Perspiring depletes your body of needed fluid and nutrients, so stay hydrated

Credit: Michael Cooper/Allsport
The sun beat down mercilessly on Frank Fedel's head as he churned forward in the Ironman Triathalon last summer. Sweat poured as he ran five, then six miles in the 85-degree heat, trying to catch up with a friend, never stopping to swig water.

Then he bonked. He felt woozy, tipsy, ready to vomit. His muscles cramped up.

Fedel, 45, took almost an hour to walk a mile back to the medical tent, where he downed eight glasses of water and two bottles of potassium-rich sports drink before resuming the race.

"During vigorous exercise, your body can sweat out 2 liters of water in just an hour. If you don't replace the fluids fast you can collapse from heat stroke," says Fedel, a Royal Oak-based exercise physiologist who trains candidates for extreme sporting events.

Perspiration, or sweating, is the body's way of dealing with heat. When you exercise, mow the lawn, stand in a line at an amusement park or do anything else that makes you hot, some or all of your 2 million to 4 million sweat glands secrete water along with small amounts of sodium and potassium. As the sweat evaporates, your skin is cooled, helping to maintain a constant body temperature.

If you sweat a lot without replenishing your internal water supply as Fedel did you deplete the most important nutrient in your body. Water makes up 70 percent of your muscles and 75 percent of your brain.

"At 1 to 2 percent dehydration, you hurt your athletic performance; at 6 to 7 percent loss, you keel over. People die from dehydration," warns Nancy Clark, spokesperson for the American College of Sports Medicine. "Unless the water loss from sweat is replaced, the blood gets thicker and thicker, making it harder for the body to function. It can't transport oxygen to the muscles."

Under duress, hormones tell the kidneys to conserve water by urinating less, so the urine you pass is amber-colored like beer, instead of light-tinted like lemonade.

Bob Goebel of Shelby Township, who rides a tandem bike on long-distance rides with his wife, Rose, learned that firsthand. During a ride, she warned him he was sweating excessively and swaying more than usual. He didn't grasp the seriousness of his condition until he relieved himself and noticed his urine was dark. He doused his head in water, drank several bottles of water and took a short nap in the shade before proceeding.

Failure to react can be fatal. In 1997, University of Michigan wrestler Jeffrey Reese collapsed and died after working out for two hours in a 92-degree room while wearing a rubber suit. He was trying to lose weight for a match the next day.

His death along with the deaths of two other wrestlers in 1997 led the NCAA to outlaw radical weight-loss methods and implement rules, including one that requires athletes to be properly hydrated to compete.

"If your goal is weight control, exercising at higher intensity levels to stimulate perspiration won't burn more fat than exercising for a longer period at a more moderate pace," says Marty Lilistone, a nutritionist for Beaumont Hospital who monitors its weight-loss program.

Though it's only human to notice the guy next to you has drenched his shirt before you've sweated a drop, don't use such comparisons to determine whether you're on the verge of dehydration.

Sweat patterns are inherited, says Dr. Tor Shwayder, director of pediatric dermatology at Henry Ford Hospital.

To determine if you're getting dehydrated, focus on how you're feeling. If your throat is parched, your lips are dry or every step feels labored, consider this a warning to cool down and take in some fluids. If you feel woozy, eat a piece of fruit or have a sport drink.

Veteran sailors in the Bacardi Bayview Mackinac Race take a jump in the lake when they start overheating.

"Lake Huron is about 60 degrees in the summer. It will cool you off quickly," says John Barbour, a 33-year participant.

To avoid dehydration, Fedel sets a timer on his watch for 15 minutes; it beeps to remind him to drink water.

"It's better to (urinate) a lot than bonk out," Fedel says. "No one ever died from having to urinate, but plenty of people risk serious injury from not drinking water while they exercise."

Those who fail to drink enough may stop sweating, a sign of heat stroke. Headache, numbness, confusion and rapid pulse are also signs the body can't deal with heat buildup. In advanced stages of heat stroke, you may need an ice bath or intravenous fluids to cool down.

If you want to know how much water to drink so you replenish yourself without taking on water weight, Lilistone recommends this exercise: Weigh yourself naked before and after exercise. If you lost 2 pounds, you have lost 32 ounces or a quart of sweat. You have to replace that much just to stay even. A healthy body eliminates the equivalent of eight glasses of water a day.

"Drink as much water as you can stand before a race; drink until you have water in your mouth you can't stand to swallow," Fedel says.

People who drink coffee and caffeinated beverages regularly along with exercising tend to have bodies that adapt. But even sailors have learned that what the body can stand isn't necessarily what's best for it.

"Since the advent of cheap bottled water, we've found numerous sailors have switched from beer to water while racing their boats," Barbour says. "They find they perform better, feel more in control while drinking water. They save the beer and Bacardi to celebrate after the race."

They've learned from experience, so remaining hydrated is no sweat.

Next time: Warning signs and solutions for dehydration

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