Colin O'Brady is a professional endurance athlete, a motivational speaker, a world record holder and, now, the first person in history to cross the continent of Antarctica alone and without wind assistance.

The 33-year-old Portland native set out on a brutal 921-mile journey across Antarctica in early November. He was alone and unassisted, dragging a sled weighing hundreds of pounds that contained everything he needed to stay alive in some of the harshest conditions on earth.

THANKS TO OUR SPONSOR: Become a Sponsor

After 54 days, O'Brady succeeded Wednesday.

Just days before he reached the finish line, OPB’s "All Things Considered" host Kate Davidson checked in with O’Brady at the end of a very long day.

“I managed to go 33.1 miles [today],” O’Brady said. “It was actually the longest day of my entire expedition.”

He went on to break his own personal best, trekking nearly 80 miles in his final sprint to the finish that began on Christmas Day.

THANKS TO OUR SPONSOR: Become a Sponsor

O'Brady has been documenting his journey on his Instagram, keeping his followers updated on both the highs and lows of the adventure. He said one of the hardest parts of the experience is that it seemed to never end.

“There are no breaks, there’s no days off,” O’Brady said. “It’s just been a continual challenge that has pushed me and all my limits to its absolute extreme.”

But there was also a practical reason why O’Brady couldn’t take a day to rest.

“I haven’t taken a single day off in 50 days because if I do I’ll run out of food,” he told OPB.

O’Brady wasn’t just in a personal race against the clock. He was trying to beat a fellow adventurer, British Army Capt. Louis Rudd, who landed with him in Antarctica.

Before he set out, O'Brady dubbed the adventure "The Impossible First" because many people had told him it would be impossible.

“I wanna prove that it’s not impossible,” O’Brady said. “Not just for myself but for others who are daring to dream greatly in their own lives.”

Use the audio player below to hear the entire conversation with Colin O’Brady.

Your browser does not support the audio element.