News On an incredible night in Rio de Janeiro's Olympic Aquatics Stadium, Katie Ledecky gave the USA its first swimming gold medal of the Rio 2016 Games with a world record in the women's 400m freestyle And it was another day, another personal best for Great Britain's Adam Peaty, who broke his own world record in the final of the 100m breaststroke Not to be outdone, Michael Phelps, the world's most decorated Olympian, helped the USA to the 4x100m freestyle relay gold, taking his personal tally to 19, and his overall total to 23 And Sweden's Sarah Sjostrom clocked 55 48 in the 100m breaststroke to win gold in the world-record time At his fifth Games, Phelps admitted the atmosphere in Rio was something special  "It was crazy," he said "I was standing on the blocks while Caeleb (Dressel) was coming in and I honestly thought my heart was going to explode out of my chest "Having that amount of excitement, cheering in the stands during that race, I don't know if I have heard anything like it " The Ledecky result was totally expected The 19-year-old has dominated the longer freestyle events since winning gold in the 800m at London 2012 as a 15 year-old  The American kicked off the first wall with a lead of nearly a body length and steadily pulled away as her powerful arms churned through the water   When Ledecky saw the time — three minutes, 56 46 seconds — she let out an uncharacteristic scream and pumped her right fist She had crushed the mark of 3:58 37 that she set nearly two years ago on the Gold Coast of Australia, and had been chasing ever since "It's pure happiness," she said afterwards As it happened: relive the drama of Sunday night in the pool Peaty, 21, took gold in the men's 100m breaststroke on Sunday night with a time of 57 13 seconds, shattering the mark of 57 55 he set one day earlier in the preliminaries  Peaty cruisied away from defending Olympic champion Cameron van der Burgh of South Africa, who took silver in a time of 58 69   Peaty's 74-year-old grandmother Mavis, who has become an internet sensation with her enthusiastic tweets supporting her grandson, was quick to take to the twittersphere again The bronze went to Cody Miller of the United States, whose time of 58 87 held off team-mate Kevin Cordes  The crowd at the Olympic Aquatics Stadium went into frenzy at the sight of two Brazilians in the final But Joao Gomes finished fifth and Felipe Franca was seventh On a night of records, Sjostrom clocked 55 48 in the 100m breaststroke to win gold  Almost a second behind was Canadian Penny Oleksiak, who took silver in 56 46 followed by Dana Vollmer of the USA who won bronze in 56 63 In total, there have been seven world records set at the Rio 2016 Games so far (including Peaty breaking his own mark twice), with five of them coming in swimming   In the last final of the night, Phelps and USA captured gold in the men's 4x10om freestyle relay France claimed the silver and Australia took the bronze