One man's experience led doctors to warn of roller coaster risks
The twists and turns of a roller coaster ride can leave you breathless - but US doctors warn it could also cause temporary hearing loss.
The Detroit team report a case where a man turned to speak to his girlfriend on a ride - exposing his ear to the full impact of acceleration.
It led to an ear injury more commonly linked to scuba-diving or air travel.
A UK expert said the problem could be seen more often as roller coasters became higher and faster.
The injury the 24-year-old experienced is a barotrauma, which occurs when there is a relatively quick change in pressure between the external environment, the ear drum and the pressure in the middle ear space.
Symptoms include dizziness, pain and a sensation of having the ears "pop". In the most severe cases, it can lead to temporary hearing loss.
He had turned his head to the left to speak to his girlfriend as the ride began to accelerate.
The ride he was on reached a top speed of 120 mph within four seconds.
Two days later, he started to experience pain in his right ear.
When doctors examined him, they found his left ear was normal, but the right ear canal was swollen and the ear drum was inflamed.
It was estimated his right ear had been exposed to around 0.6 PSI (pound per square inch, used to measure pressure) when the roller coaster accelerated.
The team from the Henry Ford Hospital said that, since the injury from a roller coaster happens suddenly, it is very difficult for the patient to equalise ear pressure by the usual measures of yawning or chewing gum.
Dr Kathleen Yaremchuk, head of the department of otolaryngology at the hospital, said: "As roller coasters continue to push the envelope of speed, otolaryngologists need to be aware of this new cause of barotrauma to the ear.
"Based on our research, we recommend that passengers remain facing forward for the duration of the ride to not let the full impact of acceleration hit the ear."
The patient's symptoms improved within a few days.
But the Detroit team, which presented its findings to the US Triological Society's annual meeting in Las Vegas, said roller coaster fans should not be put off.
Dr Yaremchuk said: "This was an unusual situation, where the rider turned his head at just the right time to experience the full force of acceleration against his ear drum.
"It would be highly unlikely to do this multiple times in a row, but roller coaster riders should be aware of what they can do to prevent barotrauma from occurring."
Alan Johnson, president of ENT UK, said: "Generally with roller coasters you are just a few hundred feet up in the air, so the variation in pressure isn't that great.
"But it might become an issue if you have huge drops or changes of speed, particularly if a person has a cold."