Comfort is key to ideal heart rate


A lot of people use pulse rate monitors when they exercise, but you don't need one. The only exercise pulse rate that you need to know is your training pulse rate, a mythical number that will strengthen your heart without causing pain. You don't have to know the number of beats per minute because you reach your training pulse rate when you just start to require more oxygen. You will just start to breathe more frequently and more deeply, causing you to raise your shoulders as you take deeper breaths.

To determine your training rate, many fitness instructors use the formula: 60 percent of your maximum heart rate. The fastest your heart can beat is calculated as 220 minus your age. This is an arbitrary measure because your maximum heart rate is determined by how strong your skeletal muscles are and does not measure the strength of your heart muscle. The stronger your skeletal muscles, the harder you can use them and the faster your heart will beat.

As you age, your skeletal muscles weaken and your maximum heart rate drops. A 50-year-old will have a maximal heart rate of 220 minus 50, which is 170, and his training formula heart rate is 60 percent of 170, which is 102. A 70-year-old has a training pulse rate of 60 percent of his maximum heart rate, which is 220 minus 70 or 150. That times 60 percent equals 90 beats a minute.

You do not need a pulse monitor. Just start off slowly, and gradually increase your pace until you just start to raise your shoulders and breathe faster to take in more air. Try to hold that pace. You should still be able to talk. If you feel uncomfortable, slow down.

Q: I hear rumors about professional athletes using cocaine. Can you help me explain what's going on to my teen-age kids?

A: When you hear about an athlete dying suddenly and the autopsy reports that he had a heart attack with multiple dead areas in the heart and dilated cardiomyopathy, think of cocaine.

Many top athletes take cocaine because they think that it improves their game. In 1884, Sigmund Freud, the father of psychiatry, showed that within minutes of snorting cocaine, a person can contract his muscles with more force and react faster to external stimuli. For example, a basketball player can dribble around an opponent and respond faster to moves to block him.

Cocaine is a potent stimulant that makes an athlete more alert. It makes him feel that he can accomplish more and makes him willing to suffer more. A basketball player on cocaine may attempt to take shots farther out from the basket than he usually does. These effects can last up to three hours.

A study published in the March 1994 issue of the International Journal of Cardiology shows that exercising after taking cocaine markedly increases a person's chances of developing irregular heartbeats and dying.

Cocaine is a potent stimulant that makes your heart beat faster. Low doses of cocaine usually do not cause significant irregular heart beats, while higher doses often do. This study shows that a low dose of cocaine can cause irregular heart beats during exercise. Cocaine augments the effects of the body's own natural stimulants epinephrine and norepinephrine, which raise blood pressure and makes the heart beat faster, stronger and more irregularly.

Q: I've been lifting weights for about six months, and several of the guys at the gym say I should eat lots of meat to get more iron. I'm already taking iron pills. Can you get too much iron?

A: Several recent papers have shown that high blood levels of iron are associated with an increased risk of suffering heart attacks and cancers, particularly those of the esophagus and bladder. A recent study from Harvard shows that it may be the meat , rather than the iron itself, that causes the heart attacks and cancers. The data clearly show that eating meat and chicken increases your chances of developing heart attacks and cancers. People who eat a lot of meat, fish and chicken have higher blood levels of iron than vegetarians. The iron in meat, fish and chicken is called heme iron, which is absorbed at a very high level, 10 percent to 20 percent. The iron that you get from plants is absorbed very poorly -- 1 to 3 percent of the iron in the food that you eat.

So, even though there is an association between high iron levels and cancer and heart attacks, we do not know if the iron causes these diseases. You can find out if your iron level is too high by asking your doctor to draw blood for a test called transferrin iron binding saturation. People with a transferrin iron binding saturation of more than 60 percent are at increased risk for developing heart attacks and cancers. If your level is greater than 60 percent, you can reduce your intake of iron by restricting intake of meat and iron-supplemented foods, and you can get rid of extra iron by donating blood six or more times a year.

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

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