Strenuous daily exercise may actually raise risk for heart disease, stroke and blood clots, while moderate physical activity a few times a week lowers it substantially, according to a new study of 1.1 million women published in Circulation.
Not only did the study pinpoint exactly how hard and how often women should work out to get the best protection against their leading health threat–cardiovascular disease (CVD)–but the researchers also reported that as little as one hour a week of moderate activity had surprisingly powerful benefits.
“These findings may offer some hope–and perhaps even a dash of inspiration–to the estimated 30 percent of adults worldwide who struggle to achieve the recommended levels of physical activity,” Rachel R. Huxley, MA, DPhil wrote in an accompanying editorial, “Physical Activity: Can There Be Too Much of a Good Thing?”
What’s the Optimum Amount of Exercise?
The researchers tracked initially healthy women (average age 56) for nine years, and compared their cardiovascular outcomes with their self-reported frequency and intensity of physical activity. Among the key findings were the following:
- For strenuous exercise (enough to cause sweating or a faster heart rate) the optimum frequency was two to three times a week, which was associated with a 17 to 19 percent deceased in risk for heart disease, stroke, or blood clots, compared to women who reported little or no physical activity.
- Daily strenuous exercise actually increased heart disease risk by 15 percent, stroke risk by 25 percent and blood clot risk by 29 percent, compared to women who exercised strenuously two to three times a week.
- For any activity, the optimal frequency was four to six times a week, which resulted in a 17 to 25 percent risk reduction. The most commonly reported activities in the study included walking, biking, gardening, and housework.
“Inactive middle-aged women should try to do some activity regularly,” stated Miranda Armstrong, MPhil, PhD, the study’s lead author and a physical activity epidemiologist at University of Oxford in the United Kingdom. “However, to prevent heart disease, stroke and blood clots, our results suggest that women don’t need to do very frequent activity as this seems to provide little additional benefit above that from moderately frequent activity.”
Every Minute of Moderate Exercise Helps Reduce Heart Attack Risk
Other new research confirms that even a little moderate exercise can significantly boost cardiovascular health. In a study of older adults with limited mobility, published in Journal of the American Heart Association, the researchers found that every minute of physical activity was associated with lower risk for heart attack and coronary death.
The researchers used accelerometers to track movement in 1,170 people ages 74 to 84 who had physical limitations, but were able to walk 400 meters (about 1,312 feet). Accelerometer readings of less than 100 counts per minute were classified as being sedentary, while higher numbers were deemed to be physical activity.
When the researchers calculated participants’ predicted 10-year risk for heart attack and coronary death, they found:
- For every 25-30 minutes people were sedentary per day, cardiovascular risk rose by 1 percent.
- Light physical activity (such as slow walking) was associated with higher HDL (good) cholesterol levels in people with no history of CVD.
- The amount of physical activity had a greater impact on heart risk than its intensity.
“In the past, much of the emphasis was placed on engaging in structured physical exercise,” says senior study author Thomas Buford, PhD, director of the Health Promotion Center of the University of Florida Institute on Aging in Gainesville, Florida.
“It is becoming increasingly evident, however, that encouraging individuals to just reduce the amount of time they spend being sedentary may have important cardiovascular benefits,” added Buford. “This stresses the need for regular intervals of low-level movement and to avoid sitting for excessive stretches of time.”