Helmets reduce the risk of serious head injuries by as much as 60 percent. So why do a surprising number of safety experts and ski and snowboard enthusiasts remain unconvinced that helmets reduce overall injury risk?img width='1' height='1' src='http://rss.nytimes.com/c/34625/f/640346/s/2809add1/mf.gif' border='0'/br/br/a href="http://da.feedsportal.com/r/151885005500/u/0/f/640346/c/34625/s/2809add1/a2.htm"img src="http://da.feedsportal.com/r/151885005500/u/0/f/640346/c/34625/s/2809add1/a2.img" border="0"//aimg width="1" height="1" src="http://pi.feedsportal.com/r/151885005500/u/0/f/640346/c/34625/s/2809add1/a2t.img" border="0"/