When the National Interscholastic Cycling Association, or NICA, was founded in 2009 to help high school mountain bike teams across the country get up and running, no one knew what a phenomenon it would become. The number of Americans riding bikes decreased by 8 percent between 2000 and 2010; and for kids ages 7 to 17, the decline was a precipitous 21 percent. The sport of mountain biking, too, had been struggling to grow, never quite regaining its mid-1990s glory.

Today NICA is one of cycling’s greatest success stories. There are high school cycling leagues in 18 states, some of which—such as Utah and Minnesota—are expanding so fast they can hardly accommodate all the racers on the courses. In 2015, we embedded with two schools in Minnesota to find out how a new generation of high school mountain bikers is transforming the sport. Once you see them in action, it’s impossible not to get stoked about what’s next.

“It has been explosive,” says NICA’s executive director, Austin McInerny. “We grew 43 percent from 2015 to 2016. Some of the leagues are seeing more in the 7th- and 8th-grade fields than in the older ones. I’m calling that the tip of the iceberg. I think it could grow even quicker if we found more adults who wanted to step up and run those teams.”

John Emery is the manager of Michael’s Cycles in Chaska, Minnesota, where the local high school team has been doubling in size every year (it’s now up to 40-plus members). “NICA is just bonkers,” he says. “The number of new people getting on bikes for the first time in their lives, it’s just huge. I’ve never seen anything like it.”

And not all of those new riders are kids. “Once the kids get involved, the parents get enthusiastic about mountain biking as well,” says Erik Saltvold, owner of Erik’s Bike, Board, and Ski, which has 24 locations in Wisconsin and Minnesota. “It brings whole families into the sport.”

There are challenges. Programs rely on volunteer coaches, who can be hard to secure. And there’s no getting around the fact that the sport is expensive (NICA estimates the cost of a season per student at between $1,275 and $2,275, depending on the price of the bike), although the leagues offer scholarships and some have loaner-bike programs. And while it’s growing fast—by 2020, NICA expects to have 18,000 student athletes—it’s small compared with more established sports such as football and cross-country, which had about 1.1 million and 480,000 athletes, respectively, in the 2015-16 season. But it’s impressive that NICA continues to pick up recruits even as some traditional sports programs are showing signs of attrition: Since 2009, the year NICA started, Minnesota’s high school football programs alone have lost more than 2,200 athletes.

“A lot of these kids have done football, baseball, and haven’t really found their place in traditional sports,” says Shaun Anderson, who coaches the Cuyuna Lakes team in northern Minnesota. “They find this and it’s given them a home.”

McInerny says that what’s happening in Minnesota is a snapshot of what NICA is experiencing in most of its programs. And that bodes well for cycling’s future: NICA’s own survey found that 99.7 percent of its riders consider themselves lifelong cyclists. We asked one rider, Madonna Moua, of Patrick Henry High School, if she’d miss racing after graduation. She thought about it, looked up at the hill, and said, “No. I’m going to go to college somewhere with a lot of mountains.”