Competitors wearing masks take part in the “Naked Running”in Yinchuan, Ningxia Hui Autonomous Region, on Jan. 9, 2015. This competition drew nearly 100 players, in vests and shorts, to run around the Bei Ta lake of over 4,000 km. (Source: Xinhuanet)

Competitors take part in the “Naked Running”in Yinchuan, Ningxia Hui Autonomous Region, on Jan. 9, 2015. This competition drew nearly 100 players, in vests and shorts, to run around the Bei Ta lake of over 4,000 km. (Source: Xinhuanet)

A competitor  takes part in the “Naked Running”in Yinchuan, Ningxia Hui Autonomous Region, on Jan. 9, 2015. This competition drew nearly 100 players, in vests and shorts, to run around the Bei Ta lake of over 4,000 km. (Source: Xinhuanet)