Sunday's race in Keene, N.H., is named after a New England resident who was one of the best distance runners of the early 20th century. He played a role in redefining our relationship to exercise.

Transcript

LEILA FADEL, HOST:

Hundreds of people will line up Sunday morning to run the 45th annual Clarence DeMar Marathon in Keene, N.H. The race is named after one of the best distance runners of the early 20th century, who made a surprising contribution to sports science after his death. New Hampshire Public Radio's Paul Cuno-Booth has the story.

PAUL CUNO-BOOTH, BYLINE: Clarence DeMar would train by running to and from his job at a print shop in Boston, up to 14 miles a day, often carrying a clean shirt. It paid off. He won the 1911 Boston Marathon and competed in the next year's Olympics. But all that running raised eyebrows. A doctor warned him to quit the sport. Even his fellow runners told him not to try more than one or two marathons in his lifetime.

TOM DERDERIAN: He trained more than was commonly believed humanly possible at the time.

CUNO-BOOTH: Tom Derderian is a historian of the Boston Marathon.

DERDERIAN: He ran lots of mileage, and the idea in the past was that lots of mileage would wear you out, that you would die early.

CUNO-BOOTH: It may sound strange today, but back then people thought marathons were kind of dangerous.

DERDERIAN: People came out to watch the marathon because they thought that somebody might drop dead during it.

CUNO-BOOTH: DeMar proved them all wrong.

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UNIDENTIFIED PERSON: Here they come - 184 of them. It's the start of the Boston Marathon.

CUNO-BOOTH: He competed in two more Olympics and won the Boston Marathon a record seven times between 1911 and 1930. The press called him Mr. DeMarathon.

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UNIDENTIFIED PERSON: Here he is - doesn't even look as if he's warmed up yet.

CUNO-BOOTH: After DeMar died from cancer at age 70, a couple cardiologists took a look at his heart. What they found contradicted all those dire warnings. Not only was his heart perfectly healthy, his arteries were two to three times the size of a typical person's. Dr. Paul D. Thompson is the former chief of cardiology at Hartford Hospital in Connecticut.

PAUL D THOMPSON: So that even though they had all this cholesterol, they were not narrowing. They were not obstructing. They did not block flow.

CUNO-BOOTH: The study was published in the prestigious New England Journal of Medicine. It made the front page of The Boston Globe. Dr. Aaron Baggish is a professor at the University of Lausanne in Switzerland and the former medical director of the Boston Marathon.

AARON BAGGISH: It was one of those first studies that taught us that the human body can really handle very healthfully lots and lots of exercise.

CUNO-BOOTH: Running's popularity exploded in the decades after DeMar's death. Meanwhile, a growing body of research showed that exercise actually makes us healthier and helps us live longer. Or as Dr. Jonathan Kim, a sports cardiologist at Emory University, likes to put it...

JONATHAN KIM: Exercise is truly medicine.

CUNO-BOOTH: But in recent decades, researchers have also learned more about a question that faced DeMar a century ago - whether running as much as he did might have side effects. For example, atrial fibrillation, a type of irregular heartbeat, affects some middle-aged athletes, particularly men.

THOMPSON: I've had atrial fibrillation, one of the reasons I got interested in the whole topic.

CUNO-BOOTH: This is Thompson, the Hartford cardiologist. He's also an accomplished marathoner who ran in the 1972 Olympic trials.

THOMPSON: I don't want to discourage anyone from doing a fair amount of exercise. It's just that the extreme amounts of exercise done by, you know, people like myself who've tried to be a competitive athlete all their lives has potential side effects.

CUNO-BOOTH: Studies have also found evidence of plaque buildup in the arteries of some lifelong endurance athletes. But Kim says it's not yet clear if that means anything for their long-term health. And in general, people with a high degree of cardiorespiratory fitness from years and years of intense exercise still typically live longer than everybody else.

KIM: Overall, when you look at elite-level athletes, they still tend to do better than individuals who are not as active or fit.

CUNO-BOOTH: For most of us, of course, the concern isn't getting too much exercise. It's getting too little. Research suggests even moving around a bit can make a difference, and more is generally better. In any case, many runners say they're not just doing it to stay healthy.

THOMAS PAQUETTE: It makes me feel alive.

CUNO-BOOTH: Thomas Paquette is the manager at Ted's Shoe & Sport. It's a running store in Keene, N.H.

PAQUETTE: If I don't run, I'm not the same person.

CUNO-BOOTH: Clarence DeMar lived here in Keene for part of his racing career, and he's still a local legend. The running store's animatronic mannequin is even nicknamed Clarence. Paquette says it's not just DeMar's competitive achievements that inspire him. It's also that the man simply loved running.

PAQUETTE: I see my parents. My dad just turned 80 yesterday, and my mom is 70, and they still are running too.

CUNO-BOOTH: He hopes to follow in their footsteps and in Clarence DeMar's.

For NPR News, I'm Paul Cuno-Booth.

(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.