On February 28, Polar explorer Eric Larsen will begin his biggest expedition to date, a less-than-two-month, 500-mile sprint to the North Pole from Canada's Ellesmere Island. Larson, 42, and Ryan Waters, 40, will attempt to traverse the Arctic Ocean unsupported in 49 days, breaking the current speed record set by a Norwegian team in 2006. The duo calls their extreme project "Last North."

"This is easily one of the most difficult expeditions in the world," Larsen, who lives in Boulder, told Men's Journal on the day he left for Northern Ellesmere. "While there have been over 1,500 Mount Everest summits in the past three years, no one has completed a full land-to-North Pole traverse since 2010."

RELATED: The First Expedition to the North Pole

Larsen and Waters will each pull a 350-pound sled packed with food and supplies. Most of the time, they will navigate the frozen Arctic Ocean on cross-country skis outfitted with skins for traction. On extreme ice, they will switch to snowshoes, which are far less efficient, but necessary on dangerously slick terrain.
 
In order to prepare himself for the expedition, Larsen, who also works as a guide in Antarctica, regularly cycles and climbs mountains around Colorado. He and Waters started an expedition-specific training routine last September. Three to four times a week, they do a workout that they've aptly dubbed pulling tires. They hook two large truck tires to their harnesses and hike in the foothills north of Boulder.
 
Larsen estimates each tire weighs between 50 and 60 pounds. "It's not really hard until you're headed uphill trying to pull the tires across rocky, uneven terrain," he says. "It perfectly mimics the Arctic environment, the way the sleds snag on snow and ice chunks and pull you back." On his days off from pulling tires, Larson speed-hikes Mt. Sanitas – Boulder's steepest trail – with a large backpack full of the rocks.

"We do a lot of physical training," Larsen says, "But really, it's just to calm our minds. On an expedition of this caliber, it's ultimately about the mental game."