Kaitlin Hawayek and Jean-Luc Baker perform during the short dance program at the U.S. Figure Skating Championships in Greensboro, N.C., Friday, Jan. 23, 2015. (AP Photo/Chuck Burton)

Skeleton involves a person riding a small sled down a frozen track while lying face down. The sport is a more intense form of luge because skeleton competitors leap onto the sled and slide downhill head first. Skeleton athletes can reach up to 80 mph on straightaways, causing forces up to 5g, so the helmet is a critical component for attitude as well as safety.

Students exercise in body training at Bishan Vocational Education Center in Chongqing, southwest China, January 13, 2016. These students were trained to be stewardesses of the high-speed train. (Photo by Xie Jie/Xinhua)

This undated handout photograph released by Taipei City Zoo on July 17, 2013 shows recently born panda cub of giant panda Yuan Yuan in an incubator at Taipei Zoo in Taipei. (Photo by AFP Photo/Taipei City Zoo)

Peruvian surfer Domingo Pianezzi rides a wave with his alpaca Pisco at San Bartolo beach in Lima March 16, 2010. Pianezzi has spent a decade training dogs to ride the nose of his board when he catches waves, and now he is the first to do so with an alpaca. (Photo by Pilar Olivares/Reuters)

Public Space series, 2015. This series by Morteza Niknahad and Behnam Zakeri tends toward cinema, taking an almost cartoonish view of modern life in Iran. This work was inspired by the social life of dolphins. (Photo by Morteza Niknahad and Behnam Zakeri/The Guardian)

The disused bobsled track from the Sarajevo 1984 Winter Olympics is seen on Mount Trebevic, near Sarajevo, September 19, 2013. Abandoned and left to crumble into oblivion, most of the 1984 Winter Olympic venues in Bosnia's capital Sarajevo have been reduced to rubble by neglect as much as the 1990s conflict that tore apart the former Yugoslavia. (Photo by Dado Ruvic/Reuters)

A woman tries to protect her daughter as refugees scuffle with the Greek police in their effort to reach the borderline with Macedonia, near the Greek village of Idomeni, Sunday, November 22, 2015. Over 1,000 migrants gathered in the Greek town Idomeni protested Saturday against the decision by Macedonian authorities across the border to turn away migrants who are not from war zones such as Syria, Afghanistan and Iraq. (Photo by Giannis Papanikos/AP Photo)