Countless exercise programs claim to trim the thighs, abs and buttocks, but how many offer to reshape a flabby heart? According to new research, aerobic exercise does just that for patients with stable heart failure, literally turning an enlarged heart into a trimmer, more efficient organ for pumping blood throughout the body.
The research, published in the June 19, 2007, issue of the Journal of the American College of Cardiology (JACC), comes with a coda, however: It may be best to focus on aerobics and leave the weight lifting to someone else.
The study showed that when patients with heart failure did aerobic exercise several times a week, the oversized heart became significantly smaller and better able to pump blood. Researchers were surprised to find that those who added weight lifting to the exercise routine to enhance muscle strength did not enjoy a similar improvement in the heart's size or function.
"If I were to choose a type of exercise training for a patient with heart failure, I'd choose aerobic exercise," said Mark J. Haykowsky, Ph.D., an associate professor of rehabilitation medicine at the University of Alberta in Edmonton, Alberta, Canada. "It's aerobic training that provides the greatest benefit."
An estimated 5.2 million people in the United States have heart failure, a condition that accounts for more than a million hospitalizations each year. The total direct and indirect costs linked to heart failure exceed $33 billion annually.
In most cases, heart failure is the result of years of high blood pressure or damage from a heart attack. Over time, the heart becomes enlarged, misshapen, and too weak to effectively pump blood, a process known as remodeling. As a result, patients typically become short of breath even with very little activity.
For many years, doctors recommended that people with heart failure avoid exercise. In some cases, patients were even put on bed rest in an attempt to relieve the heart of any extra stress. Over the last decade, however, it has become increasingly clear that exercise is good for patients with heart failure, not only reducing symptoms and allowing patients to live more active lives, but also reversing some of the harmful hormonal changes that take place as the body attempts to compensate for a weakened heart.
Previous studies have reported conflicting results on the effect of exercise on the heart's size and function, however. "We knew that exercise could improve fitness and exercise capacity by about 15 percent, and that exercise could make muscles stronger and larger. But we didn't know the effects of exercise training on ventricular remodeling," Dr. Haykowsky said.
For the study Dr. Haykowsky and his colleagues analyzed data from 14 separate randomized trials involving a total of 812 patients with heart failure. The trials each quantified the effects of exercise by measuring changes in ejection fraction, the percent of blood pumped from the left ventricle to the blood vessels with each beat of the heart. About half of the studies also measured the heart's size, both at the end of diastole, the part of the cardiac cycle when the heart is relaxed and filling with blood, and at the end of systole, when the heart is squeezing and forcing blood out into the circulation.
In nine studies, patients did aerobic exercise walking or bicycling, for example for 20 to 60 minutes approximately 3 times a week, at an intensity equal to 60 percent to 80 percent of their peak ability. In four studies, patients supplemented aerobic exercise with strength training, and in one study, patients did only strength training. Study participants were clinically stable but had markedly abnormal heart function, with an average ejection fraction of just 23 percent. (A normal ejection fraction is 50 percent or greater.)