The researchers then wrote to the skiers and snowboarders to get more information on the injury and helmet use. "Wearing a helmet while skiing or snowboarding may reduce the risk of a head injury by 29 to 56 per cent," Prof Hagel says today in the British Medical Journal. "This may even be an underestimate if, as in cycling, the helmets were worn incorrectly, in poor condition or not designed for skiing or snowboarding."