TUESDAY, May 15 (HealthDay News) -- A new study has good news for those who've been avoiding exercise because they don't think they have enough time: Even 10 minutes a day can improve your cardiovascular fitness.

The research found that when overweight or obese, sedentary women started to exercise an average of 72 minutes a week, they increased their peak oxygen consumption -- a measure of cardiovascular fitness -- by 4.2 percent compared to women who stayed on the sidelines.

"For people who've been really sedentary, you're getting a benefit almost immediately. Just get off the couch," advised the study's lead author, Dr. Timothy Church, director of the Laboratory of Preventive Medicine Research at the Pennington Biomedical Research Center at Louisiana State University.

"It was surprising to us, the idea that as little as 10 to 15 minutes of exercise a day could provide benefit in terms of fitness," he added.

The researchers also found that while a little bit of exercise was beneficial, more exercise boosted cardiorespiratory fitness even higher.

Church noted that the intensity of exercise the women in the study engaged in was very low, probably equivalent to walking at a speed of about 2 to 3 miles an hour.

The findings are published in the May 16 issue of the Journal of the American Medical Association.

"Physical activity is clearly beneficial for your health. This study shows that any activity is good, and more is better," said Dr. I-Min Lee, an associate professor of medicine at Brigham and Women's Hospital and Harvard Medical School, both in Boston. Lee wrote an accompanying editorial in the same issue of the journal.

Church and his colleagues undertook the research, because there have been few studies that have looked at the dose-response effect of exercise -- that is, how much exercise do you need to see a benefit and will more exercise continue to produce additional benefits?

To answer those questions, the researchers recruited 464 postmenopausal women who were considered overweight or obese. All of the women had some degree of high blood pressure, and none was exercising at all at the start of the study.

The women were randomly assigned to one of four groups: the control group that would remain sedentary; a light exercise group that averaged 72 minutes a week of exercise; a moderate exercise group that averaged about 136 minutes a week; and a high exercise group that completed nearly 192 minutes of exercise each week.

Current recommendations call for 30 minutes of exercise most days of the week. Church said the three exercise groups roughly translate to 50 percent, 100 percent and 150 percent of the exercise guideline.

The researchers measured the women's peak oxygen consumption at the start of the study, and then again after six months of exercise. They found that the women in the light exercise group increased their peak oxygen consumption levels by 4.2 percent. The moderate exercise group saw a 6 percent rise, while the heavy exercise group upped their cardiorespiratory fitness by 8.2 percent.

"This is great news for couch potatoes and for the aging," said Church. "There are people that can't obtain the recommendations for exercise, but now, we see if you can't get 150 minutes a week, you stand to benefit even if you get half that."

Lee said: "These findings suggest that different outcomes may show different responses. Even with a little bit of physical activity, there was a significant improvement in physical fitness. And, this study showed that as the dose increased, you saw commensurate increases in fitness.

"With a very doable dose of physical activity, you can start seeing health benefits," Lee added.

More information

To learn more about the benefits of exercise, visit the American Academy of Family Physicians.

SOURCES: Timothy Church, M.D., M.P.H., Ph.D., director, Laboratory of Preventive Research, Pennington Biomedical Research Center, Louisiana State University, Baton Rouge; I-Min Lee, M.B.B.S., Sc.D., associate professor of medicine, Brigham and Women's Hospital and Harvard Medical School, and associate professor of epidemiology, Harvard School of Public Health, Boston; May 16, 2007, Journal of the American Medical Association