CAIRO, Egypt. Imagine traveling across a 4,000-mile-wide (6,437.4-kilometer) desert with little water nearby. Now, imagine running across that same desert, at least 44 miles (70.8 kilometers) at a time, day after day. That's just what three men did recently. They became the first modern runners to cross the Sahara Desert. Describe the men's journey across Africa. What challenges did the men face? Where did their journey take them? Use information from the lesson in your answer.

Charlie Engle of the U. S., Ray Zahab of Canada, and Kevin Lin of Taiwan completed the run in 111 days. They traveled through six countries. Starting in Senegal, they ran through Mauritania, Mali, Niger, Libya, and Egypt. After nearly four months, they reached Egypt's Red Sea. There, they put their hands in the water to show that they had crossed 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," said Engle. He added, "It will take time to sink in . . . but this is an absolutely once-in-a-lifetime thing. . . . [Now] that I know how hard this is, I would never consider crossing the Sahara on foot again."

Most people would never have considered such a journey in the first place. The Sahara Desert is one of the harshest places on Earth. During the day, the sun can send temperatures soaring above 100 degrees (over 37 degrees Celsius). Nighttime temperatures can dip below freezing. Strong winds send sand flying in every direction, making it difficult to see and breathe.

Engle, Zahab, and Lin are all experienced athletes. They have run in adventure races around the world. Still, nothing would have prepared them for the Sahara. At various times during the run, they suffered from upset stomachs, cramping, and knee injuries. At the same time, they had to endure the unforgiving climate.

The runners' days were exhausting, too. After waking up at 4 a. m., the trio would begin running at about five. Around noon, they would take a lunch break, eating pasta, tuna, and vegetables—all foods that provide energy. After a short nap in a tent on thin mattresses, they would start running again. They would run until about 9:30 p. m.

The runners brought along supplies and equipment to protect themselves from the dangers of the desert. They had devices that used the global positioning system to track their route. They also teamed up with local experts and sports trainers. These people followed the runners in four-wheel-drive vehicles.

Despite the planning and preparation, the runners often questioned whether they were doing the right thing. Sometimes the wind was so harsh that the runners could not keep the sand out of their clothes. The three kept going, however. They ran up to 50 miles (80.5 kilometers) a day. That's twice the length of a city marathon.

A film crew also followed the runners. The crew was recording the journey for actor Matt Damon's movie company. Damon will make a movie about the trip called "Running the Sahara."

Why did the athletes make the run? They welcomed the challenge. They also wanted to raise awareness about an ongoing problem. Desert communities often struggle to find clean water. Several times, the athletes stopped near wells to talk with villagers about the situation.

"It started off as a huge motivator, especially as we passed through countries where the water wasn't clean," Engle said. He and the other runners hope that their work will help the efforts of H2O Africa. The group helps countries find or make clean water. The athletes plan to raise money for the group.

"We have seen firsthand the need for clean water, which we take for granted in North America," Zahab said.

The desert run was full of challenges. Now that the runners have finished, the men know that they will never be the same.

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

The Associated Press contributed to this story.