Swimming: Missy Franklin sets personal best in 100m freestyle heat at world c'ships

BARCELONA (REUTERS) - Missy Franklin surprised herself by going second-quickest behind Australia's Cate Campbell with a personal best in the heats for the women's 100 metres freestyle on Thursday as the American teenager chases a fourth world championship gold of the week.

With titles in 200m freestyle, 100m backstroke and 4x100m freestyle relay already in the bag at the hilltop Palau Sant Jordi, the bubbly 18-year-old touched in a time of 53.36 seconds, just behind Campbell in the next lane in 53.24.

Franklin, who won four Olympic golds and a bronze last year, is aiming to make up for the disappointment of finishing fifth in the event in London in a race won by Ranomi Kromowidjojo of the Netherlands, fifth fastest in Thursday's qualifying.

"I am so happy with that time, a little bit surprised by it actually, I didn't think I was going to go that fast this morning," Franklin told reporters ahead of the semi-finals later on Thursday and Friday's final.

"I felt really great and it's always really great racing Cate Campbell," she added.

"If I can make the podium I'll be over the moon happy."