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The Truth About Heart Rate and Exercise

Do you really need to track your heart rate when you work out? Experts weigh in.

3. TRUE OR FALSE: Maximum heart rate declines with age.

TRUE. As we all know, exertion makes the heart beat faster, and the greater the exertion, the faster the heart rate. But there's an upper limit on how fast your heart can beat, and that limit is affected by age.

"Maximum heart rate is unrelated to exercise training," Hirofumi Tanaka, PhD, tells WebMD. He's an associate professor of kinesiology and health education at the University of Texas and director of the university's Cardiovascular Aging Research Laboratory.

"Whether you're a couch potato or a highly trained athlete, that rate declines about seven beats per minute for each decade," Tanaka says. Regular exercise can lower your resting heart rate, but it does nothing to slow the age-related decline in maximum heart rate.

4. TRUE OR FALSE: Moderate exercise promotes weight loss more effectively than vigorous exercise.

FALSE.  Weight loss is a matter of simple arithmetic: To shed pounds, you must burn more calories than you consume. And when it comes to burning calories, the greater the exertion, the greater the rate at which calories are burned.

Working out at about 60% to 75% of your maximum heart rate (the so-called "fat-burning zone") burns fewer calories than working out at 75% to 85% of your maximum heart rate (the so-called "aerobic" or "cardio" zone).  

But caloric burn depends on a workout's duration as well as its intensity -- and it's easier to work out longer when exercising at a lower intensity.

5. TRUE OR FALSE: There's a simple and reliable formula for calculating your maximum heart rate.

TRUE. There is such a formula -- but there are two big caveats.

For starters, it's not the familiar 220 minus your age in years. That formula, first promulgated in the 1960s, works reasonably well for people under age 40. But it overstates the maximum heart rate for older people.

A more accurate formula is the one published in 2001 by Tanaka in the Journal of the American College of Cardiology: Multiply your age by 0.7 and subtract that figure from 208. For example, a 40-year-old has a maximum heart rate of 180 (208 - 0.7 x 40).

Formulas aside, maximum heart rates vary, even among people of the same age. "The formula is only relevant for groups of people," Levine says. "For individuals, the prediction is off by plus or minus 10 to 20 beats per minute."

It's possible, of course, to determine your maximum heart rate by running or riding a bike to the point of exhaustion. But because it can be risky, exercising that intensely is not recommended for men over 45 or women over 55, as well as for heart disease patients or people with heart disease risk factors, unless they have been exercising regularly or have been cleared to exercise by their doctors.

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