Performance can be directly affected by dehydration, therefore the importance of adequate hydration cannot be overemphasized.
If urine is not lightly colored to clear, you are probably dehydrated. Urinating every 2 to 4 hours is normal. If urinating more frequently than every 30-60 minutes you’re drinking too much. One liter of sweat lost = 2.2 pounds. The body needs .3 x its weight in fluid for the minimum number of ounces you require daily (eg: .3 x 150 lbs. = 45 fl. oz. or 5.25 8 oz. glasses of water). This does not include loss due to exercise.
Rehydration should be completed within 2 hours post exercise.
Fruit juices, carbohydrate gels and carbohydrate drinks containing concentrations > 8 % are not recommended during exercise. Beverages with > 8% carbohydrate concentrations require greater digestion, thereby slowing gastric emptying and delaying water getting absorbed into the body’s tissues. These types of carbohydrate drinks should be consumed at least 30 min. prior to competition. Athletes in sports with extended time between periods of intense exercise would find these drinks beneficial but should be cognizant of allowing enough time between periods of exercise for them to be digested. They are not a substitute for proper nutrition (meals) and adequate water replenishment. Read the product labels to find out how much carbohydrate is in the drink. For example, if one serving of the drink is 200 calories and also contains 40 g of carbohydrate per serving, multiply 40 g x 4 calories (1 gram of carbohydrate = 4 calories) which = 160 calories of carbohydrate. .08 x 200 c = 16 c, 160 > 16, therefore, this drink is > 8% concentration, is too high in carbohydrates and should be avoided during exercise of short duration but may be used for long competitions.
Long Competitions > 2 hours in length: Competitions lasting longer than 2 hours may require a little extra carbohydrate during the competition. Examples of this type of competition would be: marathon, iron man competition, mountain climbing, hiking, and day long bike rides, or any ultra endurance sport. For these types of events, 1 cup or 8 oz. of a sports drink containing 6-10% carbohydrate concentration every 15-20 minutes can delay the onset of fatigue by maintaining hydration and providing carbohydrate for energy via carbohydrate metabolism. This equates to 24-30 grams every half hour.
Contests that may last all day but in which the athlete is not competing the entire time are not included as competitions > 2 hours and generally do not need extra carbohydrate at intervals throughout the day. Athletes in these types of competitions may ingest small meals or snacks as necessary throughout the day. Examples of all day competitions but which do not fall into the category of long competitions would be: track meets, volleyball matches, swim meets, fencing meets, tennis matches, sailing races, sports play days, and golfing.
The effects of dehydration include fatigue, thirst, irritability, general discomfort, headache, weakness, dizziness, vomiting, head or neck heat sensations, nausea, chills, cramping, extremely dry mouth, lips and/or throat, high heart rate, clammy skin or dry skin crusted with dried sweat and a decrease in performance.
If you know you sweat profusely with exercise, get in the habit of weighing yourself before and after exercise. For every pound of weight you have lost through perspiration drink 2 cups (1 pint or 16 oz.) of water.
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Last updated 12/8/2005 by MIT Sports Medicine: K. Davis
Copyright 2005 by MIT