How Safe, Moderate Exercise Can Keep Your Heart Healthy

In study after study, exercise has been shown to slash the risk of heart disease and add years to one's life, even among obese people and other high-risk populations.

While the benefits of exercise are well documented, the amount of exercise needed for those benefits to kick in is still disputed. The American Heart Association recommends at least 30 minutes of moderate-to-vigorous exercise (defined as reaching and maintaining 50% to 85% of your maximum heart rate) on most days of the week. A brisk walk, a bike ride, and light weight training all count.

But some studies have shown that even less exertion can be beneficial. A 2001 Harvard study of nearly 40,000 women over the age of 45 found that walking just 60 to 90 minutes a week cuts the risk of coronary artery disease in half.

Another Harvard study suggests that several short exercise sessions may be as beneficial as one extended session, as long as the total amount of energy expended is equal. Yet those researchers also determined that only sports and other vigorous activity—and not light exercise like walking—significantly lower the risk of coronary artery disease.

Then there's the case of the 51-year-old marathon runner with no symptoms of heart disease who had a routine heart scan and discovered that he had atherosclerosis (hardening of the arteries), which can lead to a heart attack.

A team of researchers from the University of Maryland Medical Center who studied his condition concluded that the main culprit was exercise-induced hypertension, which the study's lead author suggested is "vastly underdiagnosed."

Pulling weeds in the garden, sweeping the living room, walking through the grocery store—any form of exercise can help you gain strength and confidence. But if you want to protect your heart, you'll have to push yourself a bit harder, says Thomas Allison, PhD, an exercise physiologist and the education director of the Mayo Clinic's cardiac rehabilitation program. For maximum heart protection, shoot for 30 minutes of moderately vigorous activity every day.