Fears expressed over current in Olympics Aquatic Centre swimming pool
Researchers and commentators are concerned a current in the Olympic Aquatics Centre swimming pool affected the Rio 2016 competition.
Olympic medallist and BBC commentator Andy Jameson posted a link to the research on Twitter and wrote it was "very worrying if true".
Jameson, a 100 metres butterfly bronze medallist at Seoul 1988, wrote: "Very worrying if true! A current circling around the Olympic Pool? Re-swim!
"Crystal Palace pool had it but an Olympic pool definitely should not! Shockingly unfair for those swimming upstream!"
The research, posted on swimswam.com by Barry Revzin, looked at split times per length of the 50 metres pool and used data from the last two World Championships, in Barcelona and Kazan, plus recent United States competitions, for comparison.
Olympic-sized swimming pools are 50m in length and 25m wide, enough room for 10 lanes, although only eight are raced in at a major event.
Swimmers say if they have a lane they have a chance in a race and expect there to be no difference.
Seedings - from entry, heat and semi-final times - determine that the quickest swimmers race in lane four, then lane five, lane three, lane six and so on, with the slowest qualified swimmer in lane eight.
But research suggests there may have been an issue at the 2013 World Championships and in Rio with assistance from the pool.
"Barcelona and Rio were dramatically different," Revzin wrote.
"In both pools, there was a clear drift from lane one to lane eight - which suggests that swimmers were pushed towards the start end in the upper lanes and pushed towards the turn end in the lower lanes, with the effect greater the further you get from the centre. This is very concerning."
The prospect of drift or a current - caused by the circulation of water from the filtration system - and the difference it makes was starker in the 50m events. At Olympic level the only 50m event is 50m freestyle.
Revzin added: "These results are very disconcerting to me, but do not in and of themselves prove that there is a problem.
"However, the data strongly points to serious problems in the pool which could have led to an unfair competitive environment, especially in the 50m freestyles. I think it should be investigated."
Press Association Sport has contacted FINA, swimming's world governing body, and Rio 2016 for comment on the research.
The swimming competition at the Olympic Aquatics Centre finished last Saturday, with Britain winning a modern Games best of six medals - one gold and five silvers.
Pernille Blume of Denmark won the women's 50m freestyle, where the top six swimmers, racing between lanes three and eight, finished within 0.12 seconds.
Anthony Ervin of the United States won the men's event from lane three by 0.01secs.
The pool is now hosting the final rounds of the men's and women's water polo competitions.