Drinking Water During Exercise

The Well-Watered Exerciser

Except for oxygen, there’s nothing your body needs more than an adequate supply of water. And the more you exercise, the more important it is to drink the right amount of water before, during, and after your workouts. Dehydration can make it hard to get the most out of your workout, and in extreme situations, can even be dangerous to your health. However, drinking too much water at the wrong time can also hinder performance.

So what’s an exerciser to do? How do you know how much you need to drink, when to drink it, and when you might need something other than plain water, like a sports drink? Obviously, people differ a lot in body size, how much they sweat, the type and amount of exercise they do, and the climate in which they exercise. All these factors make one-size-fits-all recommendations on drinking water ineffective or even dangerous. An approach used by competitive marathoners in hot, humid weather isn’t going to make much sense for you if you’re jogging or walking for 30 minutes on a treadmill in an air-conditioned gym (or vice-versa). Therefore, a competitive athlete could benefit greatly from an assessment of individualized fluid, electrolyte and energy needs by a Registered Dietitian with experience in sports nutrition.

Do you need to worry about drinking during exercise?
The good news is that staying hydrated during exercise really isn’t complicated for most people. If your typical exercise session is around 60 minutes or less, and doesn’t involve vigorous activity outdoors in hot, humid weather, you probably don’t need to interrupt your exercise session for a drink unless you prefer to. A healthy, average-sized person can produce as much as 32 oz of sweat during an hour of moderate to vigorous indoor exercise. That may feel and look like a lot of sweating, but it shouldn’t be enough to cause problems unless you’ve been seriously short-changing yourself on fluid intake prior to starting your exercise. You can tell whether that’s a potential problem by checking your urine color before exercise. If it’s dark yellow with a strong urine smell, it’s a good idea to have a cup or two of water 30-60 minutes before you start exercising. If it’s clear to light yellow, it should be fine to just rehydrate gradually after your exercise session without worrying about stopping to drink during the middle of it.

According to the American College of Sports Medicine, dehydration is likely to start affecting exercise performance when sweating causes you to lose 2% or more of your normal (hydrated) body weight. That's more than 51 ounces, or a little over 3 pounds, for an "average" person of 160 pounds. At this level of mild dehydration, you’ll probably be a little thirsty (though many people don’t experience thirst until they’re already dehydrated), and you may start to feel as if you have to work significantly harder to maintain your performance level. As dehydration gets progressively more severe, you may start to feel lightheaded, uncoordinated, or have muscle cramps. If you continue, you may start experiencing the symptoms of heat exhaustion, and that can progress to heat stroke, which is potentially fatal and needs immediate medical attention.

The goals of fluid intake during exercise are to prevent dehydration from occurring and to not drink in excess of one’s sweating rate. One good way to figure out whether you need to drink something during your workout is to simply weigh yourself (without clothes) just before and after a typical workout. If your weight change is more than 2% of your starting weight, then in the future, you should plan to drink enough water during your workout to keep your post-workout weight within that 2% range. Typically, drinking a cup (8 oz) of water every 15-20 minutes will do the trick in all but the most extreme situations. While difficult to recommend a specific fluid schedule because of varying needs, this handy chart provides some basic guidelines:

Drink Water How Much? When?
Before Exercise 8-16 oz At least 15 minutes before workout
During Exercise 4-8 oz Every 15-20 minutes
After Exercise 16-24 oz per pound* lost As soon as possible

*If possible, weigh yourself on the same scale, before and after exercise so you know how much to drink for rehydration.

Special Cases: Long Workouts and Hot Weather
If your workout is particularly long or your environment is hot and/or humid, just drinking plain water during your exercise may not be the best option.

Two hours of vigorous exercise can deplete the fuel supply (called glycogen) that your muscle cells use during vigorous activity. Drinking water alone won’t replenish that fuel. Assuming you can’t take a meal break in the middle of your marathon race, you may need something to drink that also contains carbohydrate for energy and to sustain performance. Commercial sports drinks containing 6% to 8% carbohydrate from various sugar sources are recommended for exercise events lasting longer than 1 hour. Higher carbohydrate amounts should be avoided because they impede the rate at which the drink leaves the stomach thereby slowing down the hydrating benefit. To estimate your carbohydrate need during sustained exercise, aim for about 30-60 grams of carbohydrate per hour of endurance exercise

Likewise, when you sweat heavily for an extended period, you’re not losing just plain water. You’re also losing a significant amount of sodium, which needs to be maintained within a certain range to avoid potentially serious problems like exercise-induced hyponatremia (a serum sodium concentration <130 mEq/L), which can also occur if you drink too much plain water, in a short time period. It isn’t very easy to give yourself hyponatremia: An otherwise healthy person would have to combine hours of heavy sweating with drinking significantly more water than they’re actually losing during the exercise and not replacing the lost sodium. You can avoid this by making sure your water intake during and immediately after exercise is equal to the amount you lose (see above about weighing yourself).

