American ski superstar Lindsey Vonn pulled out of Sunday\'s World Cup slalom race here with a sore back, the American Ski Federation announced. Vonn, triple World Cup overall winner from 2008-10, explained after her disappointing first leg in the giant slalom on Saturday when she recorded the 21st fastest time that she had felt pain in her back over a week ago. Vonn, who eventually finished 12th in the giant slalom, had to stop training for four days prior to the World Cup races here. Vonn, who started the season in style by winning her first career giant slalom in Solden, Austria, will focus on being fit for next weekend in Lake Louise, Canada, where there are two downhills and a super-G. It is a course where she has enjoyed a lot of success winning eight times and finishing on the podium on six other occasions.