The secret to walking on a slackline is simple: Stand up, fall down, stand up, fall down, stand up, fall down.

Rinse, repeat.

“You just stand up more times than you fall down, and that makes you a slackliner,” says Johnson City slacklining instructor Kimberly Margaret. “You just have to keep at it.”

Slacklining, which involves balancing on a 1- or 2-inch strip of webbing stretched between two anchor points, has been growing in popularity since a pro performed tricks on a slackline during Madonna's half-time show at the 2012 Super Bowl.

Slacklines, typically made with woven nylon and polyester, are similar to tightropes, except they're not as taut — hence the name. That means they move and flex and bounce beneath the feet — hence the likelihood of falling off when first trying it.

“I was really proud when I went five steps,” says Michaela O'Brien, 38, who runs the San Antonio Slacklines group on Facebook.

But walking on a slackline is just the beginning. While some slackers, as they call themselves, like to see how far they can walk on a line, others prefer the thrill of walking on a line strung over water (waterlining). Some do stunts (tricklining). Some do yoga poses (no, not yogalining, yoga slacking).

“When you do your regular yoga pose, it's like, 'How do I have to hold this?' When you do it on a slackline, it's like, 'How long can I hold this pose?'” says Mark Stewart, 20, who teaches slacklining at the District, a rock climbing gym and fitness studio on Broadway.

Then there's highlining, balancing on a line strung far above the ground. Gibbon Slacklines, which manufactures lines, rigged a high line over the San Antonio River by the downtown Convention Center in March for a demonstration.

Naturally, that event drew a lot of attention from passersby, but O'Brien says even when she sets up a line just a few feet above the ground in Brackenridge or McAllister parks, strangers often wander up and want to jump on.

The District is adding a slacklining room, expected to be completed in the summer, to keep up with the growing demand from clients interested in trying it out.

Gibbon Slacklines is promoting slacklining as a sport for advanced slackers. They have a pro team that travels the country, and Gibbon also holds competitions in tricklining, in which competitors are judged on stunt difficulty, creativity and performance.

“They do what a gymnast on a balance beam does on a line that's moving,” says Emilio Torres, a Gibbon spokesman. “It's a sport that's intriguing and fun to watch, like X Games. It's a head-to-head battle. Each gets two minutes on the line. The winner moves on, the loser goes home.”

Stewart calls tricklining “really scary, but really awesome” and “an adventure, a painful one.” Most tricks involve leaping, spinning, bouncing or a combination of leaping, spinning and bouncing.

But with enough practice, anyone can succeed at basic slacking, says Margaret, 39, a certified YogaSlacker instructor, who originally bought a slackline for her teenagers but ended up mastering it herself.

“I've seen people of all different sizes get up and slackline,” she says. “I've seen huge, huge men just plow across the line. And little kids. I think you have to have a healthy measure of tenacity. Generally, it's not super easy at first. You're retraining your body. You use muscles you don't usually use, teeny tiny stabilizer muscles.”

Slacklines are available beginning for about $70 online. Beginners can string them up just a few feet above the ground, so it's easy to step off if you lose your balance.

Slackers say it's a great physical workout, especially for the core, but don't discount the mental component.

“It's intensely focusing,” O'Brien says.