Aerobic Base Training: The Science of Success

Endurance athletes have long understood the effectiveness of aerobic base training, or Zone 2 training, for achieving peak performance. While training in all zones is necessary, aerobic base training is a key part of any successful training plan as it not only improves overall levels of fitness but also prepares the body for more challenging workouts later on. It’s often overlooked by a number of athletes or approached in the wrong way without the data to set appropriate training zones.

This article explores the physiology and science behind aerobic base training and its importance within endurance sports.

What Is Aerobic Base Training?

Aerobic base training aims to increase your aerobic threshold – which is your ability to maintain steady-state effort for a long period of time. The exercise intensity below your aerobic threshold (Zones 1 and 2) is quite low and so by holding a pace that is at the upper limit of Zone 2, the aerobic threshold can be increased, and activity can be sustained over a long period of time.

In essence, the focus is on building a substantial level of aerobic ‘base’ fitness.

Endurance athletes such as marathon runners will include aerobic base training as a consistent part of their training in order to prepare for the physiological demands placed on the body during events that can last for many hours.

Aerobic Threshold Vs Anaerobic Threshold

I’m sure you’re aware that aerobic means “with oxygen” while anaerobic means “without oxygen”.

During aerobic effort, such as endurance events, the body primarily uses oxygen to generate energy as part of the oxidative system and so heart rate and breathing rate increase to supply more energy to the muscles. Anaerobic effort, such as a sprint, involves a short, intense burst of activity whereby the body breaks down glucose stores to use as the primary energy source, rather than oxygen.

Your aerobic threshold is the intensity at which blood lactate begins to rise above resting levels.  Blood lactate is linked with muscle fatigue and so when exercise intensity increases above the aerobic threshold, the body is unable to clear blood lactate as quickly and fatigue sets in.

Raising your aerobic threshold allows you to maintain activity for longer as less build-up of blood lactate occurs and so you experience less fatigue and exhaustion. During anaerobic efforts, your muscles fatigue quickly due to a fast build-up of blood lactate. This means that anaerobic activity can only be sustained for a few minutes, even by highly-trained athletes.

Aerobic base training is often referred to as “Zone 2 training” as when your energy output and heart rate are maintained in Zone 2, your blood lactate concentration will stay below the aerobic threshold.  

What Makes a Good Base Training Plan?

Increasing fitness and adequate recovery time are both important components of a successful base training plan. These can be achieved with a balanced training schedule that includes an element of high intensity exercise, such as HIIT (High Intensity Interval Training), that will target both your aerobic and anaerobic thresholds.

Here’s an example of a good base training plan:

  • Weekly volume increases of 5-10%
  • 1 or 2 long endurance sessions (>2 hours)
  • 1 or 2 HIIT sessions
  • 1 rest day
  • Rest week every four – six weeks (complete rest or decrease the weekly volume by ~50%)

This plan incorporates a gradual increase in workload, or progressive overload, to improve fitness and structured periods of rest to reduce the risk of injury or burnout. At the base phase of training, the focus is on consistent training and aerobic endurance rather than high intensity activity.


Understanding the basic principles and science of aerobic base training is one of the best indicators of performance in endurance sports. Training your aerobic threshold is more important than training your anaerobic threshold when aiming to maintain a low blood lactate over long periods of time and therefore improve your endurance performance. The higher your aerobic threshold, the further and faster you will go.

A good training plan for endurance athletes includes long sessions of Zone 2 training, along with some HIIT sessions and strategic rest days.

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