Poland back in the 60’s under Gerard Mach. Much better than the Russians. The only top sprinter to come out of the Soviet Union was Borzov, and as Charlie has mentioned a few times, Borzov did not follow the official training system and was resented by the top officials for it.
Polish sprint training “secrets”? Definitely. Soviet sprint training secrets? Myth.
Even setting aside Charlie’s methods, as Charlie himself has stated in a post years ago, if people simply used the methods Gerard Mach and Bud Winter were using back in the 60’s they would get much better results than the “high tech” crap that has become popular over the last 20 years.