Exercisers Must Adjust to
Summer Heat, Humidity

As summer approaches, people who exercise or play sports outdoors can reduce the risk of heat stroke by giving themselves a chance to adjust to rising temperatures and humidity, according to a sports medicine expert.

"When it gets hot and humid, you see the risk go up," said Dr. William O. Roberts, who is the president-elect of the American College of Sports Medicine (ACSM).

When people who are not accustomed to hot and humid weather exercise outdoors, they run the risk of developing exertional heat stroke, Roberts stated.

Exertional heat stroke differs from traditional heat stroke, which occurs when a person is exposed to extremely high temperatures, such as during a summer heat wave. Victims of traditional heat stroke are often elderly people who do not have air conditioning.

Roberts described traditional heat stroke as "sort of cooking slowly from the outside."

In contrast, exertional heat stroke is caused by activity during hot weather. "You're building body heat from the muscle work you're doing," according to Roberts, who is in the department of family medicine at the University of Minnesota in Minneapolis. "You're cooking quickly from the inside."

Symptoms of exertional heat stroke include muscle cramps, disorientation and exhaustion.

If you start to "feel funny," while exercising outdoors during hot weather, stop exercising and seek out a cool place, according to Roberts.

And if you come across an athlete who has collapsed during hot weather, first rule out a heart attack by checking pulse and breathing, Roberts said. Call 911 and try to cool the person by moving him or her into the shade.

Placing ice or cold soft drink cans on their head and neck may help to cool blood vessels, Roberts said. People who are disoriented should not be allowed to get up, Roberts said. But if a person is lucid, then try to move him or her into an air-conditioned place, he said.

Although exertional heat stroke can occur in dry climates, the risk is greatest during hot and humid weather.

"When it's hot and humid, you can't evaporate your sweat," which helps traps heat in your body, Roberts said.

Anyone who exercises in hot weather can develop exertional heat stroke, but the most at risk are people who are not accustomed to working out in hot weather, according to Roberts.

For instance, people living in a warm climate who work outside all the time gradually get used to rising temperatures and humidity, Roberts explained. The risk of exertional heat stroke increases when temperatures rise in cooler areas, where residents have not yet adjusted to the heat, he said.

The best way to keep from having heat stroke while exercising is to gradually acclimate yourself to warmer weather and to know your "heat tolerance," according to Roberts.

To help your body adjust, Roberts recommended that people gradually expose themselves to warmer weather. For instance, taking an easy walk during the middle of the day may help people get used to the heat, but the morning - when it is cooler outside - may be a better time to go for a run, Roberts said.

Whenever people exercise outside, it is crucial that they drink enough water. Adequate water helps the skin work as a "radiator" to release heat, according to Roberts.

He explained that blood transports heat to the surface of the skin, where it is released in sweat. When people do not drink enough fluids, blood volume declines, which reduces the amount of heat that can be brought to the surface.

Dehydration "keeps your heat transfer system from being as good as it should be."

Drinking too much water, however, has risks of its own. The ACSM recommends drinking enough water to replace fluid lost by sweating. To calculate this amount, the group recommends weighing yourself before and after exercise.

Reference Source 89

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