Whether you’re exercising outdoors, working in the yard, or lying out by the pool this summer, it’s important to replace lost fluids and stay hydrated.

The amount of fluid that needs to be replaced depends on the individual, and the degree of activity. But there’s some confusion and outright myths about what to drink, how much to drink, and when. We’ve done the research for you and compiled these tips from the experts:

What to drink:

• For most people doing light to moderate activity outdoors, plain water is best to replace lost fluids and prevent dehydration.
• Sports drinks are generally preferred over water only when exercising at a high intensity, for a long duration of time and/or in high temperatures. Sport drinks contain sodium that enables the body to retain fluid that is lost through sweat. They also provide calories to help replace energy lost during exercise. Drinking plain water throughout the day is still encouraged in addition to sports drinks during long periods of intense exercise.
• The National Athletic Training Association (NATA) recommends that sports drinks should be below eight percent in carbohydrate content. Any more than this will impede the rate of fluid emptying from the stomach and absorbed by the intestine. This is why high sugar drinks such as soda or juice are not the best liquids to replace lost fluids.
• Since sports drinks are intended for intense exercise, they are high in carbohydrates (mostly sugars) which can lead to weight gain if consumed for light or moderate physical activity.
• Avoid drinks that contain caffeine or alcohol, which actually promote fluid loss.

How much and when to drink fluids:

• The Institute of Medicine suggests that men consume around 13 cups of total fluids a day and women consume about 9 cups, which includes water from other beverages as well as high-water containing foods. A good indicator of hydration is to drink enough fluid so that the body does not feel physically thirsty and so that it produces regular, light-colored urine.
• For more immediate re-hydration, drink cool, not cold water, as cool water is more readily absorbed.
• To replace lost fluids during outdoor activity, follow these guidelines from the Texas Heart Institute to prevent dehydration and heat stroke.

For workouts of less than 1-1/2 hours, you should:

• Drink about 16 ounces of cool or cold water 1 to 2 hours before you exercise.
• Drink about 16 ounces of cool water or a sports drink 15 minutes before you exercise.
• Drink about 5 ounces of cool water every 10 minutes during exercise.
• Drink about 16 ounces of cool or cold water or a sports drink just after exercise.

For longer or more intense exercise:

• Follow the guidelines above plus have about 34 ounces of cool water on hand per hour of physical activity. About every 1-1/2 to 2 hours, a sports drink may be substituted for water during more vigorous exercise or if the weather is very hot or humid.

• Feeling thirsty is not the best indicator of your body's water needs, because thirst occurs after your body is already dehydrated. Also, your thirst is usually satisfied even before your body's water supply is fully replaced. This means that during workouts, you should drink water even if you do not feel thirsty.

Watch for these warning signs:

If you experience any of these symptoms:  weakness, headache, dizziness, muscle cramps, nausea or vomiting or rapid heartbeat, stop what you’re doing and get out of the heat. Drink water and wet or fan your skin. If you don’t feel better within an hour, call your doctor. If you develop a fever higher than 102 F or become faint or confused, call 911 or seek immediate medical attention. You may be suffering from heat stroke which can cause irreparable body damage or death.

Sources:

LiveStrong

Mayo Clinic

Texas Heart Institute