Every training day is a choice. Hills, or flats? Tempo, or strength workouts? A playlist focused on Olivia Rodgrigo’s break-up, or Taylor Swift’s break-up? The best coaches are kept up late at night, thinking about how those choices influence long-term adaptation trajectories for their runners. 

As a coach, an athlete trusts you. You ask some questions and look at some data to get an athlete to reveal the initial conditions mystery: Where are they now, and where did they come from to get here? Those questions are immensely complicated, but you can usually approximate some answers. The questions that come next are why I stare at the ceiling at 2 AM.

Over time as coaches, my wife Megan and I (our podcast here!) have gathered lots of data that make the line from intervention to outcome a bit less blurry. The big two principles are what you’d expect from training theory: develop the aerobic system with plenty of easy running and/or cross-training, while building top-end output via strides and fast running. Those general elements are as close-to-universal as you’re going to get (and even they have exceptions). But what about workouts?