KANSAS CITY, Mo. (AP) — Katie Compton always loved playing in the mud.

As a little girl, she'd come home from an afternoon of playing with her friends, and her mother would be standing in the doorway shaking her head. Compton would be covered in filth, from the top of her head to the tips of her toes, with a smile always on her face.

"I think that's part of why I love cyclocross," Compton said. "It's like you're a kid when you're playing in the mud, and you come home and your mom is like, 'What the hell is wrong with you?' And you're like, 'It's fun! You should try it!'"

These days, thousands of cyclists are heeding her advice.

Popular for decades in northern European countries such as Belgium and Denmark, cyclocross has finally caught fire in the United States. The combination of road racing and mountain biking is drawing record numbers of riders to events all over the country, from elite competitors such as Compton to those just learning to pedal a bike.

"I don't know how many riders there were when I started," said Compton, who picked up the sport in the late 1990s and recently won her 10th consecutive national championship.

"I know it's quadrupled, minimum," she said. "Everything has gotten so big."

If anybody could appreciate cyclocross's explosive growth, Compton might be it. A tree-time world silver medalist, Compton is also a two-time World Cup champion. She finished ninth at the world championships Saturday in Hoogerheide, Netherlands.

Marianne Vos of the Netherlands successfully defended her world title.

The discipline of cyclocross was born in the early 1900s as a way for European road cyclists to stay in shape during the harsh winter months, but it started to grow in popularity during the 1950s as its own sport. In the last couple of decades, high-profile European races often draw more than 20,000 fans, and television ratings rival that of the NFL in the U.S.

It hasn't been nearly as quick to catch on in America.

Road cyclists and mountain bikers balked at the idea of having to dismount and carry their bikes over obstacles — one of the major components of a cyclocross race, which generally last about an hour. And the thought of racing over mile-long, man-made courses built in muddy farm fields or tightly contained urban parks wasn't all that attractive.

"It's not technically a snow sport, so that keeps it away from getting Olympic attention," Compton said, "but I do think road racers enjoy cyclocross because it's more technical and shorter, and you don't have as much time to daydream, and mountain bikers like it because it's half the duration and slightly safer. It's a good combination."

Then there's the weather: The season adheres to the sport's roots by beginning in autumn and running through the winter, resulting in conditions that can be, well, challenging.

"It doesn't appeal to every racer," said cyclocross rider Matt Shriver, who works for bike manufacturer Trek. "But the hardest conditions where you suffer the most are the ones you really remember. And when you're doing it, you're on the starting line and freezing to death, it's not fun. But when you're in the mud, crashing, yeah, it's actually really fun."

In other words, people who give it a chance often become hooked.

About 32,000 riders started one of the USA Cycling's cyclocross events in 2005; that number rose to more than 110,000 by 2012. And the number of participants at the national championships in Boulder, Colo., earlier this month was up nearly 30 percent over a year ago.

"It's sort of following a trend of cycling increasing in popularity," said Marc Gullickson, who heads USA Cycling's cyclocross effort. "The lifestyle and atmosphere at these events is pretty fun. It's sort of a tribal atmosphere. Hardship generally brings people together."

Unlike road cycling or mountain biking, where recreational riding is common, cyclocross is all about competition. Races are what counts. But that doesn't mean everyone participating will invest in a $10,000 bike, or even take their fitness all that seriously.

After all, the race is only part of the race weekend.

"It really starts with the party atmosphere," said Cyclocross Magazine founder Andrew Yee, "and then it goes viral. You bring your friends, they watch and they want to try."

Yee said the sport's growth is most evident in the number of races that have popped up, particularly in places that had previously been a cyclocross wasteland. USA Cycling awarded the 2015 national championships to Austin, Texas, where the culture only recently took hold.

"We've been seeing hotbeds across the country achieve double-digit growth year over year," Yee said, "but also tremendous growth in other places. Ten years ago, it was in New England and maybe California. Now, you have scenes in places like Chicago."

It's enough to make riders such as Gullickson, who got their start with cyclocross when the sport was still considered a novelty, shake their heads in amazement.

"If you're a cycling enthusiast or you like riding your bike in the summer, it's sort of another place to put your effort or enthusiasm," he said. "Plus, it sort of gives everyone an excuse to go out and play in the mud."