MASON COUNTY, Texas - Extreme off-road endurance racing is an adrenaline rush that puts man and machine to the test.

"Punishing, exhilarating, satisfying when you do finally hit the checkered flag," driver Jay Eakin said.

Not only are drivers trying to hit the checkered flag, sometimes they're just trying to finish the race.

"Every racer helps every racer, until you're out on the race course," Eakin said.

The Bixby resident is just one of the Oklahomans competing in the Dirt Riot Endurance Racing circuit. The circuit is broken into five regions across the country. These drivers are facing off in the central United States region in the Texas Hill Country.

"It's a mix of desert racing and a rock crawl. In Oklahoma rock crawling and off roading and jeeps and things are very popular," Eakin said.

Named for its giant granite rock formations, Wolf Caves is a 400-acre, boulder-strewn course, and it is brutal.

"This is the toughest course in the series," Johnson said                                                                                       .

Drivers speed through mud and dust past the mesquite trees but suddenly the stretches of speed are followed by the much slower strategy of rock climbing. Drivers have to maneuver around, or over formations with unique names like Goat Head, T-Rex, and Monument Rock.

"It's six inches one way or the other, and you're stuck," said driver Marc Davis.

"Rock crawling, I absolutely love rock crawling, it's slow," said driver Jessy Greenland. "It makes your mind work. You have to focus a lot."

Greenland is the only woman from Oklahoma racing on the circuit. Kent Johnson is her mechanic and co-pilot.

"It's just the challenge of keeping it running and making it go and being the guy that has to be depended on to fix it," Johnson said.

During a race, competitors get in as many laps on the course as they can, during a set amount of time. They place based on their best lap time. But the rough terrain is not only hard on the vehicles, it also tests the stamina and endurance of the drivers.

"I'll be Ibuprofen King tonight and tomorrow," jokes driver Marc Davis. "It's just, by Monday at work, I look like I'm 90. It beats you to death."

"You're beat up. You feel like you just got out of the ring of a heavyweight boxing match when you're done racing," Eakin said.

Despite the beatdown and the heat, they love the camaraderie as well as all the challenge.