Usain Bolt, whose 9.58 seconds world record for the 100 metres is now 16 years old, says he could have run 9.42 in the carbon-plated "super-spikes" that today's sprinters are racing in.
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The Jamaican set his mark at the 2009 world championships in Berlin, breaking his own 9.69 record from the previous year's Beijing Olympics, and it has now stood for longer than the 14 years of Jim Hines's 9.95 set at the 1968 Mexico City Olympics.
Research by Puma, the company that shod him through his glorious era of dominance, predicted that Bolt would run 9.42 in today's shoes and, speaking at an event ahead of the world championships in Tokyo, he said: "I fully agree."
"Someone who continued after I retired was Shelly-Anne Fraser-Pryce and I saw what she did - she got faster with the spikes," Bolt said on Thursday.
"I probably would have run way faster if I'd continued and if I knew that spikes would have got to that level maybe I would have, because it would have been great to compete at that level and running that fast."
Bolt's compatriot Kishane Thompson ran 9.75 at the Jamaican championships in June - the fastest time by anyone for 10 years to make him the sixth-fastest of all time - but Bolt said he was not worried about anyone breaking his record anytime soon.
"I think the talent is there and those who are coming up will do well but, at this present moment, I don't think they will be able to break the world record," he said.
Bolt retired in 2017 with six Olympic and seven world individual 100m and 200m golds, and no Jamaican man has won a global sprint title since his Rio Olympic double in 2016.
Thompson came within five thousandths of a second of ending the drought when he was pipped on the line by Noah Lyles in last year's Olympic 100m final and Bolt says he, or compatriot Oblique Seville, could go one better in Sunday's 100 metres.
"I think we have a very good chance this year. Kishane and Oblique have really showed this season that they're really doing extremely well," Bolt said.
"I'm looking forward to it, I mean they should be one-two because they've proved they are running fast times so it's just all about execution. So I'm happy to go into the stadium and see and hopefully I'll be able to present the gold medal to one of them."
'DIFFERENT BREED'
Tokyo will be the first global athletics event Bolt has attended since his farewell at the London world championships in 2017, though whether he presents the medals is likely to depend on who is doing the receiving.
Bolt might find himself otherwise engaged if it is defending champion Lyles on the top step.
He said he has no issues with the American, despite having a social media spat with him a few years back, and despite Lyles getting under Jamaica's skin by announcing that he had Thompson "in his pocket" earlier this season.
"I don't think Noah is as crazy as dealing with Justin (Gatlin), so for me it's no different," Bolt said of his former rival.
"I think Gatlin over the years, we pushed back and forth, but he was a different breed because he came up in the era where trash talking was just normal to everybody.
"As you know I never listened to anybody, I know when I'm preparing and I'm ready you can say whatever you want you're not going to beat me so I'm always focusing so it would never be a problem."