April 23, 2008 -- Could a specific workout routine help tame particular forms of heart disease? A first-of-a-kind study documenting how various forms of exercise affect the heart suggests that in the future doctors may be able to tailor a patient's exercise regimen to his or her specific heart condition.
Researchers with Massachusetts General Hospital and Harvard University Health Services followed 75 student athletes for 90 days during normal team training to see how vigorous athletics affected their heart structure and function.
"Most of what we know about cardiac changes in athletes and other physically active people comes from 'snapshots' taken at one specific point in time," researcher Aaron Baggish, MD, a fellow in the Massachusetts General Hospital cardiology division, says in a news release. "What we did in this ... study was to follow athletes over several months to determine how the training process actually causes change to occur."
Baggish and colleagues divided the students into two groups: Endurance athletes consisting of male and female rowers and strength athletes made up of male football players. Researchers excluded from the study anyone who reported using steroids.
The students followed the normal training plans established by their coaches and trainers. Endurance training involved one- to three-hour sessions of rowing on the water or on gym equipment. Strength training involved weight training and drills designed to improve muscle strength and reaction time. On average, the students trained for 12 hours per week.
The researchers performed echocardiograms on the students at the beginning and end of the study to assess how their hearts adapted to a typical season of competitive athletics. Echocardiograms provide information about how blood flows through the heart, revealing important details about the organ's structure and function.
Exercise and Heart Changes
After the 90-day follow-up period, the researchers noted profound changes in the students' heart structure and function. But the changes varied depending on the type of exercises performed.
Both the right and left ventricles of the endurance athletes expanded, while the heart muscle in the left ventricle tended to thicken (but did not expand) among the strength athletes. The ventricles are the principal pumping chambers of the heart and are responsible for sending blood to the body and to the lungs.
Another significant difference involved the ability of the heart muscle to relax between beats. The heart relaxed more in the endurance athletes, but less well in the strength athletes, though still remaining within normal ranges. In general, better heart muscle relaxation is considered advantageous.
"We were quite surprised by both the magnitude of changes over a relatively short period and by how great the differences were between the two groups of athletes," Baggish says. "The functional differences raise questions about the potential impact of long-term training, which should be followed up in future studies."
Though the experiment involved healthy, young students, the researchers believe their findings could one day benefit heart disease patients who engage in exercise for recreation or rehabilitation purposes.
"The take-home message is that, just as not all heart disease is equal, not all exercise prescriptions are equal," Baggish says. "This should start us thinking about whether we should tailor the type of exercise patients should do to their specific type of heart disease. The concept will need to be studied in heart disease patients before we can make any definitive recommendations."
Researchers published their findings in the Journal of Applied Physiology.