I've been listening to the audio book version of "out of thin air". One of the main training staples of Ethiopian runners is that they go extremely slow on their easy runs and their easy runs are over very technical and hilly terrain. So I've started to try this out. Switching from flat pavement to some technical trails. Even though my pace has gotten a minute slower per mile(though strava GAP says I'm running the same relative pace). I'm feeling much more of a workout. And I was thinking about this, if you could run slower on easy days but get the same aerobic stimulus. Wouldn't this decrease risk of injury via less stress on the body from the slower pace and having to be more dynamic on these runs(preventing overuse injuries)? And since your body is less beat up on easy days, you'll be able to have better hard workouts, resulting in faster times? So why don't more people who have access to trails in America make more use of them. Pride to say "I run my easy runs under 7 minute pace"? Who cares. What matters is how fast you run on race days. And the Ethiopians understand this, so is this one of the reasons why they are faster? Please leave drug talk off of this thread.