Want a definition of crazy?

Try this: Three men - two North Americans and one Chinese national - decide to test their marathon running skills by traversing the Sahara Desert in 80 days. That's 4,300 miles through six countries, battling 140-degree daytime temperatures, nights in the 30s and such inconvenient truths as blinding sand storms, frayed nerves and regional politics.

Such is the gist of Running the Sahara, a documentary that will have its regional premiere Thursday at the Starz Film Center.

Even avid runners will find this film astonishing, not just for what the three ultra-marathoners accomplished but that they would even try such a feat.

Directed by Oscar-winner James Moll and narrated by Matt Damon, Sahara follows the exploits of Charlie Engle from North Carolina, Ray Zahab from Ontario and Kevin Lin from Taipei. The three men were already friends when they decided to put their bodies and common sense to the test. They wanted to be the first people to run across the Sahara.

Why? That question is never answered, except perhaps in the sense of British climber George Mallory's quip about climbing Mount Everest: "Because it's there."

The men start out in Senegal and run through Mauritania, Mali and Niger. They log up to 100 miles a day, running on roads when possible but often traversing the bleak, arid sand and towering dunes.

Their support team includes a physical therapist, a doctor and a logistics leader. The latter will prove the most valuable of all.

The character-driven film builds momentum and tension around the three runners: Gruff, uncompromising Engle; stoic, jovial Zahab; and focused, ethereal Lin. When the going gets tough and one wants to drop out, the others convince him to continue. Most problematic is Engle; as the trek takes its toll on his body, he becomes increasingly surly.

Running an average distance of three marathons a day isn't the main challenge the runners face. Nor is scarcity of water or the possibility of injury. The biggest obstacle turns out to be politics. The men start their journey without knowing if they'll be allowed to go through Libyan territory. Nine months of advance requests have yielded no approval.

If they don't get permission, they'll have to reroute their run through Sudan. A war-ravaged country is no place for a leisurely run.

The ultimate goal is to end up at the Red Sea in Egypt.

Director Moll's camera captures the intimacy, spirituality and physical toll the running takes on the men. He also captures some of the astonishing beauty of the desert, from sunsets to camels to welcoming natives. The image of the men running past the pyramids of Giza is spectacular.

Periodically the runners engage in confessionals, telling the camera their deepest hopes or fears, even if they haven't told their colleagues.

In the end the journey, budgeted at 80 days, lasts more than 100.

You needn't be a runner to appreciate Running the Sahara, which is less about sport than the human capacity for endurance. What drives us to accomplish our goals? What inspires us to make our goals so lofty? How do we measure success?

When the film is over, you feel as if you've run every step of the way with the main characters. You're exhausted, exhilarated and a little confused.

Running the Sahara

* When and where: 7:30 p.m. Thursday, Starz Film Center, 900 Auraria Parkway

* Grade: B+

* Cost: $35

* Of note: There will be a pre-screening reception at 7 p.m. and a post-film Q&A with runner Ray Zahab. Tickets can be reserved at NEHST.com