To acclimate to heat, exercise in heat


September 17, 1991|By Dr. Gabe Mirkin

In 1964, the trial to pick three runners for the U.S. Olympic marathon team was held in 100-degree heat at high noon in Yonkers, N.Y. Buddy Edelin won the race by more than 20 minutes, probably the widest winning margin ever recorded in a major marathon.

How could Edelin run such a fantastic race in such hot weather when he lived and trained in England, where the temperature had been in the 50-degree range for the two months preceding the race? He did it by training in five layers of sweat suits, which made him sweat profusely. The heavy sweating prepared him for hot weather competition.

You can't acclimate to heat just by living in a warm climate. And you can't acclimate to heat just by exercising. To be able to exercise safely in heat, you have to exercise in heat.

When you exercise intensely, your body can generate 20 times as much heat as it does during rest. As you exercise, your heart pumps large amounts of blood from your exercising muscles to your skin, where your sweat glands produce large amounts of sweat to evaporate and cool the blood.

To acclimate to the heat, you need a strong heart to pump a lot of blood to your skin. You have to enlarge the blood vessels in your skin to bring the extra blood near the surface. And you have to enlarge your sweat glands to produce more sweat to evaporate and cool your body.

To do all of these things, you need to train in the heat. In hot weather, spend at least a week exercising very carefully before you try to exercise more vigorously. To be safe, you should ease into hot weather training.


Q: Can strenuous exercise make a man sterile?

A: High scrotal temperature can kill sperm and make a man sterile. But while vigorous exercise raises body temperature, it will not cause sterility.

The body's normal temperature of 98.6 degrees would prevent testicles from making sperm. But scrotal temperature is usually at least one degree cooler. Tight briefs, jeans and jock straps have been implicated as causes of infertility because they hold the testicles closer to the body, thereby raising scrotal temperature.

A high fever can also make a man temporarily sterile. Twenty-five to 55 days after a man develops a high fever, his sperm count becomes markedly reduced and will not return to normal for about 50 days.

In addition, when a man sits for more than 30 minutes in a sauna set at 185 degrees, his sperm count can be reduced, making him sterile.

But that does not happen with exercise. Researchers at Kent State University found that men who exercised hard enough to raise their body temperature as high as 104 degrees -- 45 minutes a day for five straight days -- did not experience a reduction in sperm count, presumably because the high temperature did not last long.


Q: I'm really overweight, but I'm afraid to diet because I know it will slow my metabolism. What should I do?

A: See your doctor for a plan that will combine dieting with exercise.

The most common cause of obesity is a slow metabolic rate inherited from one's parents. That's why some people are thin, even though they eat all day long, and others are fat, even though they eat like birds.

Dieting slows your metabolism even more. The good news is that as soon as you stop dieting, your metabolism will gradually return to its previous rate. The bad news is that to keep from regaining your lost pounds, you will need to exercise and restrict food intake for the rest of your life.

Exercising while you diet will markedly limit the reduction in metabolism. If you exercise when you are not on a diet, you can increase your metabolism above its usual level.

Diets without exercise won't work anyway. If you lose weight successfully solely by restricting food intake, you have less than one chance in 10 of keeping the weight off a year later. You can't spend the rest of your life feeling hungry.

When you start a diet, make sure you also exercise. Otherwise, your metabolism will slow down and you won't continue to lose weight, even though you're eating far less than usual.

Dr. Mirkin is a practicing physician in Silver Spring specializing in sports medicine and nutrition.

United Feature Syndicate

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