Akory Coates lived out his basketball dreams for an hour recently at a Sky Zone trampoline park in Torrance, Calif. He jumped; he twirled in the air; his fingertips grazed the rim; and he made four baskets. Not an easy feat for a 9-year-old, but a series of trampolines beneath his feet gave him all the lift he needed.

“Hey, Dad, look at me,” Akory said as he went up for a basket and made it. His father took the fourth-grader and friends to the park for the boy’s birthday. Across the warehouse a SkyRobics exercise class was under way, and a small group of parents watched kids tumble.

The indoor trampoline business is booming, with dozens of parks open or in the works across America.

“Since early to mid-2010, the whole industry has exploded,” said Jeff Platt, chief executive of Sky Zone Indoor Trampoline Park, a Los Angeles company that opened its first location in Las Vegas in 2004. “People started feeling a little bit better about the economy and were looking for something new to do.”

Experts say trampoline parks appeal to people of all ages eager for a relatively inexpensive activity and exercise. An hour at these parks typically ranges from $10 to $15. Many of them offer birthday parties, aerobics classes, corporate events and dodge ball games. There are also foam pits for people to jump into, and there are pizzas and hot dogs at the snack bar.

“We’ve seen them take off,” said Dennis Speigel, president of International Theme Park Services Inc., an industry consultant. “They’re not taking off like the space shuttle, but we are seeing a reemergence of them.”

Speigel said trampoline parks came into existence in the late ’50s and early ’60s but fell out of favor because of liability. Today’s trampoline parks, he said, are attractive to teens and preteens who like extreme sports such as skateboarding, BMX and snowboarding.

Sky Zone has opened 27 parks — three company-owned and 24 franchises. At least four other companies have opened trampoline parks across the country. Sky High Sports has 15 outlets. Jump Street has nine locations combined in Arizona, Colorado and Texas, with plans to open two more. Xtreme Trampolines has two locations in the Chicago suburbs. Rebounderz has one outlet in Florida.

Jerry Raymond, CEO of Sky High Sports and a founding member of the International Association of Trampoline Parks, estimates that there are more than 100 facilities in the United States.

Platt, Sky Zone’s CEO, said the key to a successful trampoline franchise is new activities.

After Sky Zone’s revenue started to decline in 2009, five years after opening, it introduced dodgeball, then workout classes and basketball. The moves paid off. Last year Sky Zone posted about $16 million in revenue, and it’s projecting $70 million for 2013.