After eight days of intense competition, surprise results from newcomers and stand-out performances from veteran swimming legends, the USA Olympic trials ended in Omaha on Sunday (3 July) with the presentation of the official team for Rio 2016 to a 14,000-strong crowd.

The 'Big Four' of Michael Phelps, Ryan Lochte, Missy Franklin and Katie Ledecky have all taken their places in the 47-strong team, joined by a host of new faces who have burst onto the international swimming scene over the course of the week.

Phelps, the world's most decorated Olympian, will be trying to add to his haul of 22 medals when he competes at his last Olympic Games in Rio. He has qualified for the 100m butterfly, 200m butterfly and 200m individual medley and will also be a candidate for the relays. Joining him in the 200m medley will be his long-term rival and friend Ryan Lochte. The 11-time Olympic medallist will also be racing in the 4x200m freestyle relay.

In the women's events, Katie Ledecky was the stand-out performer of the week in Omaha and will be competing at Rio 2016 in the 200m freestyle, 400m freestyle, 800m freestyle and the 4x200m freestyle relay. Five-time Olympic medallist Missy Franklin, who endured a tougher trials, did not win an event but will join Ledecky in the 200m freestyle and the relay and will also race in the 200m backstroke.

Michael Phelps and Katie Ledecky are two of the established stars who will be competing in Rio (Photo: Getty Images/Tom Pennington)

In the backstroke event, Franklin may be the reigning Olympic champion and world record holder but she could finish only second in Omaha. First place in the race went to Maya DiRado, one of the charismatic new stars of American swimming . The 23-year-old Stanford student will also represent the USA in the 400m and 200m individual medleys. DiRado, Ledecky and Phelps were the only three-time winners in Omaha. 

DiRado is one of a total of 30 rookies on the USA's Olympic swimming team. Joining her will be her Stanford team-mate and training partner Simone Manuel, who will be racing in the 50m and 100m freestyle and the 4x100m freestyle relay. Manuel was in tears of joy to be coming to Rio.

In the men's events, rookies Jay Litherland and Chase Kalisz in the 400m individual medley, Caeleb Dressel in the 100m freestyle and Ryan Murphy in the 100m and 200m backstroke all look like medal contenders.

The USA won 31 medals at London 2012, 16 of them gold, and is the dominant force in world swimming. Ominously for rivals, men's team coach Bob Bowman said he expected the country's new swimming stars and established talents to post faster times at Rio than at Omaha.

"Going forward we are going to have to step up to a new level and we will see some new faces step up at the top," Bowman said. "One of the things we have always done well, better than anyone else, is improve from the trials to the Games.

"We have our tried-and-true guys and I think with Michael and Ryan we're going to be able to count on them, but it's going to be very exciting to have a new group of guys step up ... and kind of take us into the next era of swimming."