When you want to talk to someone about ultra-endurance events, you talk to Dean Karnazes. The best-selling author and frequent Outside magazine cover dude has literally written the book (Ultramarathon Man) on the sport of ultrarunning. He drew widespread attention in the running world with his feat of running 50 marathons in 50 states in 50 days. He's now in the middle of completing a series of five desert runs around the world, and he has plans for another "huge event" in 2009 that he's keeping secret for now.

So what's the appeal of all this running?

"I'm doing what I love," he says. "I had a corporate job where I made a lot of money and I hated it. Now I've managed to run for a living-I don't make as much money-but I love it."

Figuring out why we love it is the tricky part. Karnazes sounds like many endurance athletes when he describes the sport's appeal.

"People are looking for meaning in their life beyond their jobs," he says. "It's a way for them to challenge themselves...to aspire to greater things."

Whatever the reason, more and more athletes are discovering the joys of ultrarunning, adventure racing, 24-hour bike rides and an endless list of other endurance events that are pushing the limits of everyday age-group athletes. Sure, not everyone has the means to climb Mt. Everest, swim the English Channel or run 50 marathons in 50 days. But a steady rush of athletes continues to move up to from 5Ks and 10Ks to marathons and Ironman triathlons. A smaller but substantial number are finding the appeal of pushing those boundaries even further.

There are now more than 400 ultrarunning races across the country, generally defined as longer than a marathon. One of the best known, the Western States 100 Mile Run, received more than 1,300 applications for its 400 spots in the 35th annual running this year.

The National Ultra Endurance Race Series features eight 100-mile mountain bike races held in mostly mountainous parts of the country-with the exception of our home state, which plays host to the Lumberjack 100 each year in Udell, near the Big M Ski Area (see page 18 of the July issue for a story on this year's event).

In the running realm, Dances With Dirt is the ultra event with the most colorful past and present. The September event consists of two parts: a team relay (with themes and costumes) and and an ultra marathon event of 50 miles or 50 kilometers. The team portion sells out every year, including this one. The overwhelming success of the event in Michigan has led event organizers at Running Fit Adventures to expand into Indiana and Wisconsin over the past two years with Dances With Dirt - Indiana (Gnawbone) and Dances With Dirt - Devil's Lake (Baraboo, Wis.)

One of Michigan's most enduring endurance athletes is Bruce Purdy of Manchester. Purdy has been running since 1980 and in those twenty-eight years has completed 182 marathons and 210 ultramarathons, including the Western States 100 Mile Run and every North Country Trail Run (18 in all).

Purdy began running ultra marathons when he got bored with the marathon distance. He did 15 marathons before jumping to the 50 mile distance. Now he does both, and also competes in triathlons.

"Ultramarathons are more about adventure than time," Purdy said. "And each adventure presnts its own set of challenges. "I am always nervous the night before and I'm glad about that because it makes it more fun."

Purdy enjoys the ultra events because they are more social than a standard marathon.

"You have to keep your mind active. I talk to people a lot along the way, joke around, think about fun stuff like what I would do if I won the lottery." Purdy uses these techniques to help others get through tough spots too.

"I enjoy helping other people get through their first ultra distance event, helping them to rach a goal they scan truggle with in the midst of the race.."

Which illustrates the need for a larger level of commitment at the longer distances.

"You can fake your way through a marathon, if you're in decent shape," says Karnazes. "You can't fake your way through an ultra."

Purdy said there is a distinction between the levels of ultra running as well.

"The 100-mile distance is totally different than the 50. It is 75 percent mental," he explained. "You have to keep putting forth the effort even when your body wants to stop, challenge it to get to the next aid station," where ultra runners stop, hydrate and fuel up for the next leg of the race. "Everyone cries at the finish," he said, "the emotions of working through the pain just come right to the surface once you are done."

That emotional release is a large reason why athletes do what they do. In May, a study out of Germany once again brought the idea of a "runner's high" back into discussion. For year's runners and other endurance athletes extolled the glories of exercise, and scientists theorized that chemicals released by the brain called endorphins would make and athlete feel better, even produce a high in some cases.

You'd be hard pressed to find a serious athlete who doesn't seek out this endorphin buzz. Problem is, there's never been any scientific proof.

That is until now. In a report published in the journal Cerebral Cortex, Dr. Henning Boecker described how his study used PET scans and chemicals that measure endorphins in the brain to determine test athletes both before and after a two-hour run.

The sample was rather small (10 runners), but Boecker discovered that endorphins were indeed produced and had attached themselves to parts of the brain associated with emotion.

"Some people have these really extreme experiences with very long or intensive training," Boecker told the New York Times.

"You could really see the difference after two hours of running," he said. "You could see it in their faces."

That's an experience most endurance athletes recognize. But does the possible proof of something that most athletes intuitively know mean make much of a difference?

Perhaps. Some athletes report never feeling the "runner's high," and the lack of pleasure derived from exercise is one of the biggest reasons people stop. If researchers can better understand how endorphins work, athletes may better be able to use them to their advantage.

Until this happens, anecdotal evidence will have to suffice to convince people of the benefits of endurance sports. And if the number of athletes and events are any indications, it seems to be working.