Indoor trampoline park injuries are an "emerging public health concern," warn doctors in Injury Prevention - because over 6 months, 40 children needed medical treatment at just one trauma center following a visit to one of these venues.

Yes, they looked at results from one business and declare that parents have one more thing to worry about.

They reviewed the medical records of kids under the age of 17 who sought medical treatment at a children's emergency care department between July 2014 and January 2015 for an injury sustained while at an indoor trampoline park.

The closest trampoline park in the hospital catchment area is just under 6 km away; the venue opened in July 2014.

During the six month monitoring period, 40 children --55% of them girls--needed medical treatment for their injuries. Their average age was 10, but the youngest was just a year old.

Most of the injuries (33 cases) occurred while the child was on the trampoline and had been predominantly caused by a failed landing (18 cases). But in 8 cases the injury was the result of several people of different sizes using the trampoline at the same time.

In these situations, the higher energy from the larger bouncer is transferred to the smaller bouncer, prompting a mistimed landing or projection to an unexpected height or distance, say the study authors.

Over half the children (52.5%) were injured while involved in simple jumping activities. But five were attempting somersaults or flips at the time. And six children were injured when they landed awkwardly on something on the trampoline, which included the protective padding designed to prevent falls through the spring mechanisms.

Most of the children (55%) sustained bruising or sprains (ankles), but over a third fractured bones (elbows and ankles). And 5 (12.5%) required surgery and a hospital admission.

So the study sample is one park, and that children with more severe injuries might have gone to the hospital because it is a recognized trauma center, skewing the severity of injuries they treated, and that is a reason BMJ should be scaring people? Is it December yet, when they do their Christmas spoof issue?