The American Gym offers some tips on safe pit construction:
… Training pits should be longer and wider than competition matting requirements. Since gymnasts have not yet mastered the skills they will be performing, like they would in competitions, they need a larger margin of safety …
Gymnasts competing skills on to hard mats that they’ve obviously rarely done on to competition mats.
Coaches should do a better job of simulating the competition landing in training.
The best I’ve ever seen was T&T coach Tammy Stephenson. She trained landings on to very high, very soft surfaces for most of the year. Prior to a competition she alternated layers of matting stiffened with sheets of plywood.
Gymnastics foam pits were first. Ball pits soon after.
The invention of the ball pit (or “ball crawl,” as it was first dubbed) is widely attributed to Eric McMillan.
… In 1971, he was appointed chief designer of Ontario Place, an ambitious project that included a park, theme park, and the world’s first IMAX theater on newly built artificial islands just off the Toronto waterfront. Ontario Place was a visionary project, but it was missing something.
Striving for a more kid-friendly environment, the designer created The Children’s Village, a massive playground unlike any other, where youngsters could climb huge rope nets and soft pyramids, crawl through hanging tunnels, and jump on an enormous air mattress. “The Children’s Village opened in July 1972 …
McMillan did not install a ball pit in Toronto, however.
According to McMillan, that honor belongs to the ball crawl he installed in 1976 at SeaWorld Captain Kids World in San Diego, another of a handful of theme parks McMillan designed …
Yesterday, @BoiseFire came out to practice a foam pit rescue! A unique but important skill to have in the world of college gymnastics. Thank you for coming out, you guys were amazing! (That foam pit can be hard to get out of) #BleedBluepic.twitter.com/ZIpQWXp82K