DOHA - United States swimmer David Johnston swam a personal best to top qualifying for the 400 metres medley final at the World Championships on Sunday, while Canada's Tessa Cieplucha took top seed for the women's 400m.

With France's world champion Leon Marchand skipping Doha, Texas University student Johnston won his heat in four minutes and 12.51 seconds to upstage U.S. team mate and defending silver medallist Carson Foster, who qualified fourth.