Hobby-horsing may be the most popular sport you've never heard of.

Hobby-horsing has taken Finland by storm, amassing a sizable following among young Finnish girls between the ages of 10 and 18. The sport involves many of the aspects of actual horse competitions, such as show jumping and dressage (in which horse and rider have to perform a series of complicated, premeditated movements and jumps). In hobby-horsing, the rider recreates these equestrian competitions while riding a stick with a fabric horse head glued on top.

Some scoff at hobby-horsing, saying that it's unusual or childish, but for the girls who participate, it holds serious value. "Hobby-horsing has a strong therapeutic side to it," Alisa Aarniomaki, a former hobbyhorse competitor and enthusiast, told the Associated Press. "I've gone through lots of trouble and I'm still struggling with some issues. It has helped me a great deal that I can occasionally just go galloping into the woods with my friends. It somehow balances my mind." Aarniomaki has organized parades in Helsinki, where she and her friends march through the city with their hobbyhorses. She says hobby-horsing has become a symbol of female empowerment.

The sport requires athleticism, coordination and poise, since, after all, the riders themselves are doing the jumping instead of the horses. The hobbyhorses that the riders use in competition are often handmade, complete with glued-on hair and eyes. They are given proper names. They're exchanged and sold by owners at events and through social media, some for hundreds of dollars.

Though the sport thrives on the internet and social media, volunteers organize regional competitions throughout Finland over the course of the year. The events culminate in the National Finnish Hobby Horse Championship Games, which took place in Vantaa in April. The competition, which eschews strict rules and doesn't have an official governing body, consisted of about 200 participants and over 1,000 spectators. Judges look at things like how long a rider's strides are, how high they jump, how fast they complete the course, style and posture. You can see all this in action in the video below.

A cultural phenomenon

Finnish filmmaker Selma Vilhunen first saw a hobby-horsing event five years ago, after a friend sent her a YouTube video. She admits that she laughed at first but was also fascinated at the intensity of the sport. She continued to do research and eventually made a documentary, which came out just before the national competition, called "Hobbyhorse Revolution." The film follows Aarniomaki and two other girls, Elsa Salo and Mariam (Aisku) Njie. A major theme of the documentary is overcoming the stigma that many of the girls who participate in the sport experience. The documentary explores their participation in the sport while dealing with struggles at school and at home.

Since the film hit the festival circuit and a slew of media outlets covered the national competition, hobby-horsing has become more mainstream in the United States. At the start of July, the Tryon International equestrian center in Mill Spring, North Carolina, will host its first hobby-horsing competition.

The equestrian world supports and encourages the sport. "We think it's simply wonderful that hobby-horsing has become a phenomenon and so popular," Fred Sundwall, the secretary general of the Equestrian Federation of Finland, told the AP.

So popular that about 10,000 people in Finland currently participate in the sport. It seems this horseplay is anything but.