The Badwater Ultramarathon follows a 135-mile route through California, from the bottom of Death Valley to the Sierra Nevadas.

Runners start on Badwater Road — a two-lane road tucked into eastern edge of the valley — and head north.

They run along the bed of the valley for 40 miles before curling west, where they face three mountain ascents and a 95-mile, 18-hour trip to Mt. Whitney, the highest peak in the contiguous United States.

Carlos Sá began his race at 10 a.m. on the morning of July 15.

In the hottest place on Earth, a heat wave struck. During the six hours it took him to reach the last checkpoint in the deep basin of Death Valley (named, perfectly, "Furnace Creek"), temperatures reached 109 degrees and the strongest desert wind gusts blew at 32 miles per hour.

REUTERS/Lucy Nicholson Mile 31 — in the thick of the heat and wind of the valley, but still early in the race — was the hardest of them all, Sá says.

He has preferences when it comes to distance running. Although he once ran an ultramarathon through the Sahara, extreme temperatures don't do much for him.

He says he likes mountain running the most.

"The distances and the mountain, the unevenness of the ground, or the boldness of always going further is what appeals to me in these distances," he says.

In the end, it took him 24 hours and 38 minutes to reach the finish line, fast enough to win the race by a full 15 minutes.

Here's the route:

Google Maps

Running 135 miles non-stop through desert and mountains in under 25 hours is an unfathomable feat. You can understand what it's like to run two miles, five miles, ten miles, maybe even 24 miles. But 30 miles? 88 miles? 105 miles, with 30 miles to go?

There is no unifying theory of what makes people become ultramarathoners. The reasons are individual.

Sá, remarkably, started running for the same reason millions of people start running — to get in shape.

Seven years ago, at age 32, Sá weighed 211 pounds and admits he smoked two packs of cigarettes a day. He used to worked in the textile industry before the factories of northern Portugal closed, and then spent some time as a window washer.

That year he decided to, in his words, turn his life around. He always ran as a kid, so he picked it back up as an adult.

"I started running again to feel better, physically, and also to find a new path in my life, a healthier one," he said. "But I got so passionate that I decided then to start testing my limits, and that is my goal, to see how far can I go with quality."

Here is a picture of him then:

Courtesy of Carlos Sa

And here he is now, 66 pounds lighter and a world-class athlete:

David McNew/Getty Images

David McNew/Getty Images

Today Sá is 39-years old and lives in Barcelos, Portugal with his wife and two young children. He is a professional ultramarathon runner with Berg Outdoor as a sponsor.

Everyone starts running to change themselves, to lose a few pounds or to have a more active lifestyle or because they were inspired by a magazine. The choice to start running is the choice to change, at least in some small way.

Sá took that to the extreme. He made the choice to see how much he could run, and changed the trajectory of his life in the process.

He has never run a road marathon, and doesn't plan to. He is only interested in distances and mountains, in seeing exactly how far he can go.

"I see all races through me," he says, "as something I do to challenge myself and go even further."