I guess by drop off, you mean less 59 / 66 HMs and 2:05 / 2:20 marathons. My guess has been that some depth is due to doping but others can run that fast clean. Anyway, it looks like it's a PED. VOX has a good explainer on it and cites to studies showing improved endurance. I can't paste the study from my phone. It seems like more than aspirin. I think a lot of people just did not know about this because it's not sold in US or Western Europe. I am pretty surprised by this. I don't recall any rumors about its benefits. Yet a bunch of athletes are on it and Boone here knew. Plus, it sounds like officials acknowledged that some Ethiopians tested positive for other PEDs. Hermens quotes were interesting too.