Posted 05/15/2007

Study reveals even small amounts of physical activity
 improve fitness levels for many women

"Any type of moderate intensity physical activity should provide comparable benefits to those seen in our study. The women in this study walked on treadmills and rode stationary cycles, but any activity of comparable energy expenditure would produce similar results."                                Dr. Steven Blair

Even small amounts of physical activity - as little as 75 minutes a week - can improve heart and respiratory fitness levels for many women, according to a study in the May 16 issue of the Journal of the American Medical Association.

Dr. Steven Blair, one of the study’s authors and a professor at the University of South Carolina Arnold School of Public Health, said 15 minutes of physical activity five days a week will yield important health benefits for postmenopausal women who are sedentary and overweight or obese.

"Thirty minutes of moderate-intensity activity, such as walking, on at least five days is the the fundamental public-health recommendation," he said. "We have a great deal of data from many studies that this dose of activity provides extensive health benefits. In addition, getting 45 minutes a day provides even more physiological adaptation and greater health benefits."

The study’s results should be encouraging to sedentary adults who find it difficult to find the time for 150 minutes of activity per week, let alone 45 to 60 minutes per day, he said.

The study, conducted between 2001 and 2006, included 464 sedentary, postmenopausal overweight or obese women, who also had high blood pressure.

Participants were randomly assigned to one of four groups: 102 to the non-exercise control group; 155 to the group that expended 400 calories per week through physical activity; 104 to the 800-calorie group; and 103 to the 1,200 calorie group. They were monitored for six months.

The researchers’ most striking finding: Even activity that burned only 400 calories - approximately 72 minutes over about three days - resulted in a significant improvement in fitness compared with women in the non-exercise control group, said Blair, who collaborated on the study with researchers from Louisiana State University and Indiana University.

"Any type of moderate intensity physical activity should provide comparable benefits to those seen in our study," he said. "The women in this study walked on treadmills and rode stationary cycles, but any activity of comparable energy expenditure would produce similar results.

"And that’s good news. This can include work around the house and yard, swimming, playing in the park with your grandchildren, or other activities that are of a similar intensity to brisk walking."

The women in the study trained at only about 50 percent of their maximal capacity for physical activity.

"This is not very strenuous," Blair said. "This level of exercise will produce an increase in breathing and heart rate but will not leave you breathless or exhausted."

Low levels of cardiorespiratory fitness are associated with a high risk of cardiovascular disease and death.

"This study provides more information for our understanding of the amount of physical activity needed to improve fitness and health among people," Blair said. "We must continue to identify and refine efficient, safe and acceptable exercise prescriptions to improve fitness. This is of substantial public health importance."