Runners hit the streets for the 35th annual Chicago Marathon in 2012. (Brad Hagan / Flickr)

This week's primary isn't the only race in town. Amateur runners can apply for a spot in the 39th annual Chicago Marathon starting at 10 a.m. Tuesday.

A marathon last month in Antarctica was the first of seven on seven continents ... in seven days. Two of the competitors are back in Chicago to tell the story–including the winner.