HIKE, DRINK AND BE MERRY: Winning the Battle Against Dehydration
The ARS Sojourner
Inadequate fluid intake can cause or worsen dehydration, heat stroke, hypothermia, and altitude sickness.
How much liquid should be consumed while exercising outdoors? The American College of Sports Medicine offers three guidelines for athletes:
1. Consume adequate fluids for 24 hours before exertion. (Don't start with a fluid debt.)
2. Drink about 500 mL (17 oz.) in the two hours preceding an activity. (Load up with liquids while traveling to the starting point.)
3. Drink 600 to 1,200 mL/hour while involved in strenuous activities. (This is about 20 to 40 ounces per hour! Sometimes even more water consumption is helpful. The military found that enforced drinking of large amounts of water prevented heat injury during extreme conditions of desert warfare. Up to 6 Liters/hour were needed).
Generally the best fluid to drink is water, but the addition of electrolyte (salt) and/or carbohydrate (sugars) may be useful.
Salt helps the intestine absorb liquids faster and replaces the sodium lost in sweat. From 0.5 to 0.7 grams per Liter is the recommended amount to add.
A level teaspoon of salt weighs about 7 grams. Addition of 1/10 of a teaspoon of salt to a quart of water will do the job - not more than a pinch! If too much salt is taken the body is forced to excrete extra water to get rid of it. Salt tablets are no longer recommended.
Sugars can provide a source of quick energy that may delay fatigue. They also make fluids easier to drink by improving taste. I find that a small amount of punch powder in my canteen takes away the stale taste and increases my water consumption.
Commercial sports drinks are expensive, but they usually contain appropriate amounts of carbohydrate and electrolyte. In hot weather it is better to choose an electrolyte-rich drink. In cold weather, drinks with more carbohydrate are appropriate.
Proper clothing will help avoid dehydration and heat injury. In the desert, loose garments that cover the entire body will help prevent rapid evaporation of sweat and excessive water loss. In a jungle-like environment with high humidity, covering the skin may not allow sweat to evaporate quickly enough to cool the body.
In each case, the key to prevention of injury is adequate drinking.
An easy way to estimate the body's level of hydration is to look at the urine. Pale urine (the color of dilute lemonade) means the body is well hydrated. Dark urine means that more water consumption is needed.
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Dr. Bob Armstrong, N7XJ, is an avid outdoorsman, QRPer and practicing physician living in Manti, UT.