Endurance Exercise May Protect Against Injury In Heart Attacks
GAINESVILLE, Fla. — Endurance exercises such as running and cycling may protect older people from cardiac injury during a heart attack, according to a new University of Florida study.
Through experiments with rats, the researchers discovered that exercising one hour a day for three consecutive days offers the heart just as much protection in the animal as if it ran five days a week for 10 weeks, said professor Scott Powers, director of the Center for Exercise Science and a contributing author to the study.
The finding contradicts the conventional belief that it takes weeks or even months of exercise training to reap the benefits of exercise; it turns out protection against a heart attack can be obtained in just three days and lasts more than a week.
“You stay protected up to about nine days,” said Powers. “By day 18, you’re completely back to where you started. So the only way to maintain it is to be active.”
In the study, which appears in this month’s issue of the journal Experimental Gerontology, young and old rats ran on a treadmill at approximately 60 to 70 percent of their exercise capacity. Exercise increased their levels of the antioxidant superoxide dismutase, which provides cardiovascular protection. Additional experiments have shown that exercise-induced increases in this antioxidant are critical for the heart to develop the full protective benefits of exercise.
Powers said that in approximately 90 percent of heart attacks, blockage created in the vessels triggers a clot that can damage the heart. “If you don’t break down the clot, the heart
cells are going to die,” he said.
Powers added that even if the clot dissolves naturally, damage still occurs when blood flow is restored to the heart because the oxygen level is increased and forms an unhealthy abundance of free radicals that damage the heart muscle. This process, called ischemia reperfusion injury, makes the heart weaker and decreases its working capacity, according to the study.
Powers said that’s “because you can think of the heart as the engine that runs the car. So if you chop off cylinder after cylinder from the engine, eventually it’s going to be underpowered.”
In humans, exercises such as cycling, swimming, running and walking may cause heart muscle cells to produce more antioxidants that protect the heart during the insult of a heart attack.
Powers and John Quindry, postdoctoral fellow and a contributing author to the study, also concluded that exercise protects against cell death caused by apoptosis, or programmed cell death, which had been previously unknown.
Powers said the study may help to determine why endurance exercises provide the heart protection. Once that is known, researchers could design better exercise strategies, or develop a drug approach to turn on the genes that are activated during exercise.
“That would be extremely useful for people who are wheelchair-bound, aren’t ambulatory, or just people who have orthopedic problems or won’t exercise,” said Powers.
Li Li Ji, a professor of kinesiology at the University of Wisconsin-Madison, said the UF research is important because it shows that independent of age, endurance exercise can reduce injury sustained during a heart attack.
“These experiments for the first time demonstrate that exercise can protect the heart against ischemic insult in both young and old animals,” he said.
The study was also conducted by doctoral candidates Joel French and Youngil Lee and former UF assistant scientist Karyn Hamilton.