DOHA - Defending champion Sarah Sjostrom was fastest in the women's 50 metres freestyle preliminaries at the World Championships in Doha on Saturday ahead of her bid for a sixth successive 50m butterfly world title.

The evergreen Swede comfortably won her heat in 23.91 seconds at the Aspire Dome pool, nearly three-tenths of a second quicker than the United States' second-ranked Kate Douglass (24.19).