According to new research published in the May 16 issue of Journal of the American Medical Association, even small amounts of physical activity, approximately 75 minutes per week (25 minutes, three times per week), can help improve fitness levels for postmenopausal women who are sedentary and overweight or obese.
Low levels of cardiorespiratory fitness are associated with high risk of cardiovascular disease and death, and improvements in fitness are associated with a reduction in these risks. Physical activity habits are the primary determinant of fitness in adults and changes in physical activity result in changes in fitness. Timothy S. Church, MD, MPH, PhD, of the Louisiana State University System, Baton Rouge, La., and colleagues examined the effect of 50 percent, 100 percent, and 150 percent of the NIH Consensus Panel physical activity recommendations on cardiorespiratory fitness in sedentary, overweight or obese postmenopausal women with elevated blood pressure. The Panel recommends at least 30 minutes of moderate-intensity physical activity on most, preferably all, days of the week. The study included 464 sedentary, postmenopausal overweight or obese women whose body mass index ranged from 25.0 to 43.0 and whose systolic blood pressure ranged from 120.0 to 159.9 mm Hg.
Participants were randomly assigned to one of four groups: a nonexercise control group, a 4-kcal/kg (400 calories), an 8-kcal/kg (800 calories) and a 12-kcal/kg (1,200 calories) per week energy-expenditure groups for the 6-month intervention period. Target training intensity was the heart rate associated with 50 percent (a modest intensity) of each woman’s peak VO2 (a measure of oxygen consumption and fitness level).
The average minutes of exercising per week were 72.2 for the 4-kcal/kg, 135.8 for the 8-kcal/kg and 191.7 for the 12-kcal/kg per week exercise groups. Compared with the control group, oxygen consumption increased by 4.2 percent in the 4-kcal/kg, 6.0 percent in the 8-kcal/kg, and 8.2 percent in the 12-kcal/kg per week groups. There were no significant changes in blood pressure values in any of the exercise groups.
“Perhaps the most striking finding of our study is that even activity at the 4-kcal/kg per week level was associated with a significant improvement in fitness compared with women in the nonexercise control group,” the authors write. “This information can be used to support future recommendations and should be encouraging to sedentary adults who find it difficult to find the time for 150 minutes of activity per week, let alone 60 minutes per day.”
In an accompanying editorial, I-Min Lee, MBBS, ScD, of the Brigham and Women’s Hospital and Harvard Medical School, Harvard School of Public Health, Boston, comments on the study concerning physical activity levels and fitness. “… the study by Church et al does provide important information on the dose of physical activity to improve physical fitness, a strong predictor of chronic disease and premature mortality. This may be succinctly summarized for patients and clinicians as ‘Even a little is good; more may be better!’”