NEW YORK — "When the head comes to a sudden stop, if it's rotating, the brain material is twisting inside the head," Lloyd said. "That can cause concussion and brain injury, including life-threatening subdural hematomas."
The best helmet reduced the likelihood of concussion by 30 percent, Lloyd said. That may be because it was lighter than the other helmets, causing the head and neck to rotate less. It wasn't as good at providing protection against direct impacts that might shatter the skull, and didn't perform as well on standard tests, he said.
The study also found that football helmets fared better against linear impacts, which lead to bruising and skull fracture. Compared with dummies with no helmets, the football helmets reduced the risk of skull fracture by 60 to 70 percent and reduced the risk of brain bruising by 70 to 80 percent.
The research was released in advance of a presentation at the American Academy of Neurology's annual meeting starting April 26 in Philadelphia.
Lloyd suggested that taking the facemask off the helmet and switching to a soft helmet may help diffuse the impact, leading to fewer brain injuries. This is how the scalp works to protect the brain, moving to allow force to be spread and absorbed, he said. Helmets made of softer materials and without facemasks were used in football more than 50 years ago.
"If we got away from hard helmets, we could use advanced materials to provide protection for the head and brain," he said. "The only downside is you wouldn't have anything to attach a faceguard to."
Brains Inc., a company focused on the biomechanics of traumatic brain injury, supported the study.