IN THE WESTERN DESERT, Egypt -- Three ultra-endurance

athletes have just done something most would consider insane: They

ran the equivalent of two marathons a day for 111 days to become

the first modern runners to cross the Sahara Desert's grueling

4,000 miles.

"This has been a life-changing event."

-- American runner Charlie Engle

"It will take time to sink in ... but this is an absolutely

once in a lifetime thing. They say ignorance is bliss, and now

that I know how hard this is, I would never consider crossing the

Sahara on foot again," said American runner Charlie Engle, 44,

hours after he and the others completed the run at Egypt's Red Sea.

Engle said he, Canadian Ray Zahab, 38, and Kevin Lin, 30, of

Taiwan, ran the final stretch of their journey that took them

through the Giza pyramids and Cairo to the mouth of Suez Canal on

four hours of sleep. Once they hit the Red Sea, they put their

hands in the water to signify crossing the finish line.

"We touched the water in Senegal at the beginning, and we

touched the water in the Red Sea at the end. They were the bookends

of our journey," Engle, of Greensboro, North Carolina, said on the

telephone from a hotel room in Cairo.

In less than four months, they have run across the world's

largest desert, through six countries -- Senegal, Mauritania, Mali,

Niger, Libya and finally Egypt.

A film crew followed them, chronicling the desert journey for

actor Matt Damon's production company, LivePlanet. Damon plans to

narrate the "Running the Sahara" documentary.

The trek is one of extremes. The relentless sun can push

temperatures above 100 degrees Fahrenheit during the day, but at

night it sometimes dips below freezing. Strong winds can abruptly

send sand swooping in every direction, making it difficult to see

and breathe.

Running through turbulent conditions is nothing new for these

athletes who have traveled the world competing in adventure races.

But they say nothing has tested their physical and mental

limitations like the Sahara.

American Charlie Engle (right) and Canadian Ray Zahab did the unthinkable and crossed the Sahara Desert in 111 days. AP Photo/Nasser Nasser)

Throughout the run, the runners have been stricken with

tendinitis, severe diarrhea, cramping and knee injuries all while

running through the intense heat and wind -- often without a paved

road in sight.

"This has been a life-changing event," Engle said.

The runners say they undertook the challenge to see if they

could accomplish something that many have called impossible. They

use GPS devices to track their route and teamed up with local

experts and a host of sports professionals who also followed them,

along with the documentary crew, in four-wheel drive vehicles.

Typically, the three began each day with a 4 a.m. wake-up call.

About an hour later, they started running. Around noon, they took a

lunch break at a makeshift camp, devouring pasta, tuna and

vegetables. A short nap on thin mattresses in a yellow-domed tent

usually followed before they headed out on the second leg of their

day's run.

Finally, around 9:30 p.m., they called it quits each day,

returning to camp for a protein and carbohydrate-packed dinner

before passing out for the night.

Despite the preparation and drive to finish, the runners said

they often questioned -- mostly to themselves -- what they were

doing. Zahab described stopping one recent day for a bathroom break

only to discover the wind was blowing so harshly that he couldn't

keep the sand out of his clothes. "And I thought to myself, 'What

the hell am I doing?"' he said.

But Zahab kept going, as did the other two, never skipping a

day. Most days the three ran a total of 44 to 50 miles -- sometimes

a little more, sometimes a little less.

They were interviewed by The Associated Press on Saturday -- day

108 -- on the side of a road about 112 miles from Cairo in Egypt's

harsh Western Desert, part of the greater Sahara.

At several points in their trek, the athletes stopped near

sparsely populated wells to talk with villagers and nomads about

the difficulties they face finding water. That marked another goal

of the run -- raising awareness for the clean water nonprofit group

H2O Africa.

"We have seen firsthand the need for clean water, which we take

for granted in North America. It's such a foundation for any

community," Zahab said during day 108's lunch break. The three

plan to fund-raise for the group after they return home and finish

recuperating.

"It started off as a huge motivator, especially as we passed

through countries where the water wasn't clean," Engle said.

But as the trio's bodies became more depleted, the focus was

"the day-to-day battle to stay alive and keep moving," he said.