Getting bumped to the ground usually doesn't send adults into belly-aching bursts of laughter.
However, if they don giant inflatable suits before colliding with each other, it's a different story.
Those big hits make knockerball so addicting, according to one pair of enthusiasts, who are trying to bring the new and unusual sport to the masses in the Quad-Cities.
Since quitting their restaurant jobs about two weeks ago, Aaron Filgo and his girlfriend, Miranda Sneade, have been bouncing around parks in their respective bubbles to draw curious passersby.
"I want everybody to experience this, especially people who have high-stress jobs," said Filgo, a heavily tattooed and bearded 29-year-old, who lives in Davenport. "I just want to get that laugh out of them."
Fully inflated, the forgiving plastic spheres, which come in two sizes — 1.2 meters (22 pounds) and 1.5 meters (28 pounds) — cover the entire upper half of most players.
That protection allows participants to jump into each other and roll on the ground without injuring themselves, said Filgo, who spent a lot of time researching the product's safety and track record before making an investment.
"You do take some hits, but nothing worse than what you're going to do playing a regular game of soccer," he said, adding that ankle and knee injuries happen but head injuries are more rare. "We haven't had anybody get in one and say, 'Ouch, it hurt too much,' or 'I'll never do it again.'"
Prior to using their equipment, first-timers must sign a waiver. In return, Filgo and Sneade teach newbies basic safety and mobility tips.
Under the name Quad-City Knockerball, the couple hopes to recruit enough players in the coming weeks to form a knockerball soccer league.
Additionally, Filgo said the suits can transform any children's game, such as Red Rover and capture the flag, into a full-contact sport.
They currently own 10 knockerballs, which they purchased from Knockerball USA. The organization has helped more than 400 startups launch knockerball businesses throughout the country, the company's website reports.
"It's huge out West, big in the Southeast, and it's slowly moving toward the Midwest," Filgo said.
Quad-City Knockerball rents out eight balls at a time, which costs $200 for the first hour and $100 per hour after that.
After every outing, Filgo said they clean their gear with disinfectant wipes.
Sneade, 23, called the activity an "undercover" workout, one that sneaks up on her every time she exercises in one of the suits.
"You're just out there having fun, and you don't even really notice it," she said, before suiting up for a round of somersaults. "It's like running around in a hamster wheel."
The entrepreneurs unloaded their knockerballs on Thursday at Crow Creek Park in Bettendorf, where they introduced the sport to a few of their friends.
Following his first trial run, Sean McQueen, 45, who works at Mississippi River Distilling Co. in LeClaire, couldn't get enough of the action.
"It's so much fun," he said, "but kind of humbling.
"I thought I was in a lot better shape than this."
Filgo, a Pleasant Valley High School grad who worked a factory job before starting his previous restaurant gig, said he kicked the knockerball idea around for about a year before pulling the trigger.
Together, the couple has invested about $7,000 in the venture, and they plan to spend another $15,000 this summer to secure an indoor site for the winter.
"I've never been the super active type, but when I saw it online, I knew it was something that I wanted to be a part of," Filgo said. "I just didn't know I would own 10 of them, and potentially 30 or 50 of them soon."