ST. LOUIS -- Everyone knows that exercise is good for you. But is it possible to exercise too much?
The St. Louis Post-Dispatch reported that a growing body of evidence suggests that it might be.
At least two studies in recent years have found permanent scar tissue and structural changes in the hearts of otherwise healthy men who are avid marathoners. Another study showed that running up to 20 miles a week at an easy pace prolonged life but that running more and at higher intensity produced diminishing results.
Some hard-core endurance athletes aren't buying it, including Beverly Ofsthun, 49, of O'Fallon, Mo., who has done 20 Ironman triathlons -- a 2.4-mile swim, 112-mile bike ride and 26.2-mile run.
"I know a sports-med physician, and until he says, ‘No, you shouldn't do that,' I'm going to continue doing that," Ofsthun said.
Tom Reich, 71, of Manchester, Mo., has run close to 100 ultra-marathons that typically range from 50 to 100 miles.
"I guess I'll keep doing it until they find me on the side of the trail rolled up in a little ball and mummified," he said.
Cardiothoracic surgeon Seiichi Noda has done four Ironman races and is training for the Hawaii Ironman in October. He appears ready to scale back.
"Once I do this race, I'll probably put myself in the moderation category," he said.
The number of endurance athletes has risen sharply in recent years. Thirty-five years ago, fewer than 50,000 people participated. Now, the number is well over half a million.
The growth of endurance sports is so new that there isn't a lot of research on what it does to the heart.
Years ago, scientists began studying runners' hearts immediately after they finished marathons. They found that many of the runners had structural changes in their hearts that went away in the weeks following the race.
Later studies have indicated that chronic endurance training and competition causes repeated structural changes to the heart. Scientists say those changes can weaken the heart muscle and cause it to become permanently scarred and arrhythmic.
One study compared 102 men who did not run to 102 healthy male runners who ran at least three marathons during the previous three years. It found that about 12 percent of the runners had scarring on their heart, three times more than the non-runners. The marathoners also had more heart attacks and heart- or stroke-related problems than the non-runners during the following two years.
Reich maintains that he has not heard of any ultra-runners with heart problems.
"And I've been around a lot of ultra-runners," he said. "I haven't seen any conclusive evidence yet. It seems nebulous, what they're pointing fingers at."
St. Louis psychiatrist Ed Wolfgram, 79, has done more than 60 marathons and 17 Ironman races in the past 30 years. In January 2008, he had open-heart surgery to replace his aortic valve. He returned to racing, finishing three Ironman races later in 2008.
Three months after that, he began experiencing arrhythmia. He has had two ablations and three cardioversions to try to correct it. None has worked.
"I'm not so sure that the research thus far means it compromises one's longevity, that [excessive exercisers] don't continue to live long and healthfully," he said. "They most likely don't have any obesity or diabetes or hypertension. So it would be helpful if you get benefits without any of the penalty."
Experts say that overall, endurance athletes have better health, quality of life and longevity than people who are sedentary.
"The take-home message here is that exercise is great for you," Noda said. "Even people who exercise to the extreme are still better than those who didn't.
"My goal is to be 80 and still exercising," Noda added.