Athletes and Hydration

electrolyte replacementAre you wet behind the ears, all wet, or a wet blanket?  Maybe you’re not wet enough.  If that’s the case, you could be in for trouble if you’re an athlete or a wannabe, or even if you’re just working in a hot environment, like the back yard.  The benefits of fluid and electrolyte intake during intense exercise or competition—or grass cutting—are expressed through improved performance and reduced physiological stress on the central nervous, cardiovascular, and muscular systems.  The general theory for staying amply hydrated is well-founded, but the practical recommendations need to be polished.

The goal of fluid management during intense physical activity is to prevent fatigue, illness due to hyperthermia, and both dehydration and overhydration.  Dr. Edward F. Coyle researches factors that limit human exercise performance at the University of Texas at Austin, where he asserted, “When possible, fluid should be ingested at rates that most closely match sweating rate.”  He’s telling us that athletes need to keep their “buckets” full in order to preserve the delicate homeostasis that maintains metabolic equilibrium.  Dr. Coyle defines a hot environment as one that exceeds 30° C (86° F), which may instigate dehydration.  At this point, a loss of “…2% of body weight impairs absolute power production and predisposes individuals to heat injury.”  But he warns that fluid intake must not exceed sweat output to a degree that weight is gained during exercise.  He adds that, “…sodium should be included in fluids consumed during exercise lasting longer than 2 hours or by individuals during any event that stimulated heavy sodium loss (more than 3-4 grams of sodium).”  Optimum benefit is realized by tailoring individual needs to the challenges at hand.  (Coyle. 2004)

At your age, you already know about staying hydrated, but, like most people, you don’t.  You’re afraid that you’ll have to use the head too often if you drink a half ounce of fluid per pound of body weight.  In a couple of weeks, you’ll get used to it, but the volume of water we need is still the subject of torrid debate.  If you’re an athlete, however, things are different.  And if you perform endurance exercises in hot weather, things are vitally different.   Arduous workouts in cold weather, like skiing, put you in the middle.

Loss of 2% of body weight to exercise is getting close to the red zone; 3% will put you there.  Depending on your body size, weight, body mass index, genetics, the weather, your diet and general health, physical condition, the level of the activity at hand, and whatever else you can imagine, you’ll likely sweat half a liter to two liters an hour.  Knowing that one ounce of water weighs one ounce, you can do the math to figure out how much weight that is.  (A liter is 33.8 ounces.)  A professional football or baseball player can lose more than 8 liters of sweat a day.  That’s more than sixteen pounds!  The temp can reach 100° F on a baseball field, by the way.  If you’re a marathoner or a cyclist, sweating about 3.5 liters a day is typical.  Reporting in the Journal of the American College of Nutrition, the US Army Research Institute of Environmental Medicine says to, “…replace fluids frequently when exposed to heat stress, such as one cup (250 ml) every 20 minutes when working in warm environments.”  (Kenefick. 2007)  Don’t dare to tell an endurance athlete he’s not doing any work.

Starting about two to four hours before an event, it’s suggested that you drink fluids at a rate of 5-7 ml per kilogram of body weight, but slowly and not chug-a-lug.  For 7 ml/kg, that equates to ~1 ounce per 10 pounds of weight.  It’s important to include sodium in this routine to stimulate thirst and retain water.  During a marathon, a tennis match, a cycling event, or any endurance contest, aim for a quart of fluid an hour.  Your body will tell you if you have enough, and especially if you’ve had too much.  At the same time, try to eat 1 gram of carbohydrate an hour per kilogram (2.2 pounds) of body weight.  When the competition is over, drink.  You’ll need about 24 ounces of fluid for every pound of weight you have lost.  This is why you have to weight yourself before and after.  But this is as much art as it is science.  Use your intuition to gauge your needs.

All fluids are not created equal.  This is especially true of electrolyte replacement drinks.  Most contain sugar.  While you might think that the carbohydrates in a sports drink are beneficial, think again.  Look at the label.  See how much of the carbohydrate comes from sugar?  More than you thought, right?  The sweet is there to make the drink more palatable.  That means you’re more likely to use it.  But it also makes an acidic environment that inhibits the absorption and metabolism of the electrolyte mineral.  Not good.  Maybe it’s time to step into the adult world and forego the sweets for something that really works.  Besides, sugary sports drinks can erode tooth enamel.  (Meurman. 1990)  (Noble. 2011)  An electrolyte replacement beverage that mirrors the mineral composition of the body is what you want, in as close a ratio as possible.

In sixteen ounces of sweat you’ll lose almost 100 mg of potassium and between 400 and 700 mg of sodium.   Though you can survive on 500 mg of sodium a day, 1500 is a more realistic measure, to guarantee water balance and muscular contraction potential.  If you drink plain water, you most assuredly will dilute your sodium stores and suffer the consequences:  nausea, headache, confusion, loss of energy, restlessness, cramps and spasms, seizures, and coma.  Guess what’s next.

There is a single product on the market that address the electrolyte needs of the endurance athlete with certain efficacy, and that can replace those pediatric drinks you give to the kids when they throw up and get diarrhea from colds and the flu.  Admittedly, it’s an acquired taste, but it’s worth it.  It’s called E-lyte, and is available at Or at   It comes in a regular version and one for endurance athletes, differing by sodium content, since that is the first electrolyte lost to heavy perspiration.  You will perspire a pint a day just by sitting at your desk.  Electrolyte replacement isn’t only for athletes.


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Robert W. Kenefick, PhD and Michael N. Sawka, PhD
Hydration at the Work Site
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Meurman JH, Härkönen M, Näveri H, Koskinen J, Torkko H, Rytömaa I, Järvinen V, Turunen R.
Experimental sports drinks with minimal dental erosion effect.
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Convertino VA, Armstrong LE, Coyle EF, Mack GW, Sawka MN, Senay LC Jr, Sherman WM.
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Gal Dubnov-Raza, Yair Lahavb, and Naama W. Constantinic
Non-nutrients in sports nutrition: Fluids, electrolytes, and ergogenic aids
e-SPEN, the European e-Journal of Clinical Nutrition and Metabolism. 6(4); Aug 2011: pp. e217-e222

*These statements have not been evaluated by the FDA.
These products are not intended to treat, diagnose, cure, or prevent any disease.

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