.

Drink plenty of liquids before, during and after workouts and competitions.

Dehydration can affect a swimmer's performance in less than an hour of exercise, even sooner if you begin the session dehydrated.

And yes, you DO sweat and can become dehydrated during a good workout in a swimming pool.

Dehydration of just one to two percent of body weight can negatively influence performance. Dehydration of greater than three percent of body weight increases an athlete's risk of heat illness (heat cramps, heat exhaustion, heat stroke).


Signs & symptoms of dehydration

Mild Dehydration

  • Fatigue and/or loss of energy.
  • Headache or body ache.
  • Thirsty.
  • Dry mouth.
  • Urine is dark colored.
  • Irritability.
  • Dizziness.

Moderate Dehydration

  • Very dry mouth.
  • Diminished amount of urine.
  • Weakness.
  • Increased dizziness.
  • Skin is less firm.
  • Rapid and weak pulse.
  • Nausea.
  • Changes in mental state (disorientation/memory loss).

Severe to Life-threatening Dehydration

  • Loss of consciousness.
  • Sunken looking eyes.
  • Extremely dry mouth and cannot swallow.
  • Swollen tongue.
  • Delirium.


Recommendations for Hydration to Prevent Heat Illness

from the Journal of Athletic Training: 35(2): 212-224; NFHS Handbook Heat Related Illness, Sandra Shultz Phd, ATC, CSCS, Steven Zinder MS, ATC


TYPES OF SPORTS DRINKS TO DRINK

Fluid Replacers

Examples: Water, Gatorade, 10K, Quickick, Max
 
These drinks are absorbed as quickly as water and typically are used for activities lasting less than 2 hours.

Carbohydrate loaders

Examples: Gatorlode, Exceed High, Carboplex
 
These drinks replace more muscle glycogen to enhance greater endurance. They should be used after ultra-endurance events to increase muscle glycogen resynthesis after exercise.

Nutrition Supplements

Examples: Gatorpro, Exceed Sports, Ultra Energy
 
These supplements are fortified with vitamins and minerals and they help athletes maintain a balanced diet. They can be used as a meal replacement supplement for athletes who wish to skip a high fat meal, or as extra calories for athletes who wish to gain weight.

WHAT NOT TO DRINK

Drinks with Carbohydrate (CHO) concentrations of greater than eight percent should be avoided.
 
Fruit juices, CHO gels, sodas, and sports drinks that have a CHO greater than six to eight percent are not recommended during exercise as sole beverages.
 
Beverages containing caffeine, alcohol, and carbonation are not to be used because of the high risk of dehydration associated with excess urine production, or decreased voluntary fluid intake.


RECOMMENDATIONS TO PREVENT HEAT ILLNESS

Drink according to a schedule based on individual fluid needs.
 
Drink before, during and after practices and games.
 
Drink 17-20 ounces of water or sports drinks with six to eight percent CHO, two to three hours before exercise.
 
Drink another 7-10 ounces of water or sport drink 10 to 20 minutes before exercise.
 
Drink early - By the time you're thirsty, you're already dehydrated.
 
In general, every 10-20 minutes drink at least 7-10 ounces of water or sports drink to maintain hydration, and remember to drink beyond your thirst.
 
Drink fluids based on the amount of sweat and urine loss.
 
Within two hours, drink enough to replace any weight loss from exercise.
 
Drink approximately 20-24 ounces of sports drink per pound of weight loss.
 
Dehydration usually occurs with a weight loss of two percent of body weight or more.


WHAT TO DRINK DURING EXERCISE

If exercise lasts more than 45-50 minutes or is intense, a sports drink should be provided during the session.
 
The carbohydrate concentration in the ideal fluid replacement solution should be in the range of six to eight percent CHO.
 
During events when a high rate of fluid intake is necessary to sustain hydration, sports drinks with less than seven percent CHO should be used to optimize fluid delivery. These sports drinks have a faster gastric emptying rate and thus aid in hydration.
 
Sports drinks with a CHO content of 10 percent have a slow gastric emptying rate and contribute to dehydration and should be avoided during exercise.
 
Fluids with salt (sodium chloride) are beneficial to increasing thirst and voluntary fluid intake as well as offsetting the amount of fluid lost with sweat.
 
Salt should never be added to drinks, and salt tablets should be avoided.
 
Cool beverages at temperatures between 50 to 59 degrees Fahrenheit are recommended for best results with fluid replacement.


EFFECTS ON PERFORMANCE AND RELATIONSHIP TO HEAT ILLNESS

Dehydration can affect an athlete's performance in less than an hour of exercise - sooner if the athlete begins the session dehydrated.
 
Dehydration of just one to two percent of body weight (only 1.5-3 lb.. for a 150-pound athlete) can negatively influence performance.
Dehydration of greater than three percent of body weight increases an athlete's risk of heat illness (heat cramps, heat exhaustion, heat stroke).
 
High-body-fat athletes can have a harder time with exercise and can become dehydrated faster than lower-body-fat athletes working out under the same environmental conditions.
 
Poor acclimatization/fitness levels can greatly contribute to an athlete's dehydration problems.
 
Medications/fevers greatly affect an athlete's dehydration problems.
 
Environmental temperature and humidity both contribute to dehydration and heat illnesses.
 
Clothing, such as dark, bulky, or rubber protective equipment can drastically increase the chance of heat illness and dehydration.
 
A relative humidity of 35 percent and a temperature of 95 degrees Fahrenheit are likely to cause heat illness, with heat stroke likely.
 
A relative humidity of 70 percent and a temperature of 95 degrees Fahrenheit are very likely to cause heat illness, with heat stroke very likely.