A competitor takes part in the 31st World Bog Snorkelling Championships, held annually at Llanwrtyd Wells in Wales, Britain August 28, 2016. Entrants must negotiate two lengths of a 60-yard trench through the peat bog in the quickest possible time without using any conventional swimming strokes. (Photo by Rebecca Naden/Reuters)

Young gymnasts practice pull-up on a bar at a gymnasium of a sports school in Jiaxing, Zhejiang province April 11, 2015. (Photo by William Hong/Reuters)

Young girls practice acrobatic skills in the Sichuan Provincial Art School July 14, 2008 in Chengdu of Sichuan Province, China. (Photo by China Photos/Getty Images)

Dancers at the Windmill Theatre in London, England practice a routine wearing gas masks and hard-hats with their costumes, 1940. (Photo by Hulton Archive/Getty Images)

Young contortionists practice at a training school in Ulaanbaatar, Mongolia, July 4, 2016. (Photo by Natalie Thomas/Reuters)

A diving competitor during a practice session at Tokyo Aquatics Centre ahead of the Tokyo 2020 Olympic Games in Japan on Wednesday, July 21, 2021. (Photo by Stefan Wermuth/Reuters)

Indonesian soldiers take part in a handling riots practice ahead of the elections at their military home base in Banda Aceh, Aceh province on April 9, 2019. (Photo by Chaideer Mahyuddin/AFP Photo)

Planes for Team Oracle perform over downtown San Francisco during a practice session for San Francisco Fleet Week October 5, 2007 in San Francisco, California. (Photo by Jed Jacobsohn/Getty Images)