Athletes vie for the ball during the Mud Olympics in Brunsbuettel, Germany, 30 July 2016. Since 2004, amateur athletes have been competing in various events at the mouth of the Elbe river on the North Sea. The proceeds are traditionally donated to the Schleswig-Holstein Cancer Society. (Photo by Daniel Bockwoldt/EPA)

A sculpture is displayed at the Olympic Sculptures Exhibition at the Sculpture Park September 4, 2006 in Changchun of Jilin Province, China. (Photo by China Photos/Getty Images)

In this handout image provided by Red Bull, Artem Silchenko of Russia dives from the 27 metre platform at training on Hong Island in the Andaman Sea during the final stop of the 2013 Red Bull Cliff Diving World Series on October 25, 2013 at Krabi, Thailand. (Photo by Romina Amato/Red Bull via Getty Images)

2016 Rio Olympics, Gymnastics training, Rio Olympic Arena, Rio de Janeiro, Brazil on August 4, 2016. Close up of the feet of Rebecca Downie (GBR) of United Kingdom as she trains on the beam. (Photo by Dylan Martinez/Reuters)

A Maasai moran athlete has his face smeared with red ocher paint during preparations for the 2016 Maasai Olympics at the Sidai Oleng Wildlife Sanctuary, at the base of Mt. Kilimanjaro, near the Kenya-Tanzania border in Kimana, Kajiado, Kenya December 10, 2016. (Photo by Thomas Mukoya/Reuters)

A reveller from Uniao da Ilha samba school performs during the second night of the carnival parade at the Sambadrome in Rio de Janeiro, Brazil February 27, 2017. (Photo by Pilar Olivares/Reuters)

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.

Japan' s Kaori Sakamoto competes in the women' s single skating short program of the figure skating event during the Pyeongchang 2018 Winter Olympic Games at the Gangneung Ice Arena in Gangneung on February 21, 2018. (Photo by John Sibley/Reuters)