A mouse rides on the back of a frog in floodwaters in the northern Indian city Lucknow June 30, 2006. (Photo by Pawan Kumar/Reuters)

Opossums on their mothers back at a game reserve in Central Minnesota, USA, on September 2, 2013. (Photo by Caters News Agency)

Greyhounds with stuffed and sprung model monkeys strapped to their backs before a hurdle race at Wellinborough. (Photo by E. Bacon). 21st April 1928

A woman leaves sauna during the sauna marathon in Otepaa, Estonia on February 2, 2019. Participants have to track down, locate and visit designated saunas in the Otepaa area as fast as possible during the event. The team that completed all of the saunas in the shortest time wins. (Photo by Ints Kalnins/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.

A man sits at the back of his car in the city centre of Yangon on September 15, 2023. (Photo by Sai Aung Main/AFP Photo)

A Pakistani labourer carries bricks on his back at a construction site at a residential area in Islamabad on March 29, 2017. (Photo by Aamir Qureshi/AFP Photo)