On the next couple of laps Frahm tried to think more about the run itself -- until she found herself singing children's songs. "'The Wheels on the Bus,' 'Bingo' -- to take my mind off things."

Mile 68 or so, midway into her fifth lap, after she'd been running 14 hours and it was starting to get dark was when the pain started kicking in ("My feet were burning"). On the seventh lap, phantom trails tried to lure her into the forest. By the eighth and final lap?

"I swore up and down all during the eighth lap that this was the craziest thing I'd ever done," said Frahm, who holds a doctorate in chemistry. "Why would anyone ever want to do this again?"

"This" being to run 100 miles. At one time. Without stopping.

The question seems a logical one, yet on April 5, at 5:59 a.m., 234 runners stood in the dark under threatening skies at Umstead State Park eager to run 100 miles. To head out in the dark, run till sunrise, run throughout the day, run into the evening, run into the night. The fastest ones would be able to finish in time for the evening news. Most, though, would plod on throughout the night and into the morning, wrapping up about the time many folks were getting out of church.

Running continuously, from Saturday morning cartoons to Sunday dinner.

In a world of crazy endurance events -- from Ironman triathlons (swim 2.4 miles, bike 112 miles, then run 26.2 miles), bike races across the U.S. (3,000 miles in eight days) and adventure races that include every event under the sun over the course of a week or so -- ultramarathons are among the craziest. Crazy, but catching on fast. The esoteric event has gone from being the pastime of a fringe few to the next logical step for runners seeking a new challenge. According to UltraRunning magazine, last year saw 354 ultras (defined as races of 31 miles or longer) in North America. The magazine didn't report the total number of people who entered the races, just the number who finished: 25,816.

The Umstead 100 Endurance Run epitomizes the popularity of the ultra.

"We could easily get 500 or 600 runners if we didn't have a registration cap," says assistant race director Joe Lugiano.

As it is, the ceiling of 250 runners -- to keep the race manageable within the confines of 5,500-acre Umstead -- was reached three days after registration opened in September.

Until 2003, Jennifer Frahm was pretty much a gym rat. One day, leaving the gym in Rochester, Minn., where she worked at the Mayo Clinic, she picked up a flier for a half-marathon. Some friends ran and it looked like fun, so she signed up. Then she thought, oh, what the heck.

"I'm going to be running all these miles anyway," she reasoned, "why not get my one marathon out of the way?"

She had such a good time in the 5 hours and 2 minutes it took her to run the Chicago Marathon that she signed up for another, then another. After 20 or so, and after getting her time down to 4 hours, she decided she needed another goal. So last year, she did the Umstead 100's 50-mile option, which only made her want to do the full 100.

A common thought process, says Richard Keefe, a sports psychologist at Duke who counsels Blue Devil athletes.

"Some people just love to set a goal, then work hard to reach it," Keefe says. When they achieve one goal, they need to move on to the next, which is common in any number of areas, says Keefe, be it work, your kids, video games. What's slightly different for athletes is the accompanying buzz they get, the oft-touted endorphin high.

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