Desert High

His pack weighs in later at 22 pounds, just above the 20-pound average for a 4 Deserts race. Pete's is 19, and Mike's is just under 16, a fact that results in a lot of chest-puffing until it's announced that the lightest pack in the competitor field belongs to Juan Encina, a member of Trifecta's rival team. The Chilean runner's 11-pound pack hugs tight against his small, muscled frame.

Frank has real reason to be anxious about his pack weight: He has a stress fracture in his right shin. He doesn't mention the injury at his pre-race medical review, but he doesn't want to hold anyone back. Still, he's hesitant to bring it up again with his teammates. When Frank finally finds the right moment to mention it to Mike, however, their exchange is the equivalent of two soldiers swearing to drag each other back from the battlefield.

"Look, Frank, worst-case scenario," Mike says, "at a checkpoint, you couldn't go on and finish the stage for whatever reason, and Pete and I went on, it would just mean as a team we're not eligible to place in the overall teams thing. ... And if your leg feels better, you can start with us the next day; you just don't get a medal at the end."

Frank replies: "Right, and I wouldn't qualify for Antarctica. I'm convinced that whatever happens, I'll finish. ... Either I'll walk or I'll hobble, but I'll finish."

"Look, the only way we would go on without you is if you weren't gonna finish the race."

A long pause. Frank seems out of words. "Well ..."

"-- 'Cause we'd just wait."

Another pause. "Well, that's, that's really cool of you." Frank adjusts his shoelace.

"What're you gonna do, mate? We're a team."

RACE DAY DAWNS WITH THE CONTESTANTS GATHERED UNDER A GIANT YELLOW BANNER beneath a deep blue sky. A five-member Chilean band serenades the crowd with tunes from the indigenous Mapuche. The musicians play reed flutes and tiny guitars, and look out with mild amusement at the spectacle before them: runners decked out in neon spandex sprouting tentacles of "hydration systems" and waving spindly trekking poles.

The 60 men and 11 women, 20-somethings to 60-somethings from 18 countries, are racing for at least as many reasons. For Dean Karnazes, 45, a professional endurance runner whose athletic résumé includes running 50 marathons in 50 days, it's about his reputation. He and six to 10 other front-runners will jockey for position at each stage. Karnazes will trade the lead five times before edging out his main challenger, Rob James, an amateur British runner known for his bright green shoe covers. Adil Chaudhry, 50, an American living in Singapore, wants to take a long desert stroll with his iPod, listening to travelogues and pondering the scenery. Singaporean P.J. Toh, 32, wants to collect visuals, so he hauls along a four-pound Canon digital single-lens reflex camera. And Briton Mimi Anderson, 45, writes her last pre-race blog entry about the importance of a good waxing and manicure before a run. For Trifecta, however, there's only one reason to run hard in the stunning Chilean desertscape: to win a ticket to the next race.

The starting gun fires, and some runners tear toward the horizon, but Frank, Mike and Pete put their heads down. Day One starts at 11,000 feet, a real home-court advantage for the altitude-acclimatized Chilean team. The course drops down, following the ruins of an ancient highway that once stretched from Argentina to the Pacific Ocean via Chile; it leads through deep-cut canyons and finishes on a blistering hot plateau.