If you were a 12 year old with the sole goal of breaking 4 in the mile at some point in your life, would it be more effective to train to run a faster mile or to train to run 4:00 pace for longer?
Purely hypothetical of course. Let’s say you have a fairly good-for-age 12 year old that can run a 30 second 200 and a 6:00 mile. Let’s also say they live in a complete vacuum and the only thing they want to do with their life is break 4:00 in the mile at any point, whether it’s at 18 or 28 years old. If you were their hypothetical coach, would it be more effective to train them like a 400 runner until they break 60, then an 800 runner until they break 2:00, then a miler until they finally break 4:00, or should you just stick with miler training? In my mind, since you’re working with them over many years with one goal while they go through puberty, evolving the training as they develop seems reasonable, but the simple argument of “they’re a miler. Train them like a miler” definitely holds water.
(We got quite desperate for conversation topics on our long run this morning)