The event known as the U.S. Challenge involves pitting small teams from some of the largest companies in the nation against each other in tests of physical endurance and mental agility.

So, when Greg Martin notes that he and his fellow members of the Roanoke County government team entered in this month's event are "fairly competitive," he may have pronounced the understatement of the event before it even begins today.

Roanoke County joined with other governments, the Roanoke Valley Economic Development Partnership and the Roanoke Valley Convention & Visitors Bureau to lure the second annual U.S. Challenge to the Roanoke Valley. It will be held through Saturday.

Although details of the 72-hour competition are secret until it begins, last year's event -- and similar ones that have been held in Europe for several years -- involved physical contests such as running, kayaking and bicycling combined with a variety of intellectual tests and puzzles. They are designed to build team spirit and cooperation among employees of the participating companies.

For the Roanoke Valley sponsors, drawing the 50 or so companies that have sent five-person contingents to the event is a giant public-relations coup. It will bring national media attention, but perhaps more importantly give up-and-coming employees of some of the country's largest firms a chance to become familiar with the region's amenities.

Someday, the sponsors hope, that will translate into a favorable decision about locating a business here.

Martin's teammates understand the big picture, but, deep down, they applied for the county's team because they like to compete and win.

"It's a once-in-a-lifetime opportunity," said Natalie Dibling, a 26-year-old Roanoke County firefighter and emergency medical technician. "How many times will you get to compete in a race with people from Fortune 500 companies?"

Jimmy Chapman, the team captain and a Roanoke County police lieutenant, agreed that the competitive challenge is a strong draw but noted there are a variety of attractions to such an event.

"You meet people from different areas," gaining an understanding of co-workers' jobs, said Chapman, 37. Teams also raise money for St. Jude Children's Research Hospital. The Roanoke County group received more than $3,000 in pledges.

But, he noted, "I'd have to piggyback what Natalie said. This is a once-in-a-lifetime opportunity to compete at this level, this size."

Martin, whose day job is manager of Camp Roanoke, operated by the department of parks, recreation and tourism in the Dixie Caverns area, said "nobody wants to be passed on the trail."

The idea of contending against teams including Navy SEALS and NASA employees whets contenders' competitive appetite, he said. Not to mention that his co-workers have teasingly told the 34-year-old that "if I don't finish, that's it, I can't come back to work."

Several other Roanoke Valley companies and governments are fielding teams as well, including the city of Roanoke, National College of Business and Technology, Delta Dental of Virginia and Roanoke College. There's also a team made up of members of Roanoke County firefighters who weren't chosen for the county team but were determined to participate, Dibling said.

Marcus Ordonez, the relatively new assistant director of recreation for the county, conceded that, like the other members of the team, he had never heard of the Challenge until the county became involved in its sponsorship.

"The county worked to get this to showcase the Roanoke Valley as a great place to live and raise a family," said the 31-year-old former James Madison University football player.

"We represent the county as part of our job every time we put on the uniform" or go to work, Chapman said, but the Challenge offered an additional way to "represent ourselves and the larger picture."

The fifth team member is 29-year-old Michael Roth, a county firefighter and medic.

"Everybody brings different attributes to the team," Martin said, and the weeks of interaction have helped them come to depend on and trust each other.

"It's really been a good way to know each other," Ordonez said. "We know our strengths and weaknesses," and are ready for the Challenge to begin.

And they've come to appreciate one of its core values: "You never cross the finish line by yourself," Martin said, "you're always with a teammate at the finish."