Keeping your cool while racing against heat barrier

Summertime exercise requires a little care and a lot of water

Health & Fitness

July 11, 2004|By Howard Cohen | Howard Cohen,Knight Ridder / Tribune

Pro boxer Jermain Taylor gets up earlier. Anesthesiologist Philip Zwiebel swaps marathons for triathlons and Ultimate Frisbee devotee Lois Gramley isn't above dousing herself or pals with ice water on the playing field.

Beating the heat smartly. It's critical during these summer months, when working out in the heat and humidity can take a serious toll on your health.

Indeed, more people in the United States died from extreme heat than from hurricanes, lightning, tornadoes, floods and earthquakes combined during a 20-year period ending in 1999, the Centers for Disease Control and Prevention reported. This means that about 175 Americans will die from extreme heat this year with the young, elderly, sick and overweight the most likely victims.

But the heat and humidity doesn't mean one has to grow into a couch potato.

In extreme heat, Zwiebel says while standing outside a South Florida cycling shop, you can still exercise with high intensity if you "do it right."

To do it right, medical experts advise, "Start low and go slow."

When you work out in the heat, your body loses fluids at the rate of a liter every 20 minutes or so. Along with shedding water, you're losing valuable sodium and potassium, electrolytes that keep the body's system functioning properly.

If you fail to replace the fluid, you run the risk of dehydration and, in extreme cases, death.

Swimming is not much different from running or cycling. Though water conducts heat away from the body, you can get dehydrated if you swim at a brisk pace for more than an hour. Keeping a water bottle at pool's edge is wise.

Humidity is crucial

Eyeing only the thermometer is also foolhardy. Places like Las Vegas, Texas and Arizona, for instance, soar over 100 degrees but may actually be safer than places that are cooler but have higher humidity.

Dr. Andrew Sherman, a physiatrist specializing in musculoskeletal medicine and assistant professor of rehabilitation medicine at the University of Miami, says: "When you sweat, it evaporates off, and that's how the body cools. ... When you have humidity around 80 to 90 percent, you sweat and it just stays there on your body. ... It's not evaporating, and so your core heat is increasing. The risk of dehydration and heat exhaustion is much higher."

This means you need to pay more attention to hydrating and avoiding midday workouts, when the temperature and humidity are extreme.

If the temperature reads 90 degrees, for example, and the humidity is 80 percent, the "apparent" temperature is 113 degrees. Your body reacts to this elevated temperature. In a place like Las Vegas, with a 90-degree reading and 20 percent humidity, the apparent temperature dips to 87.

Water is the best coolant for physical activities lasting under an hour, experts say. Sports drinks are good for those engaged in longer activities such as long-distance runs or bike rides, because they replace lost electrolytes.

Gradual approach

Thawing out after winter's hibernation can also lead to problems. "Whenever one goes from a relative or absolute period of inactivity, people usually don't use the common sense necessary to realize they can't go immediately back to what they did before. The activity has to be gradual because the cardiovascular system ... doesn't do as well with sudden exertions," says Dr. Stephen Glasser, a professor of epidemiology at the University of Minnesota.

Ironically, the risk of heart attack is greatest in the morning, a time of day experts recommend for outdoor activities. Working out on the weekends, after a Friday night of imbibing, adds to the risk of dehydration. Alcohol, as well as caffeine, is a diuretic.

"The caveat is, it's better to exercise at any time of day than not at all," Glasser said. "We don't want to scare people from working out or working out in the morning, but each person should evaluate their particular risk."

So Jermain Taylor, the 25-year-old boxer from Miami, wears looser clothes, hydrates and starts his workout at 6 a.m. in the summer. "In the winter I get up later. I wait for the sun to come up."

Lois Gramley, a 30-ish registered nurse who chases the Frisbee or runs regularly, starts swigging water and diluted Gatorade before working out.

"We compete in tournaments that last all day, so you don't want to start out dehydrated," she says. "I prefer to workout outdoors, all [drenched] in perspiration. We rehydrate and keep going."

Hot tips

Summer workout advice:

* Drink fluids -- at least 16 ounces -- and drink 12 to 16 ounces an hour or two before working out.

* Water is best for activities lasting 30 minutes or less. For longer, more intense sessions, consume drinks that replace lost sodium and potassium. Dilute sports drinks with water to cut down on sugar.

* Wear lightweight, light-colored and loose-fitting clothes. Don't forget a hat.

* Use a strong sunscreen and reapply often.

* Avoid midday exercising; work out before 10 a.m. or after 4 p.m.

* Find a neighborhood with tree canopies and run under them.

* Route your run so that you can take a pit stop in an air-conditioned area. "The benefits of running won't be diminished if you stop for five minutes; in terms of getting your body temperature down, it could be a major save," says anesthesiologist Philip Zwiebel.

* Run or cycle away from the wind initially so when you finish you'll head back into the wind and feel cooler.

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