Olympic 400m hurldes gold medalist Karsten Warholm has warned that athletes' credibility will be tested by improvements in footwear technology.
The Norwegian shaved more than three-quarters of a second off his own world record in winning the final in Tokyo.
Silver medalist Rai Benjamin ran the second fastest time ever (46.17) in the same race, while bronze medalist Alison dos Santos posted the fourth fastest time ever (46.72).
Warholm's own Puma EvoSpeed Future Faster+ were devised in conjunction with the Mercedes Formula One team, and contain a carbon-fibre plate in the sole.
However, in the wake of the Olympic 400m hurdles final, Warholm was critical of Benjamin's Nike Air Zoom Maxfly spikes.
Benjamin's shoes contain a piece of Pebax foam which has helped him and other athletes improve their times.
"If you put a trampoline there I think it’s bullshit," Warholm said in Tokyo.
But the 25-year old has added some context to those comments, saying, "What I said was misunderstood in some way, because I had one comment about it after the race and it just blew up and that wasn't my plan at all.
"To be honest I don't know if that shoe [Nike] is the best shoe.
"My shoe is maybe just as good, but that's not what it is about, necessarily. I haven't done the science.
"When somebody does a great performance now, everybody will question if it's the shoe, and that is the credibility problem."
Warholm and his 400m hurdle colleagues weren't the only ones breaking boundaries on Tokyo's fast track.
In the women's 400m hurdles, Sydney McLaughlin also smashed the world record.
But Warholm feels the leaps in shoe technology place asterisks beside athletes' performances.
"Hopefully somebody is doing the research and hopefully World Athletics are there to protect both athletes but also the audience," he said.
"People sitting at home. I don't want them to feel like they've been fooled or tricked. I want there to be credibility.
"And that's what I feel the sport of track and field is all about. You can compare things. Yes there will always be small differences ... even though I'm all for technology pushing it a little bit forward, in all sports."
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