Olympic superstar Michael Phelps won the 100m freestyle at the Pro Swim meeting in Austin, Texas, sharing the opening day spotlight with Sarah Sjostrom and Katie Ledecky.Phelps, out of retirement and aiming to add to his record tally of 18 Olympic gold medals at the Rio Games in August, powered home on Friday to win the 100m butterfly in 51.94sec, with fellow American Tom Shields second in 52.39 and Tim Phillips third in 52.61."I`m happy to be able to do that double and go 51.9," said Phelps, who also swam 49.77 in the men`s 100m free, good for sixth in a race won by America`s 2012 Olympic gold medalist Nathan Adrian in 48.91.France`s Jeremy Stravius was second in 48.96, with American Jimmy Feigen third in 49.20.Sweden`s Sjostrom produced a gold medal double, winning the 100m butterfly and 100m free in US Open records.Sjostrom, who twice lowered the 100m fly world record in winning the world title at Kazan, Russia, last year, edged 2012 Olympic gold medalist Dana Vollmer of the United States with a time of 56.38 to Vollmer`s 57.61.Sjostrom won the 100m free in 53.12 with Ledecky, better known for her dominance in distance freestyle, second in a personal best of 53.75.Abbey Weitzeil was third in 54.00, while Hungary`s Katinka Hosszu finished off the podium in fourth in 54.37.Ledecky`s 100m free time would have won at the 2012 US Olympic trials and made her the second-ranked American in the event last year behind Missy Franklin.No US woman has ever raced the 100m, 200m, 400m and 800m freestyles at one Olympics.Even if Ledecky doesn`t pursue the 100m free in Rio, the 18-year-old is clearly staking a claim to a spot on the 4x100m free relay team.But the 100m free was just a warm-up for Ledecky, who returned to win the 400m free in a scintillating 3min 59.54sec-fifth-fastest ever in the event.Ledecky owns four of the five fastest 400m free times ever, including her world record of 3:58.37 set in 2014."I think going under four minutes was really good coming off the hundred, and I can still take away a lot of things coming off those two races," Ledecky said.