Cammi Murakami recently celebrated her sweet 16 birthday with a few rounds of Knockerball. She slid herself into the inflatable sphere and let the straps fall on her shoulders like a backpack.

Knockerball is an activity in which both kids or adults don inflatable spheres that cover the top half of their body as they run and bounce off each other while playing soccer and other games. The spheres were introduced to the islands by Knockerball Hawaii in November 2014 and the sport has been gaining in popularity as more people are exposed to it.

Fourteen teens joined Murakami to celebrate. They used the spheres to play soccer and party games at Kapiolani Park while in the 1.5-meter-diameter balls.

“It’s fun to run into people and knock them down. I really didn’t have enough force to knock people over,” Murakami said. “It’s physically demanding and we were out of breath. But there’s enough cushion so we didn’t get hurt. It was lots of fun.”

Quinn Sanford, owner of Knockerball Hawaii, rents out the equipment, including goals and field markers, for events.

“If someone has 20 guests at a party, we suggest that they get 10 balls. People get tired and they take turns,” Sanford said.

Novices are held in place by harnesses and can control their movements by holding onto the handles inside the 14- to 17-pound balls. There’s quite a bit of cushion at the top so even if you end up upside down, it’s still OK, Sanford said.

“Getting up is the hardest part, and you fall down a lot,” Sanford said.

Renting two balls for two hours costs $199; for 10 balls for two hours, $379. Smaller, 1.2-meter-diameter balls are available for 8- to 12-year-olds and recommended for anyone under 5 feet tall.

In addition to party rentals, Sanford hosts open play, during which curious people can try out the fun. At open play, Knockerball Hawaii charges participants $15 for a 75-minute session. Participants are required to wear athletic shoes; knee pads are optional but recommended.

Visit knockerballhi.com/open-play.html for times and dates of open play sessions. Call Knockerball Hawaii at 388-0587 for more information on open play or rentals.