How to Measure Your Fitness Level

I've heard him sort of walk that back a little bit and phrase it slightly differently. I also think that when he talks about stuff like that, we often have to keep in mind that he's talking to a general population group. And so telling them to just go as hard as they can for four minutes might just be kind of his middle ground of like the best recommendation possible. But what I've heard more recently from him is something along the lines of where every four minute interval increases in effort slightly.