Being physically active is important to prevent heart disease and stroke, the nation’s No. 1 and No. 5 killers. To improve overall cardiovascular health, we suggest at least 150 minutes per week of moderate exercise or 75 minutes per week of vigorous exercise (or a combination of moderate and vigorous activity). Thirty minutes a day, five times a week is an easy goal to remember. You will also experience benefits even if you divide your time into two or three segments of 10 to 15 minutes per day.
For people who would benefit from lowering their blood pressure or cholesterol, we recommend 40 minutes of aerobic exercise of moderate to vigorous intensity three to four times a week to lower the risk for heart attack and stroke.
via American Heart Association Recommendations for Physical Activity in Adults.