Shane Skowron makes his way toward Highway 332 about two hours into the Arrowhead 135 Monday, January 27, 2014 near International Falls, Minn. Derek Montgomery/For MPR News

International Falls, Minn. -- For most mortals, running, biking or skiing in a 135 mile race through Minnesota's north woods would seem a daunting enough task. But in the Arrowhead 135 Ultra, which started Monday in International Falls, the competitors not only brave sub-zero degree temperatures, they crave it because it's part of the allure of the race -- one of the toughest in the world. Starting in International Falls, the race follows the Arrowhead State Snowmobile Trail to Tower. This year, there were 141 starters and the official air temperature at the start was 24 degrees below zero. Here's what the endeavor looked like.

• Arrowhead 135: The story behind the photos

UPDATE (Jan. 29): Jay Petervary of Idaho won the race, crossing the finish line by bike early Tuesday morning. It took him 20 hours and 11 minutes to complete the course. His wife, Tracey Petervary, was the first woman to finish the race. She crossed the finish line about seven hours after Jay.

The first runner to cross the finish line was Scott Hoberg of Minnesota (seen in the 10th photo below). He completed the course in 43 hours and 26 minutes. Alicia Hudelson of Georgia was the first woman runner to finish the race. Her time of 47 hours and 59 minutes beat the current record holder by seven hours. Full results here.