Marathons, triathlons and ultramarathons test human endurance and strength to the limit. For runners of such races who are still not satisfied and want an even more challenging competition, they can try the Man vs. Horse Marathon (MHM) in Wales, United Kingdom.

This year’s MHM will be held in Llanwrtyd Wells on 14 June, with a distance of 35.4 kilometers and elevation of 1,372 meters.

As the name implies, the contest pits human runners against horses with riders. Of course, horses win 90 percent of the time, though a man won last year’s contest. The 2024 winner, Daniel Connolly, became the fourth human to beat a horse, finishing the race in 2 hours, 24 minutes, and 38 seconds, nearly 10 minutes ahead of the first horse, DNS Ronaldo, which was ridden by Kate Atkinson, Run Republic reports.

The first human to beat a horse in the MHM was Huw Lobb, who pulled it off in 2004, according to Run Republic.

Another unique race that was less strenuous than the MHM was held in Los Angeles, California on 25 April.

Exclusively for men, the race was invented and organized by 17-year-old high schooler Eric Zhu.

The race track was a two millimeter-long pipette while the racers were so tiny they had to be magnified 100 times through a microscope, Agence France-Presse (AFP) reports.

The microscopic scene was recorded with a camera and the video was transferred to a 3D animation software before being broadcast to the audience.

It was a brief race with the loser highlighted instead of the winner. The racers were sperm cells of the male contestants. The semen were collected earlier for filming.

A YouTube livestream of the contest attracted over 100,000 views, according to AFP.

Zhu said he raised $1 million to organize the motility — or ability of sperm to move — race to promote reproductive health, specifically sperm count.

He was concerned about social media posts that said the average sperm count had decreased by half over the past 50 years, and fears “there could be this dystopian future where no one will be able to make babies,” AFP reports.