Hobbyhorsing is a hobby created entirely by girls in Finland, without any input and often with active discouragement from adults. The hobbyists have made an entire world of hobbyhorsing with competitions, training camps and even nationals with hundreds of participants and thousands of spectators. Even though they are often met with derision from outsiders, this is their thing and they keep at it, regardless of what everyone else thinks. In fact, some of them see no reason to stop once they grow up. The oldest hobbyists are now in their twenties. 

(video source)