The Science Behind Building an Aerobic Base

How “Zone 2 training” went from temporary fad to science-backed gospel.

In the past two decades, exercise science and lab testing has caught up with the demand of endurance athletes, providing them with unprecedented knowledge about the ‘why’ behind their training. Born from this endurance enlightenment, if you will, is the widespread acknowledgment of the effectiveness of aerobic base training (aka, Zone 2 training). In this article, we’re going to dive into the science and physiology of aerobic base training and its application to endurance sports such as swimming, running, cycling, and more.  

Aerobic base training is specific training meant to increase your aerobic threshold, or your ability to perform steady-state work for a long period of time. Base training workouts are simple: go at a pace just below your aerobic threshold (the upper limit of Zone 2), and hold it. 

Your aerobic threshold is the exercise intensity at which blood lactate begins to increase substantially. Below your aerobic threshold — in Zone 1 and Zone 2 — the exercise intensity is quite low, and that’s why you can maintain these “easy” efforts for a long period of time. We’ll dive deeper into blood lactate and training zones in the next section.