Among the accomplishments one might hope to amass over a lifetime, running the entire length of the Sahara may not come up on many personal to-do lists.
Yet that was the grueling goal for ultra-distance runners Charlie Engle, Ray Zahab and Kevin Lin. Their exhaustive exploits are explored in the documentary "Running the Sahara," airing on Showtime (premiering Sunday, 9 ET/PT).
The three completed what's believed to be the first run across the world's largest desert.
The documentary, produced and narrated by actor Matt Damon, aims for emotional punch and visual scope. The Sahara's stark beauty, the often-terse interplay between the runners, their loved ones and support crew, and the personal toll the journey takes on everyone is captured by director James Moll, an Oscar winner for 1998 Holocaust documentary "The Last Days."
Engle, Zahab and Lin aimed at completing the equivalent of two marathons a day. By the time their six-country jaunt was through in November 2006, they had covered more than 4,300 miles in 111 days.
The idea was born, almost on a lark, after Engle and Zahab had competed in a long-distance race in the Amazon jungle. But without the intense, hard-charging Engle, 46, the motivational speaker and entrepreneur on whom Sahara primarily focuses, the run probably would never have been launched, let alone completed.
"Frankly, this thing died five times over 18 months before we got there," Engle says in an interview.
Within a week after beginning the trek in Senegal, Engle had concerns: "By Day 5, we were two days behind schedule and really struggling," he says.
"It was 130 degrees during the day. Kevin was really sick. I could see that look on everyone's face — we weren't going to make it," he says. "We stopped thinking about the future and took it one day at a time. Slowly but surely, our bodies adjusted to the stress."
Lin, 32, later wanted to drop out but was coaxed by Engle and Zahab to continue. Engle, healthy for all but two days of the race, developed a staph infection and a baseball-sized foot blister that left him hobbling toward the finish.
Moll was skeptical about the run from the start. "Frankly, I didn't believe it was possible. I wasn't convinced they would make it, but if they were going to do this, I was going to be there," says Moll, whose latest documentary, Inheritance, aired on PBS in November.
Moll has tackled difficult subjects before; Inheritance focused on Monika Hertwig, daughter of Amon Goeth, the ruthless Nazi concentration camp commandant portrayed in Steven Spielberg's Schindler's List. But Moll found Sahara a challenge to film, both logistically and emotionally.
Heat, sandstorms and a difficult border crossing between Niger and Libya took a toll on the runners and film crew, Moll says. In the end, the runners "were determined to finish. That was (what) interested me the most, that drive, that focus ultra marathoners have."
Interactions with African children and families prompted the runners to start H2O Africa, a charitable foundation that has since raised more than $6 million to provide fresh drinking water to Africans. And Engle started Mission Product, a skin-care company for athletes who need sun protection and pain relief.