A growing sport described as “pure difficulty” where competitors earn comparisons to Spider-Man is bringing its national championships back to Madison for a second year.

The Bouldering National Championships take place Friday and Saturday at Monona Terrace, with youth and other competitions set for the following weekend.

“You don’t understand how breathtaking and athletic of a sport it is and how much high drama there is unless you see it in person,” said Jamie Patrick, vice president of the Madison Area Sports Commission, which is responsible for bringing the event to Madison.

Bouldering is like rock climbing except that it’s done without equipment, said Brad Werntz, founder of Boulders Climbing Gym on Madison’s North Side. There are no ropes, no harnesses. There’s also no belayer, which is used to catch a climber’s fall, provide tension on the rope through difficult sections, and lower a climber back to the ground.

There’s just a big pad to catch climbers.

“You climb as hard as you can and as high as you can, and when you get to the top, you drop off into this kind of bouncy-castle-type of pad,” said Werntz, who describes the sport as “pure difficulty.”

USA Climbing, which sponsors the American Bouldering Series national championships, builds the climbing walls at Monona Terrace over eight days, and sets new “routes” for climbers between each round of competition.

“I was able to watch them last year. It’s part poetry and part science of the route builders building it,” Patrick said. “It’s a very artistic and thoughtful process.”

Adding to the interest is the fact that climbers don’t see the course before they tackle it, said Judy Frankel of the Greater Madison Convention & Visitors Bureau.

“It’s a lot of Johnny-on-the-Spot thinking about how they are going to maneuver effectively and efficiently on a course that they are not familiar with,” she said.

Climbers are ranked according to how high they climb on each of the boulder routes in a round and how many attempts it takes them to reach that high point, said Angie Payne, a spokeswoman for USA Climbing.

The sport is called bouldering because the athletes climb on relatively short rocks (boulders) or relatively short man-made walls without ropes.

Kynan Waggoner, CEO of USA Climbing, said people initially wondered why the organization had picked Madison for its championship, since it’s not exactly a climbing mecca. And January and February aren’t particularly friendly times to be in Wisconsin.

“That belief happened until they walked into the doors of Monona Terrace. Once they saw the quality of the venue — the venue itself was elevating the perceived professionalism of our event,” said Waggoner, who is based in Boulder, Colorado.

With the help of management at Monona Terrace, the group was able to put on the best national championships yet in 2014, he said. “That became quickly evident with the attendees last year.”

It was standing room only for the finals with about 1,600 people at Monona Terrace, Patrick said.

Not only is climbing growing globally, it’s growing locally. Boulders, which opened in 1996, has been getting more popular in recent years, with Werntz pursuing potential second and third locations in Downtown Madison and in the Fitchburg-Verona area. Each gym would have a different format, he said.

The current location at 3964 Commercial Ave. started at 8,000 square feet and added about 3,000 square feet a couple of years ago. It has about 14,000 square feet of wall space for climbing.

As for the championships at Monona Terrace, GMCVB’s Frankel said bouldering is a spectator-friendly sport because while there are rules, it’s easy to figure out what the objective is for the athletes.

“It has what’s been described as a very X Games kind of atmosphere. It’s got the pulsing music and the lights. It has a lot of built-in theatrics,” she said.

Some of the athletes appear to be hanging vertically like Spider-Man, Frankel said, adding, “I don’t even know how they do it.”

Then there’s the youthful, energetic atmosphere of the event, which Frankel said is uplifting at this time of year.

“Couldn’t we all just use a little injection of excitement?” she asked.