Our heart is a muscle and exercise is one of the things you can do in order to strengthen that muscle. When you exercise is makes the heart pump more efficiently. It doesn't have to be a all-out, high-energy exericse class in order to help heart health. Just a brisk walk increases your heart rate and improves circulation. If you walk 3 or more hours a week you can decrease your risk of a heart attack by 35 percent.
References:Voltolina, Vanessa,p. 123, WeightWatchers, Sept./Oct. 2011