Exercising Just Three Days May Provide Heart Attack Protection

December 11, 1998

GAINESVILLE --- It's mid-morning on Cape Cod and the thermometer has barely climbed above 50 degrees, but 72-year-old Joseph Sullivan is out walking. Every day he puts his headphones on and walks two or three miles around Cape Cod's Kelley Park.

"I love to go out and get some fresh air," Sullivan said "It also helps me to stay in relatively decent shape."

But Sullivan is doing more than just staying physically fit. He is generating in his heart a protein called Heat Shock Protein 72, or HSP72, which protects against injury in the event of a heart attack.

According to a recent study by University of Florida researchers, less than a week's worth of walking, jogging or cycling can help the heart produce enough HSP72 to protect it against the damage done during a heart attack.

"We've done studies that indicate that as little as three days of exercise can provide protection," said Scott Powers, a professor in UF's department of exercise and sport sciences. In rats tested at UF, as few as five days of exercise produced almost the maximum amount of HSP72 that cells can hold.

"It raises the possibility that this could be true of humans, too, and we think that this is very exciting," Powers said.

HSP72 is in a family of proteins that form in the cells and protect organs in the body, such as the heart, against the type of extreme stress that a heart attack can cause. During stress, scientists believe, HSP72 can stabilize and refold damaged proteins, which is vital to preserving the heart if blood circulation is cut off.

"The whole problem of a heart attack is that if cells die, they're gone forever," Powers said. "What this heat shock protein does is to prevent the cell from dying from stress that would kill cells that didn't have the same level of stress protein. You're wounded, but you don't die."

Funded by the American Heart Association-Florida Affiliate, the series of studies Powers performed, some of which were published in November's American Journal of Physiology, were among the first to examine the effects of exercise on the heart "in vivo," or inside the bodies of live animals.

"A lot of studies take the heart out of the body and study it in an artificially created condition," Powers said. "Certainly, there's a lot you can learn from that, but many people argue that it doesn't mimic normal physiology well."

UF researchers induced heart attacks in two groups of rats: one that had trained on treadmills and one that had not trained at all. The untrained animals fared much worse after the induced heart attacks, a factor that Powers attributes to the approximately 500 percent increase of HSP72 in the trained rats.

"These experiments are the first to demonstrate that this actually works in the body," Powers said. "It's long been believed that exercise protects the heart, but I think these experiments actually provide good evidence that exercise is indeed cardio-protective in terms of being able to withstand a heart attack because of this stress protein."

Although regular exercise has other health benefits that can prevent heart attacks or protect the body in the event of heart attack, Powers said HSP72 plays a large role in protection, and because it can be synthesized so quickly, it is never too late to begin exercising.

Powers recommends performing endurance exercises such as walking, jogging and cycling for at least 30 minutes a day because the heat generated during endurance exercise plays an important role in the synthesis of heat shock proteins. However, he warns that keeping up with an exercise routine is essential because the proteins can be depleted as quickly as they are created.

"These proteins don't stay around very long," he said. "You have to continue with the exercise, or you lose the protection."

University of Florida

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