Unfit people should be wary of sudden exertion


January 04, 1994|By Dr.Gabe Mirkin | Dr.Gabe Mirkin,Contributing Writer/ United Features Syndicate

Two recent studies in the New England Journal of Medicine show that if you're out of shape, you shouldn't immediately begin to exercise vigorously (Dec. 2, 1993). People who exercise less than once a week are 100 times more likely to develop a heart attack during a sudden burst of physical activity.

Exercise markedly increases your heart's needs for oxygen. Oxygen is brought to your heart through arteries on its outside surface. Many out-of-shape people have fatty plaques blocking these arteries, so when they try to exercise vigorously, their heart can't get the extra oxygen it needs and starts to beat irregularly. Part of the heart muscle dies, and the person suffers a heart attack.

There are lots of situations that can tempt you to exert yourself. You could be drawn into a basketball game with your kids, or you might decide to ski or swim while on vacation. You can even inadvertently overdo while lifting a heavy package, trying to catch a plane or attempting to chop wood. Any of these sudden bursts of exercise can cause a heart attack when you are out of shape.

If you smoke, have high blood cholesterol or blood pressure, chest pains or a family history of heart attacks, you are at even greater risk of developing a heart attack with a sudden burst of exercise. If you don't exercise regularly, check with your doctor and start a gradual, controlled, three-times-a-week program of walking, cycling, dancing, jogging or swimming. You can then become fit enough to withstand sudden exertion without harm.

Q: Does menstruation affect athletic performance?

A: There is no evidence that menstruation interferes with a woman's strength, speed, coordination or endurance or that her rates of taking in and using oxygen and sweating change. A survey done at the 1972 Olympic games showed that more than 70 percent of the female athletes felt that menstruation has absolutely no effect on performance.

Some women feel irritable just before they start to menstruate. This may affect coordination, which is primarily a mental function and depends on how the brain regulates the more than 500 muscles in the body. Studies done in England show that women may have slower reaction times during menstruation. Nobody really knows the cause of premenstrual symptoms.

The vast majority of female competitive athletes do not need to manipulate their menstrual cycles to enhance performance. However, some women feel that they can compete at a higher level when they are not menstruating.

Elite athletes who feel this way can ask their doctors to manipulate their periods for major competitions. These women can take conventional birth control pills for several months prior to their championship events and then stop taking the pills 10 days before their competition. They will usually start menstruating within 3 days and stop menstruating before they compete. An alternate method is to take progesterone, such as 5 milligrams of medroxyprogesterone acetate, for 10 days, from 10 to 20 days before competition.

Q: Is there any special benefit to sports drinks made with fructose?

A: If you pay extra for drinks that contain fructose, you're wasting your money, unless you are a diabetic. If you are diabetic, fructose can help to control your weight.

When nondiabetics eat table sugar, their bodies produce a lot of heat and use up calories.

When diabetics eat table sugar, they do not use the calories, so it is more fattening to them. However, fructose is not more fattening to diabetics, as it produces a normal amount of heat.

If you are not diabetic, fructose offers no health advantages over regular sugar (sucrose), costs 14 times as much and often causes diarrhea when taken in large amounts.

Fructose is a single sugar. Sucrose, or table sugar, contains fructose bound to glucose to form a double sugar molecule.

When you eat glucose, it is immediately broken down into the single sugars, fructose and glucose, and you absorb each.

However, fructose cannot be absorbed effectively when glucose not also present.

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

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