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Hydration and Exercise: Drink to Your Health
May 02, 2012
Fluid intake is a really important consideration when exercising. Hydration should not be overlooked and should be a key element of any exercise or sporting activity. Water, a vital nutrient, makes up approximately 65 percent of our body. Drinking the right amount of fluids before, during and after every physical activity is vital to ensure proper hydration and maximum performance.
Dehydration
Water is essential for good health, yet needs vary by individual. The Institute of Medicine determined that to compensate for everyday losses men should intake about 3 liters (13 cups) of fluid per day and women around 2.2 liters (9 cups) of fluid per day. However, if you exercise your fluid needs go up. During exercise, dehydration results when an individual does not adequately replace lost fluids. Studies have found that athletes that lose as little as two percent of their body weight through sweating have a drop in blood volume which causes the heart to work harder, and effects performance.
Early signs of dehydration include:
- thirst
- flushed skin
- premature fatigue
- increased body temperature
- faster breathing and pulse rate
- increased perception of effort
- decreased exercise capacity
Later signs include:
- dizziness
- increased weakness
- labored breathing with exercise
Fluid Losses
So, how much fluid do you need during exercise? This of course varies by individual (body size, gender and fitness level), the length and intensity of the workout and the conditions such as air temperature and altitude. All of these factors will affect the amount of fluid you will lose through sweat. In general, larger people sweat more and men usually sweat more than women. Well-trained athletes also sweat more than less fit people. The longer and more intense the work out, the more fluid loss and as the temperature and humidity levels rise, so will your sweat loss.
Monitoring Hydration Status
Hydration status can be monitored by urine color, daily body weight and sweat loss. If you are producing large amounts of straw or light colored urine it usually means you are well hydrated, on the contrary if you are producing smaller amounts of dark urine it could mean you are dehydrated. Daily weights are useful for monitoring daily fluid losses because total body water changes little under normal conditions. The change in body weight before and after exercise is used to determine sweat loss. Once you know how much you are losing through sweat, you can better determine your fluid requirements. Many athletes follow customized fluid replacement plans.
Before, During and After
It is important to stay well hydrated throughout the day and that you are well hydrated before your workout. If you are exercising moderately, for less than an hour, water is sufficient; however sports drinks (6-8% carbohydrate) are good options for moderate to high intensity activity lasting longer than 60 minutes. This will help to replenish many minerals that act as electrolytes, such as sodium, calcium, potassium, magnesium and chloride. It also provides carbohydrate for energy to prevent a drop in blood glucose levels.
General guidelines for hydration are as follows:
- Drink 16-20 fl oz, 2-3 hours before exercise
- Drink 8-12 fl oz, 10-15 minutes before exercise
- Drink 3-8 fl oz every 15 minutes during exercise, carry a water bottle with you or make regular water breaks part of your fitness routine
- Drink 20-24 fl oz for every pound of lost body weight, weigh yourself before and after exercise to determine needs
Of course, as stated earlier, needs vary by individual, intensity of workout and conditions. Fluid and sodium losses can also be replaced with watery foods that contain salt like soup and vegetable juice. Potassium and fluid losses can be replaced by eating fruits and vegetables. Sometimes drinking large amounts of straight water can be challenging. Flavoring water with lemon or lime juice are healthy options.
Overhydration
Although a rare condition, overhydration or water intoxication can occur when excessive water consumption leads to hyponatremia, or a decrease in sodium concentration in the blood. This is potentially a life threatening condition and behavioral changes include confusion, drowsiness, nausea/vomiting, muscle cramps and weakness/paralysis. If overhydration is suspected, it is important to seek medical attention. Guidelines for preventing overhydration include not consuming more than one liter of fluid per hour.
Kristen is a Registered Dietitian and Licensed Dietitian Nutritionist. She is a graduate of Cornell University and specializes in vegetarian, pediatric and sports nutrition. She currently resides in Philadelphia with her husband and three boys.
References
1. Academy of Nutrition and Dietetics. (2012). Hydrate Right. Retrieved April 15, 2012 from http://www.eatright.org/Public/content.aspx?id=7084&terms=HYDRATE+RIGH T
2. American College of Sports Medicine. (2011). Selecting and Effectively Using Hydration for Fitness [Brochure] Retrieved April 16, 2012 from http://www.acsm.org/docs/brochures/selecting-and-effectively-using-hydration- for-fitness.pdf
3. Exercise and Fluid Replacement: Position Stand. (2007). Medicine and Science in Sports Exercise, 39, 377-390.
4. Sports, Cardiovascular and Wellness Nutrition. (2009). Exercise Hydration. Retrieved April15, 2012 from http://www.eatright.org/WorkArea/DownloadAsset.aspx?id=6442451299
Kristen Logue RD, LDN
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