A participant of the Wild Sau Dirt Run 2015 passes a mud barrier in Obertriesting, Lower Austria, Austria, Saturday, April 4, 2015. The Wild Sau Dirt Run is a cross country and steeplechase race for men and women over the distances of 5, 10 and 20 kilometers (3.1, 6.2 and 12.4 miles). (Photo by Ronald Zak/AP Photo)

A man takes pictures at the finish line during the Colour Run at Centennial Park in Sydney August 25, 2013. According to organizers, 15,000 runners registered to complete the 5km (3 miles) course in Centennial Park on Sunday, being covered in blue, pink, orange and yellow powder on their way to the finish line. (Photo by Daniel Munoz/Reuters)

A new volunteer for the Ukrainian interior ministry's “Azov” battalion takes part in tests before heading to frontlines in eastern Ukraine, at the battalion's training centre in Kiev, Ukraine, August 14, 2015. (Photo by Gleb Garanich/Reuters)

Women practice swimming with mermaid tails at AquaMermaid swimming school, a mermaid training school in Chicago, United States on March 19, 2017. Participants are fulfilling their lifelong ambitions of becoming mermaids with a new type of fitness mermaid swimming. (Photo by Bilgin S. Amaz/Anadolu Agency/Getty Images)

Brides-to-be participate in the "Running of the Brides" race in a park in Bangkok November 28, 2015. A hundred husbands and wives-to-be wore their wedding dresses and running shoes and competed in an event for a combined prize worth 1 million Thai baht ($27,928), according to the organisers. (Photo by Athit Perawongmetha/Reuters)

A view of the scene of a train accident after two commuter trains collided head-on near the town of Andria, in the southern region of Puglia, killing several people, Tuesday, July 12, 2016. (Photo by Luca Turi/ANSA via AP Photo)

Sergey, one of the participants of PARTISAN courses, poses for a portrait in an abandoned building in Olgino, St. Petersburg, Russia on November 23, 2016. Sergey came to St. Petersburg from the city of Cheliabinsk to attend an intensive seven-day program. Sergey is a businessman, a traveller and a blogger. His another passion are “men's hobbies”, that's why he participated in the paramilitary courses. (Photo by Alexander Aksakov/The Washington Post)

A participant sets off on a penny-farthing bicycle at the start of the The Tweed Run in central London, Britain, May 14, 2016. The Tweed Run, a very British public bicycle ride through London's streets, with a prerequisite that participants are dressed in their best tweed cycling attire. (Photo by Hannah McKay/Reuters)