I'm loving this latest report. According to a new study, even if you've been pretty much a couch potato for most your life, it's not too late. You can still get in shape now in late middle-age and help your heart function as if it were 20 years younger.

The study published in the American Heart Association's journal, Circulation, looked at healthy but sedentary people between the ages of 45 and 64.

Individuals were put into two different groups. The first group participated in a program of non aerobic exercise such as yoga, balance training, and weight training three times a week. The second group, did moderate-to high-intensity aerobic exercise for four or more days a week.

After two years, the group engaging in the higher-intensity exercise saw a dramatic improvement in the function of their hearts.

“We took these 50-year-old hearts and turned the clock back to 30- or 35-year-old hearts,” said Dr. Ben Levine, a sports cardiologist at University of Texas Southwestern Medical Center and director of the Institute for Exercise and Environmental Medicine at Texas Health Presbyterian Hospital. “Their hearts processed oxygen more efficiently and were not less less stiff.”

Sorry, but walking the dog around the block a couple days a week does not seem to do the trick. Of course, any kind of exercise is better than nothing at all, but if you want to turn the clock back on your heart, a bit more is needed. A key part of the effective exercise regimen was interval training – short bursts of high-intensity exercise followed by a few minutes of recovery.

The researchers eased the exercise group into its routine with three, 30-minute, moderate exercise sessions a week for the first three months and built up to a regular set of workouts that peaked at 10 months and included:

* Two days of high-intensity intervals: four minutes at 95 percent of a person's maximum ability (for example, running at a brisk pace or pedaling fast against resistance), followed by three minutes of active recovery (jogging slower, walking briskly, or pedaling slower), repeated four times.

* One day of an hour-long moderate-intensity exercise that raised the heart rate and the participant like enjoyed dancing, tennis, swimming, cycling, or a brisk walk.

* One or two days of 30-minute sessions of moderate-intensity exercise, meaning the participant would break a sweat, be a little short of breath, but still be able to carry on a conversation.

* One or two weekly strength training sessions using weights or exercise machines either on a separate day or after an exercise session.

The participants were encouraged to use diversity with lots of different exercise equipment (stationary bikes, treadmills, elliptical trainers) and engage in outdoor exercises (jogging and cycling) to keep them motivated and interested, Levine said.

The intestinal workout was important, Levine emphasized, even if it was just once a week. Pushing as hard as you can for four minutes stresses the heart, he explained, and forces it to function more efficiently. Repeating the intervals helps strengthen both the heart and the circulatory system.

Another benefit? “It breaks up the monotony of just the walking,” he said. “Most people really enjoy the high intensity work. You would think that they would not but they like the fact that it's short and they like the fact that they feel stronger afterwards.”

The participants tracked their heart rate, which is ideal. But as an alternative, use the simple talk test. During the high-intensity intervals, you should be working hard enough and breathing heavy enough that you can not talk comfortably in long sentences.

Do not wait too long, Levine warned. “The sweet spot in life to get off the couch and start exercising is in late middle-age when the heart still has plasticity,” Levine said. You may not be able to reverse the aging of your heart if you wait until after 70 to begin.

But you'll still see benefits from exercising. A research team at Tufts University found that frail people as old as 89 could tolerate an exercise time that included walking, leg lifts, and stretching. The participants may not have turned back the clock on their hearts, but they improved in ways that could make a big difference. Exercising helped them maintain their mobility and reduced their chances of becoming physically disabled.

“You are never too old, or never too weak, or never too impaired [to benefit from a physical activity program],” said Roger Fielding of Tufts, who led the study published in the Annals of Internal Medicine.

Of course, before starting any strenuous exercise program, be sure and check with your doctor. Then get off that couch and start moving!