MURRAY — It's part road bike, part mountain bike and part steeplechase.

And it's exploding in popularity.

It's cyclocross, and it is becoming one of the fastest-growing sports in the bicycle world.

"I love it," said Jeff Clawson, a local cycling promoter and club organizer with Canyon Bicycles in Draper. "It's a sport where a beginner right up to a pro can come and race and have a great time. They can bring the family and they can see you on every lap."

This weekend at the Weber County Fairgrounds, the Utah Cyclocross Series will hold its state championship races. And, if recent competitions are any indicator, there will be upwards of 300 participants in the various classifications.

Last weekend, for example, there were more than 300 entrants in the weekly races at Wheeler Farm on Saturday and a few dozen more on Sunday at a race in West Valley City.

And while those coming to race are falling in love with the sport, many have little idea it exists or why it is so popular.

The sport has been around for more than a century with the first known race held in Europe in 1902. It is said to have developed as a form of competition for road cyclists to participate in during the fall and winter months when weather conditions prevented racing and training on slick roads.

Embracing the conditions, cyclists raced their bikes across fields, hillsides, through groves of trees and across fences for fun and for training purposes. Slowly, the sport took off and is now hugely popular in Europe while also gaining considerable traction in the U.S.

In fact, Lance Armstrong helped kick off his return to competitive cycling by lining up for a cyclocross race in Las Vegas shortly after he announced his comeback.

"It's a great spectating sport," Theresa Carr, a frequent participant in the races, said. "People can get around the whole course and see what's going on. I think it has more of a grass roots feel than even mountain biking. There's just more of a community feel to it."

The bikes used often have a road bike frame, but usually come with thick, studded tires ideal for off-road conditions. Even the components are usually scaled down to make the bikes more simple to ride and easier to handle.

Each cyclocross race is different. Depending on the terrain and the event promoter, the course is built each week with unique twists, turns, climbs and obstacles. And if the weather throws some ice or rain at the competitors, they're usually a little happier.

Courses typically require riders to cover multiple laps, and in most cases the riders must dismount their bicycles several times to climb steep hills, jump logs or hurdles or cross streambeds.