The title of this post is a forced reference to the fact that it's fucking cold now, quite suddenly. Anyway.
Matt Fitzgerald has a new book out, promoting what he calls 80/20 training. I haven't read it. But, here's a lecture from an exercise scientist discussing polarized training, which is more or less the same thing, except without a catchy name.
This more or less lines up with what is now conventional wisdom, but perhaps not conventional action. My training for the past couple years, for instance, has mostly been medium distance, medium effort. Probably not for the best. Trying to rectify that.