Experts warn of 'catastrophic injuries' as trampoline parks jump in popularity

Over the past several years, trampoline parks have grown int a billion-dollar industry. But with that growth comes a downside.

confirms in the last seven years, at least six people have died from injuries at trampoline parks.

"That number could be even higher because many of those injured are often forced into arbitration and sign confidentiality agreements that stop them from speaking out," CBS News' Meg Oliver reports.

In one video from a trampoline park in New Jersey shown to CBS News by an attorney representing more than a dozen people injured at trampoline parks, you can see a father unknowingly causing what's known as a "double bounce."

The man's 4-year-old son falls to the mat, and "the force of the trampoline coming back up after the father's hop across broke the 4-year-old's femur," the attorney says.

The video shows it took almost a full minute before anyone realized the child was injured.

CBS News reports that state lawmakers in Utah recently passed a new law to try to make trampoline parks safer, joining "at least seven other states requiring more oversight from insurance companies and annual inspections,"

One expert who's coached gymnastics for more than 40 years says the danger with the parks lies in the design as several trampolines are connected with steel cables or chain links under the padding.

"As people jump, waves of energy are generated in all directions, which can cause those "double bounces" that can end in high-impact collisions," CBS News reports.

The impact can be enough to cause severe injuries, or even deaths, longtime gymnastics coach Don McPherson says.

"They're moving at speeds and with energy that when they hit or get hit by somebody else that's twice their weight, they end up with crush injuries," he says.

Over the past few years, CBS News reports emergency room visits from trampoline park injuries have skyrocketed.

"According to the Consumer Product Safety Commission, the numbers have shot up from 2,500 in 2013 to almost 18,000 in 2017," CBS News reports.

In response to deaths and injuries, the International Association of Trampoline Parks issued the following statement to CBS News: