Endurance Training is Best
A new study shows endurance training improves heart function better than strength training. Each type of exercise has a different effect on heart muscle and heart function. Both types cause an increase in muscle mass in the left ventricle. However, endurance athletes showed better diastolic function in their left ventricle, as well as enlargement and more efficient contraction and relaxation in both of the lower chambers of the heart, or atria. The strength group actually had excessive enlargement in the left ventricle muscle and reduced diastolic function. This research shows that people aren't born with an "athletes" heart, but it is the training that creates one. Consult with a holistic health care professional to determine the correct exercise for you.
Source: Journal of Applied Physiology, April 2008