University of Pennsylvania researchers, Douglas H Smith, MD, from the Department of Neurosurgery and the Head Injury Center at Penn School of Medicine, and David F Meaney, PhD, of Penn's Department of Bioengineering have concluded that medical science does not support the notion that rollercoasters produce forces large enough to harm the brains of riders.

Their findings are presented in the October issue of the Journal of Neurotrauma and contrast with the concerns raised by Robert J Brasiek MD and David J Roberts MD in their article for the Annals of Emergency Medicine in January this year.

'We should step back and separate the facts from the hype,' said Smith, co-author of the study. 'To our knowledge, no peer-reviewed studies have definitively linked brain injury in healthy individuals to riding the latest and most powerful rollercoasters.'

Meaney takes issue with the notion that the G forces experienced by riders are a potential danger. 'What we should be concerned about is not G forces, but the effects of rapid head acceleration - the rotational force on the brain that occurs as the body quickly changes direction,' he says. 'And when we predict head accelerations in rollercoasters - the sudden twists and turns - we find that they are well within established safety margins. It does not appear that rollercoasters produce high enough forces to mechanically deform and injure the brain.'

Using a simple mathematical model, the researchers examined the three basic features of G forces, as experienced by riders: the magnitude of the force, the direction of the acceleration and the time interval over which the acceleration occurs. They acquired G forces data from the Rock 'n' Roll Rollercoaster at the Disney-MGM Studios in Orlando; Speed - The Ride at the Nascar Café in Las Vegas; and Face-Off at Kings Island, Ohio. Using this data, they calculated peak head accelerations in three directions, assuming the head did not strike a surface.

Even considering the worst-case scenario, the researchers found that the largest forces experienced on rollercoasters were far below those known to cause injury. They proposed that the damage outlined in some published case reports trauma occurred as a result of pre-existing brain injuries. Even in those cases, researchers said that other factors - such as hypertension from the excitement of being on the ride - should be considered.