Swimming: Lauren Boyle misses out on final

Lauren Boyle.

Olympic medal hope Lauren Boyle has missed out on the 400m freestyle final at the Rio Olympics after finishing fifth in her heat.

Boyle, 28, clocked four minutes, 07.90 seconds in the last of four heats, won in an Olympic record of 3:58.71 by American teenage phenomenom and world record holder Katie Ledecky.

The Commonwealth Games 400m freestyle champion, Boyle has batted illness and a throat infection in her build-up to Rio and struggled throughout to stay in touch with the leaders. She was only 14th fastest and more than three seconds off the time needed to make the final.

Boyle, who finished fourth over 400m at the London Olympics, is also targeting the 800m at Rio, hoping to emulate the silver medal she won at last year's world championships. Earlier, teammate Corey Main set a new personal best to book a semi-final place in the 100m backstroke.

The Florida-based 21-year-old dipped under the 54 seconds for the first time to win his heat.

His time of 53.99 ensured he was the last of 16 qualifiers for the semi-finals on Sunday night at the Olympic Aquatics Stadium. It shattered his previous best of 54.27 but was still almost two-thirds of a second shy of Gareth Kean's national record.

France's Camille Lacourt was fastest qualifier with 52.96.

Freestyler Matthew Stanley missed out on the semi-finals of the 200m after finishing second in his heat with 1:47.37, fractionally outside his New Zealand record of 1:47.09 set two years ago.

That was the 20th fastest time but not fast enough to advance.

Stanley, 24, has been battling an ankle injury, and earlier this week pulled out of the 400m believing he didn't have the conditioning to contest the longer event.