News A Japanese duel to find the winner of what Michael Phelps called “swimming’s decathlon”, the 400 metres individual medley, will illuminate the first day of action at the Olympic Aquatics Stadium this Saturday (6 August) The first gold medal to be won in the week-long Rio 2016 Olympic Games swimming programme looks likely to go to one of two great friends, world champion Daiyo Seto or the world’s fastest man this year, Kosuke Hagino, in the four-stroke event Chase Kalisz and Jay Litherland, who prevented Ryan Lochte from having the chance to defend his title by finishing one-two at the US trials, could be the pair to split the Japanese In the equivalent women’s event, Katinka Hosszu, holder of 11 long and short-course world titles, is the clear favourite in her fourth Games to finally land her first Olympic title as, on 2016 form, the Hungarian is over three-and-a-half seconds faster than world No 2 Hannah Miley, of Great Britain The men's 400m freestyle has enjoyed a feisty warm-up with the two favourites, champion Sun Yang of China and Australia's Mack Horton having, according to reports, been involved in a spat at the Rio warm-up pool Follow the Rio 2016 swimming competition here World champion Sun is pursuing a unique 200m, 400m and 1500m freestyle treble but his hopes are threatened on this first leg, not just by Horton, who has swum 1 9 seconds faster than him this season, but also by the likes of Connor Jaeger, the USA trials winner, Britain's James Guy, the world 200m champion, and Park Taehwan of South Korea, the Beijing 2008 Olympic Games champion, who is returning from a doping ban Sisters Cate and Bronte Campbell, who will be rivals for individual honours in the freestyle sprints, first join forces in a bid to steer the Australian team to gold, and an eminently possible world record, in this evening's climax, the 4x100m freestyle relay Two of the potential stars of the swimming programme, Sweden's Sarah Sjostrom, in the 100m butterfly, and Adam Peaty of Great Britain in the 100m breaststroke, also open their Rio accounts in today's heats and semifinals Buy your Rio 2016 tickets here