Why Workouts Are Prescribed by Duration, Not Distance

When a workout is built around hitting a specific distance, we measure it in that distance. Otherwise, we prefer duration, and there's a reason for that.

When you're training for a specific race distance, sometimes simulating that amount of time on your feet is best done by targeting a certain distance in your training as well. Track repeats, like 400s or mile repeats, are a clear example of this.

But for a lot of training, especially easy running, duration is the more honest target. A mile takes a different amount of time depending on terrain, fatigue, or how you're feeling that day. A time-based target adapts to that automatically, where a fixed distance doesn't.

Prescribing duration where it makes sense keeps the focus on effort and time on your feet, rather than turning an easy run into a race against a number.