Improved helmet design has helped reduce concussions in impact sports, but it may be impossible for a helmet to completely prevent them. A panel of sports science professors outlined their latest findings on Monday. Helmets "certainly help to mitigate forces that are distributed by impact to the skull and the intracranial cavity and the brain," said Kevin Guskiewicz, a professor of sports science at North Carolina and an expert on football helmets. "But the brain is still going to move inside that cranial cavity regardless of whether there's a helmet on or not." With improved soft materials inside its hard outer shell, a modern helmet can lessen the effect of a straight-ahead, "linear" impact, but can't do much to prevent the effects of the head rotating from the impact. Improvements in design have made a tremendous difference in preventing disastrous head injuries such as brain bleeds, hematomas and skull fractures. "These helmets are doing very well at preventing really catastrophic crashes," said Jason Mihalik, an assistant professor of sports science at North Carolina.