Inactivity is one of the four major risk factors for heart disease, on par with smoking, unhealthy cholesterol, and even high blood pressure. Like all muscles, the heart becomes stronger and larger as a result of exercise so it can pump more blood through the body with every beat. Exercise does not increase the maximum heart rate, but a fit heart can pump more blood at this maximum level and can sustain it longer with less strain. The resting heart rate of those who exercise is also slower, because less effort is needed to pump blood. For preventing heart disease frequency of exercises may be more important than duration.
Exercise even helps reverse some of the effects of smoking.
Children should be especially encouraged to exercise every day to prevent heart disease later in life. Effect on Coronary Artery Disease and Cholesterol Levels . A recent study reported that moderate dietary changes improve cholesterol levels and so lower the risk for coronary artery disease only when an aerobic exercise program is also followed. It may take up to a year of sustained exercise for HDL levels to show significant improvement. Even moderate exercise, however, reduces the risk of heart attack, but in terms of raising HDL levels, more is better.