For older exercisers, effort counts.

At least that's what a large Harvard study of heart disease in older men showed.

It found that those who thought their workouts were hard had a lower risk of coronary heart disease, even though the amount of energy they burned was below minimum federal guidelines.

"Are they getting any benefit? The bottom line is yes, they are," said researcher I-Min Lee of the Harvard School of Public Health. Even though the study involved only men, Lee said the study could be applied to women as well.

The study suggests that older people may be able to do less exercise and get heart health benefits -- provided they feel they are working hard. The findings were published in February in the American Heart Association journal Circulation.

The health benefits of exercise classes are what keep Velda Witt and Ruth Irwin coming back to Universal Health and Fitness Center in Cape Girardeau.

The two women said they enjoy the Active Us class for adults over age 55.

"I feel better and just enjoy it," said Witt, who drives from Chaffee, Mo., twice a week for the hourlong class. She also uses some of the machines in the workout center to help combat osteoporosis.

The Active Us class works every muscle group and really helps people to lower their cholesterol and blood pressure, said Jane Greening, who teaches at both Universal and Main Street Fitness in Jackson.

"I gear the workout to the higher levels, but everything can be modified," she said.

The class is part of a series geared for people over age 55.

Main Street Fitness also urges senior adults to try some exercise classes especially for them. The classes "give them a good, safe workout and proper instruction," said Scott Givens, assistant manager of the fitness and wellness center.

But people are also encouraged to "mingle in at their leisure" if there is a class that interests them, he said. "We tell them to just modify that."

Givens thinks more older adults are aware of the benefits of exercise and are exercising more.

Irwin said exercising gives her plenty of energy for the rest of the day. She's been coming to the aerobics classes for about five weeks, so her endurance has improved over time.

The class also has helped strengthen her back after a surgery, she said.

Much of the exercises are part of a low-impact routine, so that older adults can exercise without feeling too much strain on their body. Everyone comes in with a differing level of activity, and Greening explains to newcomers how some exercises can be adapted for those levels.

"Being in a group sort of motivates them to work a little harder," she said. "They try to keep up with the Joneses."

If a person's fitness level is low at the start, then a strong effort can create a training effect, said scientist William Haskell of Stanford University, who was not part of the research team. Training that feels hard can be enough to increase the heart's ability to pump more blood with each beat, and also could reduce cholesterol levels, he said.

Lee said she did the study to see if people who do less than the targeted MET, or resting metabolic rates, in the study would still get some benefit. A resting metabolic rate is the amount of energy a person uses to sit quietly.

However, neither Lee nor Haskell believe people should try to get by on less. For one thing, a higher metabolic rate means more calories are burned -- and weight can be lost.

But current MET standards don't adequately account for the slowing of metabolism that comes with age, Lee said. The guidelines are based on the bodies of younger adults who have higher metabolic rates that could run at 3 to 6 METs in moderate exercise, she said.

Lee said older people would feel they are working just as hard at lower METs.

Although the science behind the exercise recommendations is based in part on METs, the guidelines themselves are written in language based on ratings of perceived exertion. Because people can't keep track of their METs, the guidelines call for at least moderate exercise for a minimum of 30 minutes on most days of the week.

Lee would not change the wording. The recommendations are easy to understand and widely applicable -- and even older exercisers who won't reach 3 to 6 METs still could find their efforts rewarded, she said.

Features editor Laura Johnston contributed to this report.