Xie Jun and his wife, Qi Yingju, both finish the Berlin Marathon in 2015. Provided to China Daily

Using Crowdrise, a crowdfunding website, he raised $6,030－18 percent more than his target sum－for the Blue Sky Lab campaign run by Friends of Nature, one of the oldest environmental NGOs in China. The program purchases materials and teaches students from low-income families in Beijing to assemble do-it-yourself air filters. The money Li raised is expected to benefit 177 families.

"I abuse myself by running in extreme subzero temperatures in the North Pole and you donate to help the kids in China breathe cleaner air at home," he wrote on his Crowdrise page.

Li and a female compatriot, Fan Beibei, were among about 50 runners from 20 countries who braved temperatures as low as -40 C to complete the 42-km event, which was postponed several times due to cracks in the ice. Armed guards stood watch during the race to protect runners from the threat of polar bears.

Li is also one of a small but growing group of Chinese who have completed marathons on every continent, including Antarctica.

Despite the current enthusiasm, the Chinese have shown themselves to be somewhat fickle in terms of their motivation for traveling abroad.

A few years ago, sports league-themed tourism prevailed, Du says. "Then, it was outdoors, and now it's running. Many runners are actually traveling in the name of running marathons."