Whether you’re a serious athlete or simply exercise for recreation, it’s important to stay hydrated. Good hydration means getting the right amount of water before, during, and after exercise. Water regulates your body temperature and lubricates your joints. It helps transport nutrients to give you energy and keep you healthy. If you’re not hydrated, your body can’t perform at its highest level. You may feel tired, have muscle cramps, dizziness, or other serious symptoms.
Path to improved health
A simple way to make sure you’re staying properly hydrated is to check your urine. If your urine is usually colorless or light yellow, you are most likely well hydrated. Dark yellow or amber-colored urine can be a sign of dehydration.
How much water should I drink while exercising?
There are no exact rules for how much water to drink while exercising, because everyone is different. You need to consider factors including your sweat rate, the heat and humidity in your environment, and how long and hard you are exercising.
The American Council on Exercise has suggested the following basic guidelines for drinking water before, during, and after exercise:
- Drink 17 to 20 ounces of water 2 to 3 hours before you start exercising.
- Drink 8 ounces of water 20 to 30 minutes before you start exercising or during your warm-up.
- Drink 7 to 10 ounces of water every 10 to 20 minutes during exercise.
- Drink 8 ounces of water no more than 30 minutes after you exercise.
Athletes may want to measure how much fluid they lose during exercise to get a more specific measurement of how much water to drink (16 to 24 ounces of water for every pound of body weight lost).
What about sports drinks?
For most people, water is all that is needed to stay hydrated. However, if you will be exercising at a high intensity for longer than an hour, a sports drink may be helpful. The calories, potassium, and other nutrients in sports drinks can provide energy and electrolytes to help you perform for a longer period of time.
Choose a sports drink wisely. They are often high in calories from added sugar and may contain high levels of sodium. Also, check the serving size. One bottle may contain several servings. If you drink the entire bottle, you may need to double or triple the amounts given on the nutrition facts label. Some sports drinks contain caffeine. If you consume a sports drink that contains caffeine, be careful not to add too much caffeine to your diet. Caffeine may cause a diuretic effect on your body. This means that you may have to urinate more often.
Things to consider
Dehydration happens when you lose more fluid than you drink. When your body doesn’t have enough water, it can’t work properly. Dehydration can range from mild to severe. Symptoms of dehydration can include the following:
- Dizziness or lightheaded feeling.
- Nausea or vomiting.
- Muscle cramps.
- Dry mouth.
- Lack of sweating.
- Hard, fast heartbeat.
Symptoms of severe dehydration can include mental confusion, weakness, and loss of consciousness. You should get emergency medical attention immediately if you have any of these symptoms.
What is heat illness?
Heat illness can occur when your body is dehydrated and can’t cool itself effectively during exercise in hot or humid weather. There are 3 stages of heat illness:
- heat cramps
- heat exhaustion
- heatstroke
Symptoms of heat cramps include painful muscle spasms in the legs, stomach, arms, or back. Symptoms of heat exhaustion are more serious. They can include faint or weak feelings, nausea, headache, fast heartbeat, and low blood pressure.
The most serious heat-related illness is heatstroke. Symptoms can include high body temperature (higher than 104°F), fast heartbeat, flushed skin, fast breathing, and possibly even delirium, loss of consciousness, or seizures. You should get emergency medical attention immediately if you experience any of the symptoms of heatstroke. Untreated heatstroke can lead to death.
How much water is too much?
This depends on your body and the kind of activity you are doing. Talk to your family doctor if you have questions about the right amount of water to drink while exercising.
When to see a doctor
You should see a doctor immediately if you have symptoms of dehydration, heat exhaustion, or heatstroke. You should also see a doctor if you have symptoms of a rare condition called hyponatremia. These include confusion, headache, vomiting, and swelling of the hands and feet.
That's not always the case for ultra-endurance athletes who spend long hours exercising. Sometimes, drinking too much water can actually be a problem. If they flood their bodies with excess water, they may fall victim to a potentially fatal condition called hyponatremia.
