If you go

What: Go Pro Mountain Games

When: June 6-9, various events all weekend

Where: Vail

More info: http://mountaingames.com/

Check out Justin Wagers on YouTube: http://youtube.com/user/jwage23?feature=watch

Two years ago, Ken Wagers gave his two sons Justin and Chris a Christmas gift that would change their lives -- a two-inch wide stretch of elastic material.

Justin Wagers, who recently graduated from Boulder's Fairview High, remembers thinking his father had lost it.

"I thought it was ridiculous at first," Justin Wager said of the gift, a slackline.

It sat in the box for three months or so, but now Dad is getting the last laugh. This week, now-professional slackliner Justin Wagers, 18, heads to the Go Pro Mountain Games to compete in the 2013 Slackline World Championships. Younger brother Chris Wagers, 15, will also compete in Vail, in the amateur division.

They still have that first line, a black and yellow "jib line," Chris Wagers says, but it's been retired from too much use.

Chris admits that when the two brothers started slacklining two years ago, his brother quickly excelled.

"Justin took off," Chris said. "I was slower to the learning curve, and I'm still learning from Justin and his tricks."

The summer after that Christmas, Justin practiced five or six hours each day once school let out for break. He did that again the next summer, and plans to slackline as much as possible this summer before heading off to the University of Puget Sound to study economics this fall, "with a minor in slacklining," he added, with a sly smile.

"I picked my college based on the trees," he joked. "Well, there have to be some trees."

Justin Wagers practices some slacklining routines at Bear Creek Park in Boulder on Thursday.
Justin Wagers practices some slacklining routines at Bear Creek Park in Boulder on Thursday. ( CLIFF GRASSMICK )

Gibbon Slacklines noticed Justin via his YouTube channel and short video clips he posted on Facebook. Now he's part of Gibbon's U.S. pro team, and his brother Chris is part of Gibbon's development team.

The brothers started slow, with a knee-level slackline, and learned how to walk without falling at first. Getting better and learning new tricks is what got Justin hooked, he said. Tricks can include front and back flips, spirals, jumps and "herkies," a half pike jump with one leg tucked flat behind the body. He compared it to both skateboarding and freestyle skiing in culture and style -- still a little bit underground.

Slackliners claim to get their roots from climbers in the 1970s and 1980s. The boys' dad Ken Wagers was an original slackliner, so to speak, while an undergraduate at the College of Idaho. He calls the line a "two-inch trampoline."

"We had an old tradition of putting climbing webbing between trees, but all we did was walk on it, we didn't do any tricks," he said.

Ken Wagers can still walk on the line, but doesn't do flips, spirals or chest bounces, he says. The boys' mom, Tina, will occasionally walk the line, too.

Justin's parents want him to get a degree. But Ken Wagers said he's been amazed at how far slacklining has taken his son. He's traveled the world as a professional athlete after hours and hours of hard work. Working with Gibbon as a sponsored athlete has given him a taste of the business world, too.

"He's grown up some and become more independent, and I think more confident in his abilities," Ken Wagers said, "Like 'I can do something challenging and difficult,' and I think that opens up his horizons about what he can do in his life."

Justin had shoulder surgery five months ago, but says he's back to 100 percent and ready to bring his best tricks to Vail. The competition is done March Madness bracket-style, with slackliners going head-to-head, two at a time.

Each slackliner has two minutes to show off his or her best trick, and the clock stops and restarts whenever each slackliner gets on or off the line. Three judges decide who advances, based on the difficulty of the tricks, amplitude and variety.

Justin wears a chest guard because he practiced too much one summer and damaged the cartilage in his chest. Slackliners bounce on their feet, chests and butts in between tricks.

"It looks really cool," Justin Wagers said of his chest guard. "People think it's like a sports bra."

The biggest misconceptions about the sport, he says, are that it's tightrope walking, or that slacklining is only for hippies.

In reality, it's more like finely crafted, daring choreography between two trees. It isn't easy, and Justin has his own "unique" style that fellow Gibbon slackliner Felix Carreira calls "that Justin style."

"I'm thinking about new tricks when I go to sleep, when I wake up," Justin Wagers said. "It's something to look forward to during the day and you can really be creative doing it."

--Follow Sarah Kuta on Twitter: @SarahKuta.