The body type of world class 100m competitors is due to genetics and steroids. Sprint workouts don't make people muscular. Muscular guys gravitate towards those events. Also, HIIT workouts are nothing like what 100m runners do to train.

You can be pretty sure that marathon runners are using PEDs too.

PED drugs yes, anabolic steroids no

The primary effect of anabolic steroids is to reduce recovery times. Bodybuilders get so big on them not because they magically make you bigger but because they let you train incredibly hard.

Long distance runners do use anabolic steroids amongst other PEDs. [1]

"For example, Lyubov Denisova tested positive for Prostanozol and Testosterone in 2007. She has won the Honolulu and Los Angeles marathons and has been 2nd place at New York."

Prostanozol is an anabolic steroid.

[1] http://www.runningahead.com/forums/post/d63143aa7f5246359388...

I am aware of the effects of AEs

In fact, the regimen of muscle fatigue/recovery is different between endurance sports and 'strength' sports

A marathonist is not limited by his/her muscle mass. A strength athlete is.

Yes, some marathonists may use AEs, but it's much rarer than other PED (like EPO, HGH - which also helps with recovery, blood doping, etc)

Prostanozol is actually a "prodrug" (yes, it is an AE). "Prodrug" usually means more liver damage and less results than a proper AE cycle (as it's called) and there are better alternatives.

I love interval training. Whether it's a highly-structured protocol (maybe Tabata) or more of a Fartlek approach, it's a blast. The approach I find to be both a lot of fun, and very productive, is to do a sort of Fartlek approach (with, say, running, or working on the elliptical trainer) where I put my ogg player on "shuffle" and let the song dictate my intensity. Certain songs ("Kickstart my Heart" by Motley Crue for example) just demand extreme exertion... other times you get something a little more chill ("Lights" by Journey, maybe) where you just cruise for a while.