The American Heart Association found regular exercise could protect older women from developing an irregular heartbeat.
The researchers found post-menopausal women who were most physically active had a 10 percent lower risk of developing atrial fibrillation (even if they were obese) when compared to women who had low levels of physical activity.
"We found the more physically active the women were, the less likely it was that they would develop atrial fibrillation," said Marco V. Perez, M.D., lead author of the study and independent instructor in cardiovascular medicine and director of the Inherited Arrhythmia Clinic at the Stanford University School of Medicine. "Also, the more obese the women were, the more they benefited from having greater degrees of physical activity."
At the beginning of the study 81,000 post-menopausal women between the ages of 50 and 79 were asked if they spent more than 10 minutes walking per day and how often they participated in high-energy activity that made them sweat.
After an 11 year study period the researchers found the most physically active women (who expended more than nine MET hours per week) had a 10 percent lower risk of developing AF compared to those who didn't walk outside for at least 10 minutes each week. MET is a measurement of how much energy is used during physical activity.
Women who walked briskly for 30 minutes twice a week also reaped some of this benefit. Women who engaged in strenuous activity for more than 15 MET hour per week also had a nine percent lower risk of developing AF. This is the equivalent of running for about two hours each week.
Earlier research suggested strenuous exercise increased AF risk, but "there shouldn't be concerns about these degrees of exercise and AF in older women," Perez said.
The findings were published in the Journal of the American Heart Association (JAHA).