For particularly long endurance workouts OR exercise sessions in hot and humid weather, one may need more than the Tolerable Upper Intake Level for sodium (2,300 milligrams daily). That's why commercial sports drinks are often recommended for athletes taking part in such endurance events. Make sure the sports drink contains about 120–170 milligrams of sodium per 8-ounce serving. If you are looking for a less expensive option for the commercial sports drink, try this simple recipe. You may also need to replace lost sodium by consuming high-sodium foods and beverages following the event. High sodium food choices could include: canned soups, beans and vegetables; boxed side dishes like macaroni and cheese, potato mixes, or rice blends; Oriental style entrees with soy sauce; pizza; jarred spaghetti sauce; salted nuts; and regular cheese.

Following the event, replenish your energy stores using these recommended guidelines.

Everyone knows that athletes must plan and time their meals and snacks very carefully to reach their performance goals. But what about the rest of us? You try to squeeze in 30-60 minutes of exercise most days of the week. Do you have to be careful about what you eat before and after your workouts, too?

If you’re eating a healthy diet and getting enough calories to support your activity level, you can probably rely on your own appetite, energy levels, and experience to tell you whether you need to eat anything before or after exercise and what it should be. The basic rule here is: Find out what works best for you, and do that.

There are some advantages to knowing how your body works and what it needs to perform at its best. The bottom line for healthy weight loss and fitness sounds simple: You have to eat fewer calories than you use up — but not fewer than your body needs to function at its best.

The size, timing, and content of your pre- and post-exercise meals and snacks can play an important role in your energy levels during your workout, how well your body recovers and rebuilds after your workout, and whether the calories you eat will be used as fuel or stored as fat. Here’s what you need to eat and drink to get the results you want!

Your Post-Exercise Fluid Needs
Most moderate exercisers will lose about one quart (4 cups) of fluid per hour of exercise, so try to drink about 16-20 ounces of water shortly after your workout to aid the recovery process. If you sweat a lot or the weather is hot and/or humid, consider weighing yourself before and after exercise, and drinking an ounce of water for every ounce of weight you've lost. Because heavy sweating also causes loss of minerals and electrolytes, consider using a sports drink with electrolytes if you need to replace more than 2-3 cups of fluid.

Your Post-Exercise Meal or Snack
As long as you’re staying within your overall range for the day, you don’t need to be obsessive about matching the following calorie and nutrient ratios perfectly. Just be careful not to fall into the very common trap of thinking that it’s OK to eat anything and everything in sight because you just worked out. Many people are very hungry after a workout, making it easy to eat more than you really need, or choose foods that won’t really help your body. Eating too much of the wrong thing can do the opposite of what you want—cause your body to store that food as fat instead of using your post-workout food to refuel and repair your muscles.

Calories. Ideally, try to eat enough calories to equal 50% of the calories you burned during your workout. So if you burn about 600 calories during your workout, try to eat 300 calories afterward.

Don’t worry about undoing the calorie-burning benefits of your workout–that’s not how weight loss works. As long as you're eating within your recommended calorie range (whether for weight loss or maintenance), you'll be on your way to reaching your goals.

• Carbohydrates. Roughly 60% of the calories you eat at this time should come from carbohydrates. Contrary to popular belief, your body needs more carbohydrates than protein after a workout, to replace the muscle fuel (glycogen) you used up and to prepare for your next exercise session. Moderate exercisers need about 30-40 grams of carbohydrates after an hour of exercise, but high-intensity exercisers need more—around 50-60 grams for each hour they exercised.

If you have some favorite high-carb foods that are lacking in the whole grains and fiber that are often recommended as part of a healthy diet, this is a good time to have them! Your body can digest refined carbohydrates faster during your "refueling window," but if you’re a whole foods foodie, don’t force yourself to eat processed foods.

• Protein. While carbs are essential, it’s also important to include some high-quality protein in your post-workout meal or snack. This protein will stop your body from breaking down muscle tissue for energy and initiate the process of rebuilding and repairing your muscles. About 25% of the calories you eat after a workout should come from protein—that's about 10-15 grams for most people.

• Fat. Fat doesn't play a big role in post-workout recovery, and eating too much fat after a workout won't help your weight control or fitness endeavors. Only 15% (or less) of your post-workout calories should come from fat—that's less than 10 grams.

The ideal time to eat after a workout is within 30 minutes to two hours, when your body is ready and waiting to top off its fuel tanks to prepare for your next workout

But if your appetite or schedule doesn’t allow you to eat a meal right after your exercise session, don’t panic. Your body can still replace your muscle fuel over the next 24 hours, as long as you’re eating enough food to support your activity level. If you can, have a smaller snack that contains carbs and protein as soon after exercise as possible. Liquids like smoothies, shakes, or chocolate milk, and/or energy bars can be especially effective snacks after a workout.

Here are some sample food combinations for your post exercise meal: • Bread, a bagel, or an English muffin with cheese or peanut butter

• Dried fruit and nuts
• Cottage cheese with fruit
• Fruit juice with cheese
• Yogurt with fruit
• Veggie omelet with toast or roll
• Chocolate milk
• Cereal with milk
• Eggs and toast

• Turkey, ham, chicken, or roast beef sandwich
• Vegetable stir-fry with chicken, shrimp, edamame or tofu
• Crackers with low fat cheese
• Rice or popcorn cakes with nut butter
• Smoothie (with milk, yogurt, or added protein powder)
• A protein or energy bar
• A protein or energy shake
• Pancakes and eggs
• Any regular meal that contains lean protein, starch, and vegetables