Causes of Hyponatremia
Hyponatremia is low sodium concentration in the body, specifically the extra-cellular fluid, which is the blood and the fluid around the body's cells.
Normal sodium levels run between 135-145 milliequivalents per liter (mEq/L). Hyponatremia is generally defined as a sodium level of 135 mEq/L or below.
When sodium concentration in the blood is critically low, symptoms like muscle weakness, disorientation, headache, fatigue, and nausea may occur. The most severe symptoms include seizures, respiratory arrest, coma, and death.
When Hyponatremia Is Likely
Hyponatremia is more likely to occur in the following situations:
- Environments that are extremely hot
- During long distance endurance events such as marathons, ultra-marathons and triathlons
- During events that require high effort
Who Is Most at Risk for Hyponatremia?
Ultra-Endurance Athletes
Ultra-endurance athletes who enter such events as 100-mile races and Ironman competitions are most at risk. Hyponatremia can occur as early as 4 hours into an event, but it's more likely to happen after 6 to 10 hours of exercise.
Other Endurance Athletes
Non-elite marathon runners are also at risk. A study in the New England Journal of Medicine found that out of 488 runners who volunteered blood samples after completing the Boston Marathon, 13% had hyponatremia and 0.6% had critical hyponatremia. Risk factors for developing hyponatremia included: gaining substantial weight during the race, having a racing time greater than 4 hours, and having a low or high body mass.
How Can Endurance Athletes Prevent Hyponatremia?
Say Yes to SaltChoose Drinks WiselyWeigh InEndurance athletes need to take preventive measures to head off hyponatremia. It's best to plan in advance how you will stay hydrated safely.
Ultra-endurance athletes may want to consider adding more salt to their diets so they begin events with a good supply of sodium. This is not necessary for most recreational athletes, since most diets typically contain enough sodium to make up for that lost when sweating.
All athletes should drink water before their events, but when you've been exercising for more than an hour, sports drinks or other fluids with sodium are better choices.
Experts disagree on how much fluid to drink during endurance events. One recommendation is to consume 5-10 ounces (150-300 milliliters) of fluid every 15-20 minutes. However other experts recommend that athletes avoid exceeding 13-26 ounces (400-800 millileters) per hour. As you gain experience, you will begin to know your own fluid needs and drink accordingly.
Athletes should weigh themselves before and after their long-distance events. In fact, some long-distance events may require that you do so. In most cases, dehydration is more likely to be a problem than hyponatremia. By weighing themselves, athletes will know if they're drinking too much or too little.
Checking body weight at the same time every day before and after an endurance event will help athletes gauge how much fluid they need to replace or if they've consumed too much fluid.
Resources
American College of Sports Medicine
//www.acsm.org
American Running Association
//www.americanrunning.org
Canadian Resources
Canadian Society of Exercise Physiology
//www.csep.ca
Health Canada
//www.canada.ca
References
Almond CSD, Shin AY, Fortescue EB, et al. Hyponatremia among runners in the Boston Marathon. N Engl J Med. 2005;352(15):1550-1556.
Cosca DD, Navazio F. Common problems in endurance athletes. Am Fam Physician. 2007;76(2):237-244.
Hyponatremia. EBSCO DynaMed Plus website. Available at: //www.dynamed.com/topics/dmp~AN~T113706/Hyponatremia. Updated January 20, 2016. Accessed October 10, 2017.
Hyponatremia. University of Connecticut website. Available at: //ksi.uconn.edu/emergency-conditions/hyponatremia. Accessed October 10, 2017.
Seebohar B. Hyponatremia in endurance athletes. Team USA website. Available at: //www.teamusa.org/USA-Triathlon/News/Blogs/Fuel-Station/2010/August/02/Hyponatremia-in-Endurance-Athletes. Accessed October 10, 2017.