The Heart as a Muscle
The heart is a muscle, and as with any muscle, must be exercised to stay strong and working. After two to three months of aerobic exercise on a regular basis (three times a week for 20 or more minutes), the heart thickens, pumping more oxygenated blood with each beat. The arteries expand in diameter, allowing for greater blood flow. The working muscles of the arms and legs become efficient at using oxygen from the bloodstream. Exercise capacity improves tremendously. The major risk factors for heart disease are reduced by aerobic exercise. Higher levels of HDL (the good cholesterol) are produced, and the arteries have less plaque. The resting heart rate decreases, resulting in the same amount of blood pumped each day but with less wear and tear on the heart. Numerous studies indicate that aerobic exercise reduces depression and anxiety, and calms the mind. Sleep habits improve over a period. In addition, a Harvard University study of alumni men suggests the more active you are, the longer you will live.