IF YOU HAD WON ONE OF endurance sports' most grueling contests, twice, and your chief rival had won it once, and if his tanned mug and chiseled pecs had appeared on the covers of Runner's World, Trail Runner, Marathon & Beyond, SF Weekly, and this very publication, and he had bantered with not one but two late-night talk-show hosts and had been granted a 44-city book tour and a product-endorsement deal from a national cosmetics company and a major sponsorship from The North Face, and you had not—if, in fact, you'd gotten only one late-night TV appearance, along with The Tony Danza Show, as well as some free sneakers and sports drinks, and you'd had to share your big 60 Minutes segment with your rival—you could go about things one of two ways. You could shrug and chalk it up to "that's how the shallow world works; he's a sex symbol and I'm not," or you could set out to prove that you deserve some attention around here.

If you were Pam Reed, you'd choose the second option. Which is why, just north of Tucson, Arizona, on a Sunday morning in late March, the 44-year-old couldn't remember if she was running north or south, or what she was supposed to do when she got there. By that night, she was still running. She'd been running since Friday morning without stopping—except to pee, standing up, among the roadside brittlebush—for a total of 238 miles so far, and her goal of 300 miles dangled at least another night away. The pee thing was an art she'd perfected during 15 years of ultramarathons, and she's scarily good at it, to the point that it involves no undressing and no sticky legs. She hasn't yet worked out how to pee while running, as many men do, but don't put it past her.

Reed's course was a 12.5-mile-long stretch of I-10 frontage road. The plan was to run back and forth on it for 24 circuits without sleep breaks—past the casino billboards, the derelict black Dodge van, and the sign that read truck hauling. The terrain was flat and unspectacular, humming with semis from the interstate.

"God, I can't believe how long this is taking," she said, but casually, as if she were standing in line for postage stamps. Her bent arms swung mechanically. Her feet glided low over the asphalt, planting without a sound. Thin and spindly, she appeared smaller than five foot three; her face looked vacuum-wrapped, like skydivers' faces look when they're free-falling, an image aided by the upward spikes of her short blond hair. Reed's pretty blue eyes shone with determination. Although there were no competitors around to spur her on, she did have one specter in mind: Dean Karnazes, a fellow ultrarunner who'd appeared glowing and nearly naked on the cover of the February 2005 Runner's World. That image was enough to propel her through three sleepless nights and 45 bottles of vanilla Ensure.

Karnazes, the 42-year-old San Francisco–based president of Good Health Natural Foods, had broken Reed's two-year winning streak the summer before at the Kiehl's Badwater Ultramarathon, a grueling 135-mile race from the bottom of Death Valley to a finish line halfway up Mount Whitney. The year before that, Reed had beaten him there by 25 minutes, in a race that lasted more than 28 hours, in up to 127-degree heat. And the year before that, in her very first Badwater, Reed beat her nearest competitor by more than five hours, and the nearest woman by ten.

None of that helped ease the sting of the Runner's World cover, the latest in a mounting stack of glossies and television appearances by Karnazes. And this was all before his memoir, Ultramarathon Man: Confessions of an All-Night Runner, published in March by Tarcher/Penguin, sold 50,000 copies and climbed to number 18 on the New York Times bestseller list.

"When I won Badwater, I didn't think that much of it," Reed said the night before starting her 300-mile run. "But what bothers me is he gets a cover of Runner's World. They only did a little blurb on me."

Her feelings, she said, were not personal. "It's not him; it's our society. Dean is a really nice guy. I'm not jealous of him, but women need to get some recognition at some point. Running has politicized me."

On the cover, alongside Karnazes's heaving quads, ran the text DEAN KARNAZES WANTS TO RUN 300 MILES (WITHOUT STOPPING).

So Reed had an idea. She'd scoop Poster Boy. As a goal, it was arbitrary. Only a handful of ultrarunners had run so far in one outing, and going 300 miles without resting at all, Karnazes and Reed each hoped, could be a first.

Reed is as tough as a desert tortoise. She runs 110-plus miles a week in the Arizona sun, and she doesn't use sunscreen, her theory being that it blocks the body's evaporative cooling. Her skin is more like a hide, and it has served her well. She's given birth to three children, Timothy, 20, Andrew, 16, and Jackson, 10; stepmothered two others, 16-year-old Jonathan and 19-year-old Greg; been a high school cheerleader and run track in Negaunee, Michigan; played tennis at Michigan Tech; suffered 15 years of anorexia, including two hospitalizations; lost most of her teeth (thanks to a genetic predisposition); and become an ultrarunning phenom. Since she started competing in Ironman Triathlons in her late twenties, she's run more than 40 races longer than 100 miles, and 100-plus marathons, including two "double Bostons"—back-to-back laps of the Boston Marathon. In 2003 she broke the U.S. women's 24-hour track record and, last year, the 48-hour women's record for her age group.

All this, and in dentures.