink plenty of water and nonalcoholic fluids. Not only does alcohol dehydrate you, but it can also prevent you from getting a good night’s sleep. It’s not a good idea to run with a hangover because you’ll most likely be dehydrated when you start running.
An hour before you start your run, try to drink about 16 ounces of water or other non-caffeinated fluid. Stop drinking at that point, so that you can void extra fluids and prevent having to stop to go to the bathroom during your run.
To make sure you’re hydrated before you start running, you can drink another 4 to 8 ounces right before you start.
Drinking on the Run
The current advice about running and hydration is very simple — try to drink to thirst. Scientific evidence says that drinking when you’re thirsty can help prevent underhydrating (which can lead to dehydration) and overhydrating, which can lead to hyponatremia (low blood salt level due to abnormal fluid retention).
If you’re looking for a general rule of thumb for fluid consumption during your runs: You should take in 4 to 6 ounces of fluid every 20 minutes during your runs. Runners running faster than 8-minute miles should drink 6 to 8 ounces every 20 minutes.
During longer workouts (90 minutes or more), some of your fluid intake should include a sports drink (like Gatorade) to replace lost sodium and other minerals (electrolytes). The carbohydrates and electrolytes in the sports drink also help you absorb the fluids faster and may prevent muscle cramps.
Runners who don’t sufficiently replace electrolytes during long runs or races can risk over-hydration. Hyponatremia can occur when athletes drink excessive amounts of water and don’t replace salt lost through sweat.
Another benefit of sports drinks is that they contain carbohydrates. Since it’s necessary to consume calories during runs of longer than 90 minutes, drinking a sports drinks will help you take in some of these needed calories. Some runners find that it’s sometimes easier to get their calories through liquids rather than solid foods, especially during the later stages of a long run or race.
During runs of more than 90 minutes, you can alternate between sports drinks and water. So, every other hydration break, you should be drinking a sports drink. For shorter runs, hydrating with plain water is fine.
If you don’t have access to water on your running routes, you’ll have to carry your own fluids with you. From running belts to hand-held water bottles to hydration backpacks, there are plenty of options for carrying fluids with you on the run.
However, if you’re running in a race, you don’t have to carry your own fluids because they should have water stops on the course.
Should I Drink Lukewarm or Cold Water?
The idea that you’ll get cramps from cold water is a myth. Cold water is actually absorbed in the body quicker than warm water. Drinking water, whether it’s warm or cold, before or during running should not give you cramps. The best ways to prevent side stitches while running is to make sure you warm-up properly and to breathe deeply through your mouth.
Faster absorption is not the only benefit of drinking cold water during runs. Drinking cold water during a hot run also makes you feel cooler. And the effect is not just psychological. The cold water also produces a slight physiological cooling effect, which is obviously important when running in hot weather.
It’s not always easy to keep your water cold during hot weather runs. It helps to use a hand-held water bottle with an insulated cover so the warmth from your hands doesn’t immediately warm up the water.
You can also put ice in your water bottle or partially freeze your water bottle before your runs so the water stays cold as the ice melts.
Determining Your Sweat Rate
The above hydration guidelines are the basic rules of thumb, but it’s important to remember that everyone’s fluid needs vary. Some people sweat more than others.
To determine how much liquid to take during a run or race, you need to know your sweat rate, and that can vary between 1 to 4 quarts per hour. Weigh yourself nude before a timed training run, and then again after. One pound of weight loss equals 1 pint of water loss.
Calculate your sweat rate and use this information to determine your fluid needs during a run or race. For example, if you lose 2 pounds during an hour run, that’s 2 pints or 32 ounces. Thus, you need 8 ounces of water or sports beverage every 15 minutes.
Note the weather conditions on that day, and keep in mind that you may need to adjust your consumption if the conditions are different. You can do the sweat rate test on another day to see how different conditions affect your sweat rate.
Post-Run Hydration
Don’t forget to rehydrate with water or a sports drink after your run. You should drink 20 to 24 fl oz. of water for every pound lost. If your urine is dark yellow after your run, you need to keep rehydrating. It should be a light lemonade color.
Running coach, avid runner, and fitness writer Christine Luff is an RRCA-certified running coach and ACE-certified personal trainer. Founder of the website Run for Good and author of the book Run for Good: How to Create a Lifelong Running Habit, she coaches runners, from beginners to advanced, who are training for races, from 5Ks to marathons.
