I've heard about this method before and so I was curious to learn more. The concept is simple: run 80% of your mileage at a low intensity Z2 pace, and 20% at Z3+ pace. The book stretches this out for a while, explaining the history of running programs, the science experiments behind the 80/20 method, how it works across different sports, etc. It gets a bit repetitive bc the author keeps hammering home how this method is the greatest thing ever. Though I am convinced, it was a bit overkill.

The important takeaway for me was that most hobby runners don't run their easy runs slow enough, and they don't run enough easy runs. I get why: if you are running 5 days a week, 4 of the 5 runs are going to be a slow jog pace. Meanwhile, commonly repeated knowledge of a running schedule is that you need a tempo run, intervals, a long run, a recovery run, and cross training, with the implication that all of that needs to happen in the same week. Then when you are trying to hit certain goal paces and comparing yourself on strava, things can get hairy, quick.

The other good thing to know if you are trying this method is that fast runners have a larger range of what slow running is for them, so it can be frustrating for amateur runner to try to stay in the target heart rate zone since the window of what is available for them is much narrower. So have patience and delete strava from your phone ;)