My god. Has anyone improved as gradual as Rupp? If you are going to butcher him for a quick improvement, then everyone is fair game. He was fast in HS, a little faster in college and has progressed over many years now as a pro.
Look a little deeper at how they are training. Many of these things have been ignored (especially by North Americans) for years.
1. Increasing your weekly volume with extra non-running cardio training
2. Speed is very important for distance runners. This is something that will be questioned - especially from the (Lydiard / Cardio is the only important thing advocates.
3. Weight training - For years the aerobic first or aerobic only advocates have complained that so many runners are on steroids (which help with hypertrophy) yet can't figure out that strength training might be valuable.
4. Type of weight training - Those distance runners that did weight train did it in such a wimpy and wrong manner (huge reps rather than huge weights) that it was pretty much useless.
5. Dynamic flexibility and plyometrics - ignored by most distance runners
6. The great use of properly place aerobic intervals, fartleks, etc to increase aerobic development.
7. Spending all year (rather than just the last 6 weeks before a meet) to work on speed.
8. Technique - In the past, distance runners felt technique was useless, but Salazar has quickly figured out that is just as important, or maybe more, than it is for sprinters.
9. North American distance runners have only recently used altitude to their advantage.
So rather than yell "PED" everytime someone runs fast, take a close look at what is going on.