If you're among of the millions of Americans who dutifully carve out 30 minutes a day for the moderate-intensity exercise recommended by experts based on the idea that you're doing all you can for your heart, you're in for some disappointing news.
An analysis published in the journal Circulation finds that amount of activity may not be good enough.
Researchers reviewed 12 studies involving 370,460 men and women with varying levels of physical activity. Over a mean follow-up time of 15 years, this group experienced 20,203 heart failure events. Each of the participants reported their daily activities, allowing the team to estimate the amount of exercise they were doing.
They found that those following the 30-minutes-a-day guidelines issued by the American Heart Association had "modest reductions" in heart failure risk compared to those who did not work out at all. But those who exercised twice and four times as much had "a substantial risk reduction" of 20 percent and 35 percent, respectively.
The findings challenge the notion of a 30-minutes-a-day magic number for exercise. Instead, research found that physical activity and heart failure may be what they called "dose dependent," meaning that higher levels of physical activity appeared to be linked to a lower risk of heart failure.
Jarett D. Berry, senior author of the study and an associate professor at University of Texas Southwestern Medical School, said the study shows that physicians and health policymakers should consider making stronger recommendations for greater amounts of physical activity to prevent heart failure.
Heart failure, which occurs when the heart cannot supply enough blood to the body, affects 5.1 million adults in the country. "In contrast to the dramatic reduction in coronary disease that we've seen in the population, the incidence of heart failure remains relatively unchanged," Berry said.
American Heart Association guidelines recommend that middle-aged adults engage in at least two hours and 30 minutes per week of exercise such as brisk walking. Berry said walking 30 minutes a day, for instance, may not be enough for a middle-aged person with hypertension, which increases the risk of heart failure. Those with diabetes or a history of heart failure also would benefit from talking with their doctors about increased physical activity.
If there's no way you can cram in 300 to 600 minutes of exercise a week, don't despair. Plenty of research shows that lower amounts, even microbursts of intense 10 to 15 minutes of activity, can be beneficial.
In fact, the Centers for Disease Control and Prevention notes that one minute of vigorous activity is about the same as two minutes of moderate activity, so you can do a mix of the two each week (see boxes at right).