A new trend on the social media app TikTok is causing severe injuries to teenagers and has doctors concerned about its potentially deadly consequences.
The "skull-breaker challenge" involves two people tricking a third person into jumping into the air and then kicking their feet out from under them.
US student Kathleen DeJesus, 13, was a target in the challenge and had to stay in hospital for two days with a severe concussion.
She told ABC News she was screaming for an ambulance after the incident happened at her Massachusetts school.
"I was thinking 'oh my God I'm going to lose my life over this game'. I should have never done it."
Another school student who was a victim in the trend, Olivia Ross, says older students asked her if she'd jump in their TikTok video.
"I remember blacking out for a second and I started to get an instant pressure headache," the 14-year-old from Portland, Oregon says.
But the potential long-lasting injuries are concerning doctors, who say the consequences of the trend could be deadly.
"The injuries can stem from a severe concussion, a skull fracture, a neck fracture... which could result in paralysis," Dr Richard Lebow of Medstar Union Memorial Hospital told WJZ Baltimore.
"Plenty of wrist fractures from trying to break your fall. Literally, if you bleed inside your brain, it could result in death."
This isn't the first time a TikTok challenge has had doctors warning about its potential fatal consequences.
The "pass out challenge" had users rolling their heads back and forward repeatedly to make themselves faint.
Thousands of people took part in the trend and many reported getting severe headaches.