DURHAM, NC–How much you exercise may be more important than a workout’s intensity when it comes to improving cardiovascular health, according to new research.

Researchers at Duke University Medical Center looked at sedentary overweight men and women and found that a moderate exercise regimen can provide significant improvements in fitness levels while reducing the risks of developing cardiovascular disease. The results of the analysis were published in the October 2005, issue of the journal Chest.

"People only need to walk up to 12 miles per week or for about 125 to 200 minutes per week to improve their heart health," said the lead author Brian Duscha. "Our data suggest that if you walk briskly for 12 miles per week you will significantly increase your cardiovascular fitness levels compared to baseline. If you increase either your mileage or intensity, by going up an incline or jogging, you will achieve even greater gains."

Good news for health club owners courting the deconditioned population -- the researchers said their findings should inspire couch potatoes who have been hesitant to begin exercising regularly, especially since earlier analysis of the same participants by the same Duke team found that people who do not exercise and maintain the same diet will gain up to four pounds each year.

"The participants in our study received the fitness benefits without losing any weight," Duscha said. "Many people exercise to lose weight, and when that doesn't occur, they stop exercising. However, the truth is that you can improve cardiovascular fitness and reduce the risk of heart disease by exercising without losing weight."

Researchers studied 133 overweight sedentary men and women who were beginning to show signs of blood lipid levels high enough to affect their health. They were randomized into one of four groups: no exercise, low amount/moderate intensity (equivalent of 12 miles of walking per week), low amount/vigorous intensity (12 miles of jogging per week) or high amount/vigorous intensity (20 miles of jogging per week).

Since the trial was designed solely to better understand the role of exercise, patients were told not to alter their diet during the course of the trial, which lasted six months for the group that did not exercise or eight-months for the exercise groups. The additional two months for the exercise group came at the beginning of trial, when participants slowly ramped up their exercise to their designated levels. The exercise was carried out on treadmills.

For their analysis, the team compared peak VO2 and time to exhaustion (TTE) – before and after the trial. While all the exercise groups saw improvements in both measurements after completing their exercise regimens, the researchers noticed some interesting trends.

"We found that when we compared the low amount/moderate intensity group to the low amount/vigorous intensity group, we did not see a significant improvement in peak oxygen consumption," Duscha said. "However, when we increased the amount of exercise from 12 to 20 miles – at the same intensity – we did see an improvement in peak oxygen consumption."

Also, although no statistically significant difference was detected between the low amount/moderate intensity group and the low amount/high intensity group, the researchers did see a trend toward both a separate and combined effect of exercise intensity and amount on increased peak VO2 levels.