Let's get beyond the "drugs!" argument. It might be a valid point, but just for once I'd like to have some honest talk about the training that Salazar's group does, working under the assumption there is no nefarious pharmaceutical plot.
Salazar has developed finishing speed in at least three runners who lacked it before: Rupp, Ritz, and now Farah. In the latter two cases, they were only Salazar's charges for a few months before their big breakthroughs. And we know that Ritz had been doing prodigious endurance work under his former coaches. So I think that safely rules out an increase in raw endurance. Every runner knows that true endurance takes many months and years to develop. While I don't doubt that improving endurance improves finishing speed (indeed, this is what Rupp needs right now. It's why he can close hard against guys in the NCAA but not internationally), I do not think this is what's at play in Salazar's group.
We unfortunately don't have the luxury of Salazar posting the last few weeks of Rupp and Farah on the LetsRun Message Boards. His group operates in relative secrecy. It's interesting to contrast this with Canova, who (after the WCs) willingly posted the schedules of all his top runners for the whole world to see! So we have to extrapolate on what limited information we DO have, and rely on rumors, etc. I'm sure the LRC Rumor Mill (TM) will come through for us.
There have been several references to "lots of 200s." This probably stems from an interview with Rupp a while back (after NCAA indoors maybe?) about how he developed his finishing speed. He said something like "Alberto's had me doing lots and lots of 200s all winter." Then there was the episode where Rupp and someone else (Ritz?) caught a lot of flack for doing some 200s inside in a long, straight hallway at Nike HQ when it was rainy outside. Finally, Flotrack has a video of Rupp doing 3 sets of 600-400-300-200 quite fast (goal marks of 1:27, 58, 42, 26) during his European tour. You can watch it here:
http://www.flotrack.org/coverage/235660-workout-wednesday-season-4/video/352586-galen-rupp-workout-wednesday
Based on all the stuff Salazar says about running form, plus Rupp's extensive warmup in that workout, I imagine he also has his runners work sprint form, hip mobility and range of motion, etc.
I'd love to hear some other thoughts and if anyone has any more "sources" on what Salazar's group does in the ~3-4 months before the competitive season.