Study suggests there could be too much of good thing for hardcore runners

A study published Monday out of Copenhagen, Denmark tracked 1,000 runners and 4,000 non-runners over a 12 year period.

It found mortality rates higher for non-runners than for runners, but also relatively high for those who ran faster and further regularly.

Tonya Dowda has a mindset a lot of regular runners share.

"Just do it for stress relief," she says. "It's wonderful!"

Told about the results of the study, she says, "The Greeks had it right... everything in moderation."

Dr. Rob Schwartz does research for the Minneapolis Heart Institute Foundation. He says the study's results make sense.

"Well, I think the Danish study is interesting because it supports a number of other studies that are now coming forward, and essentially saying that there is too much of a good thing," Schwartz says.

Specifically, the Danish study found light to moderate runners -- defined as one to 2.4 hours a week, running a leisurely 12-minute mile -- had far better mortality rates than non-runners.

But for strenuous runners -- those running more than four hours a week at an 8.5-minute-mile pace or faster -- mortality rates evened back out.

"The question is, what is the risk?" Schwartz says. "The risk is not huge. It just is higher or equal to what it might be if they were sitting on the couch."

The Danish study lines up with what Dr. Schwartz himself found in a recent of marathoners. He found that those who ran at least one a year for 25 years had more plaque in their cardiac arteries.

The theory is that more strenuous running overworks and damages those arteries, suggesting there can be too much of a good thing.

But Dr. Schwartz acknowledges getting regular marathoners to change their ways is easier said than done.

"I can't tell them anything," he says. "As you know telling a marathoner not to run is like telling someone not to breathe. So they're going to run, just be aware that there may be a price to pay."

And runners like Dowda will tell you that there's so many benefits to running, maybe an equal mortality rate is fine.

"I'd keep running even with the statistics," she says.

Researchers admit there's a lot more work to do because so many variables are involved. The bottom line is that running and jogging are good things to do, but like anything else, be careful about overdoing it.