Some call it the "either-or" school of exercise: Either you push your body to the higher end of your targeted heart rate range, or the workout is useless.
But now some exercise experts are crying "overkill." Heartbeat ranges have been overemphasized as a barometer of a workout's worth, they say, and less-intensive exercise has plenty of merit for many people.
They are suggesting that target heart rates may have been set too high, especially for unfit beginners, older people and the overweight. What's more, they add, high target ranges can discourage many who are just getting into an exercise regimen and need to start somewhere.
In other words: You don't have to trade your Reeboks for a rocking chair if you're not exercising hard enough to hit the higher end of your targeted range.
Bryant Stamford, an exercise physiologist and director of the Health Promotion and Wellness Center at the University of Louisville in Kentucky, is one who bemoans the idea that exercise must be intense or it's useless.
"This is just not so and tends to discourage participation among many who would benefit from mild exercise," said Stamford, who says that the targeted heart rate concept has been misinterpreted.
That concept, which gauges exercise intensity by measuring a person's heart rate, originated with research in the late 1950s but didn't come into widespread use until a decade later. The idea was to determine your maximum heart rate and then exercise heavily enough to get your rate to a percentage of the maximum.
To estimate your maximum rate, you subtracted your age from 220. Your target range was then 60% to 90% of that number. A 40-year-old's estimated maximum heart rate would be 180, for example, and his/her target range during exercise would be 108-162 beats per minute.
The American College of Sports Medicine currently recommends exercising at a level that produces a heart rate of 60% to 90% of the maximum, but a spokesperson said that guideline is now under review.
Last year, the Aerobics and Fitness Assn. of America, a Sherman Oaks-based organization that trains aerobics instructors, widened its target heart-rate guideline, according to Peg Angsten, vice president of communications.
Instead of 70% to 80% of maximum, the association now recommends 60% to 85%, with 85% intended only for the well-conditioned and 60% to 65% prescribed for beginners, pregnant women and exercisers 60 and older.
Target heart rate is still considered the "gold standard" to measure exercise intensity by most exercise experts. They concede, too, that some well-conditioned enthusiasts love to work out "to the max" and that taking target heart rate is a good idea to guard against overexertion.
But exercising at very high intensity may not be necessary to maintain good health, many exercise physiologists now concur. And, they add, other measurements of exercise intensity may be nearly as legitimate and less confusing than target heart rate, especially for beginners.
"If a beginner focuses on target heart rate, it's going to (make exercise) too difficult and discouraging," said Michael Yessis, a professor of physical education at California State University, Fullerton. "The criteria I'd rather use is, 'Work up a sweat. Get yourself in shape first and then worry about target heart rate.' "
Stamford agreed: "My attitude about target heart rate (for beginners) is to put it on a shelf for at least the first five or six weeks of an exercise program."
Rethinking of the target heart-rate formula was spurred by a number of factors, experts say. One was the realization that few people were following the guidelines.
"Those ranges still work very well in persons (in good physical condition) who want to do them," said William Haskell, a physiologist and associate professor in the division of cardiology at the Stanford University School of Medicine, "(but) a very large percentage of the U.S. population over 45 or surely over 50 were not following those guidelines."
Another factor has been the discovery by several researchers that lower intensity exercise does indeed have benefits.
Said Haskell: "Several (research) groups started looking at, 'What if we train at 60% of maximum heart rate?' "
A number of studies now suggest that training at lower intensities can result in significant aerobic improvement, Haskell said. In one of his studies, he compared three groups of 25 mostly middle-age subjects during a 12-week period: control subjects who did not exercise, subjects who exercised at low intensity (60% of their maximum heart rates) and subjects who exercised at high intensity (75% of their maximum heart rate). The lower intensity group achieved a 10% improvement in aerobic capacity, he said, while the higher intensity group achieved 14% improvement--not a great difference in Haskell's view.
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