Best estimate I've ever been able to find, which is purely theoretical, is that juiced to the gills the top sprinters could take 0.2 seconds off their 100 times (https://nymag.com/speed/2016/12/how-much-faster-could-the-fastest-human-on-the-planet-be.html#:~:text=Conte%20puts%20the%20gain%20for,finish%20well%20under%209.50%20seconds.). The top 10 sprinters in the world last year were still >.2 seconds off of Usain's WR. None of them are going to compete because there is no upside for their careers. The next 40 are even farther off and I don't see any reason for them to compete either.

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