An American man made history last week after becoming the first person to cross Antarctica alone and unaided.

Colin O'Brady, a 33-year-old Portland native, lugged a nearly 400-pound sled laden with supplies across over 900 miles of brutal Antarctic terrain in 54 days. British Army Captain Louis Rudd completed the same journey, also unaided, two days later.

Nancy Koehn, professor at the Harvard Business School and author of "Forged In Crisis," explained the demanding terms of the journey on Boston Public Radio Wednesday.

"Both of these gentlemen were determined to do this 'unaided' and 'unsupported,' meaning without any power but [their] own power, and unsupported, [meaning] there would be no resupply," Koehn explained.

"You've got to carry all your food," she continued. "That's why the pulk [sleds] each weighed between 300-375 pounds when they started out. Most of that is food, some white gas to power the little stoves they're going to use to melt ice or snow for water, an extra pair of skis in the case of Louis Rudd, and a tent."

Adding to the physical challenges of the journey are the psychological ones, Koehn added. O'Brady, for example, prepared for the long days alone by going on silent meditation retreats where even making eye contact with another person was forbidden.

"The interesting thing here is how each of these gentlemen have spoken ... about what it means to live with your fear and only yourself," Koehn said.

"They are alone and doing this, dealing with their mental demons ... That is a really interesting existential psychological self-awareness issue that these case studies will have something to say about for a long, long time," she continued.