Ziplines are becoming more and more popular and as they do, injuries are soaring, a new study finds.
Researchers found the injury rate from ziplines rose by more than 50 percent between 2009 and 2012, with kids 9 and under accounting for 45 percent of the injuries.
"One of the things that really struck us about this study is how serious the injuries were. Almost 50 percent of them were fractures or broken bones, and over 10 percent actually had to be admitted to the hospital," said Tracy Mehan of Nationwide Children's Hospital in Columbus, Ohio, who led the study.
"These are much higher and more serious injuries than we see with a lot of studies, and it shows us that this activity is much more like an adventure sport," Mehan told NBC News.
Her team looked at a national database of emergency room visits. They found 16,850 people have been injured badly enough on a zipline to visit an ER since 1997.
There were not enough annual cases until 2009 — when ziplines really began to be popular — to put a good, solid rate on the number of injuries.
"Seventy percent of them were in the last four years, which shows us that this is a growing trend," Mehan said. "In fact, in 2012 alone, there were over 3,600 injuries, which was about 10 a day."
It's clear why: Ziplines have taken off in popularity.
"In 2001 there were about 10 commercial zipline outfits in the United States," Mehan said. "By 2012 this had grown to over 200. And when you add in all of the publicly accessible ziplines that you see now, it's over 13,000."
Most of the injuries happened when people fell off or crashed into something like a tree or a zipline structure.
"The injuries really happen when you fell off the zipline from a high height, or when you went careening into a tree at a high speed or a support structure and had a collision. Those types of injuries are very serious," she said.
"The most common injury by far that we see are broken bones. That was almost 50 percent of our injuries. Other injuries can be bruises, sprains and strains, or concussions."
Saul Bronstone of Walnut Creek, California, is one of those victims. He was 10 in 2012 when he fell off his family's back yard zipline and hit his head.
"When I fell and hit the ground, my head hit a rock," Saul, who is now 13, told NBC News.
Saul's father, Trace Bronstone, said it didn't seem too serious at first. "He was complaining about his head, so our parental instincts kind of took charge at that point," he said. They took him to the hospital.
"We thought we'd be there for just a couple of hours and they would tell us just a bad bump, not to worry," Bronstone said. "But after several hours, they told us that he was not going anywhere."
A CT scan showed a cracked skull and some bleeding in the brain.
"The worst feeling in the world is to see your kids in intensive care with tubes coming out of them and people taking scans," Bronstone said.
Head injuries like Saul's account for 7 percent of hospital visits, Mehan's team reports in the American Journal of Emergency Medicine.
Saul wasn't wearing a helmet, but a helmet doesn't guarantee anything. Even a fall from a short height can damage the head and neck, even with a helmet.
Bronstone say his family's zipline wasn't too long and wasn't too high.
"I want to say 150 to 200 feet in length — maybe …not very high off the ground, and we had subsequently learned it doesn't have to be very high off the ground to have .. for your kids to have problems if they fall," he said.
"It's not necessarily how far they fall but how they fall and what they fall on that can be a problem."
The dual zipline — they had a fast line and a slow line — is disconnected now. "We have three boys and they're very active and so they thought that a zipline would be a very good activity to keep them occupied," Bronstone said.
Mehan said safety standards might help.
"I think a lot of families assume that if there is a zipline out there, that it is following industry safety standards and it's being kept up and maintained in a way that is safe, but that's not always the case," she said.
"Not a lot of states actually have standards in place. Some do, some don't, and even among those that do, it can even vary among jurisdiction," she added.
"We would like to see one universal set of safety standards adopted by each state."
Saul's recovered, but the accident cost him many months of recovery.
"After that, for a long time, I couldn't really walk," Saul said. "My mom and dad had to help me. I couldn't read the whole summer. I couldn't do any sports. I just sat the whole day doing, like, nothing, like physical therapy and that type of stuff."