ST. LOUIS -- Absence may make the heart grow fonder, but exercise may do something even better: It seems to make the heart younger.
At least, that's what Washington University researchers here found when they asked a dozen older folks to participate in endurance exercise training. After a year, those senior athletes wound up with a much younger heart, metabolically speaking. And, women seemed to do even better than men.
"We know that the heart deteriorates as people get older, and that's largely because they don't stay as active as they used to," said Dr. Pablo F. Soto, an instructor in medicine and the study's first author. "Past research has suggested that exercise can reverse some effects of aging, and we wanted to see what effect it would have specifically on the heart."
The researchers measured heart metabolism in sedentary older people both at rest and after giving them dobutamine, a drug that makes the heart race as if a person were exercising vigorously.
At the start of the study, the researchers found that hearts did not increase their intake of blood sugar (glucose) even in response to the increased energy demands caused by the dobutamine.
But after being subjected to endurance training for a year, those same hearts doubled their glucose intake during high-energy demand -- just as younger hearts do. The training involved walking, running or cycling for about an hour three to five times a week.
Soto said that if the heart muscle doesn't take in more glucose in response to increased energy needs, it goes into an energy-deprived state that may raise the risk of heart attack. Conversely, if it can increase glucose intake, the heart is better protected against ischemia (low oxygen) and heart attack. In another revealing finding, researchers found women may have benefited more from the training. The heart uses both glucose and fatty acids for energy. After the training, men's fatty acid metabolism dropped in response to energy demand, but the women's increased. "By that gauge, the women had a better response to exercise training than the men," Soto said. "At this point, the significance of that isn't clear. We know that in animal studies low fatty acid oxidation leads to heart muscle thickening, and that when men train, their heart muscle often gets thicker than women's. It could be that the increase in fatty acid oxidation in women's hearts with training is a reason why their hearts don't thicken as much." Participants in the study were six men and six women ages 60 to 75 who were not obese but who had been living an inactive lifestyle. They were put on an 11-month program of endurance exercise by a skilled trainer.
For the first three months, they were required to exercise to about 65 percent of their maximum capacity. After that, the program was stepped up so participants reached about 75 percent of maximum. Afterward, volunteers said they felt in the best shape they had been in years, Soto said. Next, Soto and his colleagues will investigate exercise training in individuals with heart failure. "In the past heart failure patients were told to limit their activity," Soto said. "Now more and more we're seeing there is potentially a benefit to getting them as active as possible. We want to know if heart failure patients will experience the same benefit in heart metabolism with exercise that we saw for older people." The current study appeared last month in the online version of the American Journal of Physiology. Contact reporter Roger Schlueter at 239-2465 or rschlueter@bnd.com.
