Aerobic exercise, such as brisk walking, biking, and swimming, is good for the heart. Strength training, also known as weight training or resistance training, also has cardiovascular benefits..

"Strength training maintains and may even increase muscle mass, which people tend to lose as they age," says Dr. Rania Mekary, a visiting assistant professor of surgery at Harvard-affiliated Brigham and Women's Hospital and assistant professor at MCPHS University. Increased muscle mass has a trickle-down effect that benefits blood vessels and the heart.

Boosting muscle mass speeds up metabolism, which helps people burn more calories, even at rest. A faster metabolism also helps prevent weight gain, which puts extra strain on the heart. Strength training seems to be especially important for keeping off belly fat. This so-called visceral fat, which surrounds the internal organs, is particularly dangerous.

Mekary and colleagues at the Harvard T.H. Chan School of Public Health found that healthy men who did weight training for 20 minutes a day had less of an age-related increase in abdominal fat compared with men who spent the same amount of time doing aerobic exercise.

Strength training can help control blood sugar levels by drawing glucose from the bloodstream to power muscles. High blood sugar, the hallmark of type 2 diabetes, is also a leading risk factor for heart disease. Building more muscle mass also makes the body more sensitive to the effects of insulin, the hormone that regulates blood sugar levels.