Aerobic Base Training: The Foundation of Successful Endurance Training

Aerobic base training, refers to a specific phase of training where the primary focus is on the development of aerobic fitness, efficiency and conditioning.

It forms a key part of any successful endurance training program. In fact, many coaches and athletes consider the aerobic base phase – sometimes called the introductory, or foundational stage – to be key to achieving peak endurance performance.

Whilst aerobic base training is used to describe the early foundational phase of an endurance training block; developing and maintaining aerobic fitness and efficiency, is actually a key part of all phases of endurance training.

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So, what is aerobic base training? And, why is it important?

Essentially, aerobic base training is a phase of training where the primary focus is placed on building a strong level of aerobic “base” fitness.

It forms the first phase of any endurance training block. In this way, it serves as the “foundational stage”, as it sets the support framework for future training blocks. And specifically, for the more intense and event specific training that will follow in the later phases of training.

As such:

developing a greater foundation of base fitness is considered fundamental for achieving peak performance.


1. Base training should focus on low and moderate intensities

During base training, the majority of training should focus on low and moderate intensities. In fact, we know that most elite endurance athletes tend to complete as much as 80% of their training at these intensities.

The rationale behind this approach is that by keeping the majority of training at low intensities, you are able to build a larger foundation of aerobic fitness, reduce the risk of injuries, and improve recovery. You will also be better conditioned for more intense and race specific training. We’ll take a closer look at the benefits of base training shortly.

2. Base training should be progressive

Whilst aerobic base training often focuses on aerobic fitness and conditioning, the overall focus is not always significantly different from other training phases. Rather, it’s the emphasis placed on certain key sessions that changes, as we move towards the preparatory and competition phases. For instance, often there is a progression towards increased race pace training, or high intensity interval training.

With base training, the progression takes the form of a gradual and progressive increase in training volume, rather than an increase in intensity. This should involve a gradual increase in weekly and monthly training volume. It should also involve a gradual progression in the volume of individual training sessions, such as your weekly long endurance run, or ride.

3. More base training = greater peak performance

The more attention you place on developing aerobic base fitness, the greater your endurance potential.

This can be better understood by considering the training phases as a pyramid structure, with base training forming the base of the pyramid. And, as you move up the pyramid we see an increase in intensity.

When viewed this way, you can appreciate how having a wider base to the pyramid (greater level of base conditioning) allows for a higher peak, or greater race performance level.

While, there are a number of different approaches used to develop an efficient aerobic base, the main emphasis is on developing aerobic fitness and conditioning.

The main difference between approaches comes down to how much emphasis, a coach or athlete, places on other areas of performance – strength, power, speed etc – during base training.

4. Intensity is still important

One important consideration is: successful endurance athletes, still include intense training during the base phase. After all, if a training method works, then why would you only use it during one phase of training?

Whilst, intense training should still feature during base training, there tends to be less emphasis on race specific training.

The key point here is:

while the emphasis may change during different training phases, you still need to include all key training elements within each phase of your plan.

In this way, it’s important to continue to work across a range of different intensities including: 

  • Submaximal intervals,
  • VO2max intervals
  • Supramaximal intervals
  • Sprint Intervals

5. Use this opportunity to develop strength

In addition to building aerobic fitness, the base phase of training is often used to develop strength and conditioning. And with good reason: the base training phase is actually one of the best phases for endurance athletes to develop strength. 

When we do this, we set ourselves for greater long term performance gains.

This can be through specific endurance focussed strength training such as hill repeats in running, or lower cadence cycling (including hills) during cycling, or using more traditional forms of strength training such as weights, circuits or core strength exercises.


The use of high-volume, low-intensity training, has a number of benefits, especially when combined with an appropriate amount of higher intensity and strength focussed training.

When done correctly, the benefits of aerobic base training include:

  1. Lower levels of physiological stress
  2. Reduced risk of injury
  3. Increased recovery from exercise
  4. Improved exercise efficiency
  5. Greater efficiency at using fat as a fuel
  6. Increased training volume
  7. Improved racing performance

1. Lower levels of physiological stress

In order for a training program to be effective there needs to be a careful balance between training stress and recovery. One feature, that is found in all successful training programs is a gradual ramping up of intensity, or training stress, across the training plan.

This is normally followed by a gradual taper, leading in to key events.

For this approach to be effective, it’s vital that athletes are able to adapt to the increasing training stresses.

With this in mind, the training stress must be sufficient to induce a training adaptation. However, the training stress must not be too high to compromise recovery. In this way, there needs to be a very fine balance between training stress, adaptation and recovery.

One benefit of aerobic base training is reduced levels of physiological stress. This allows you to gradually ramp up the training stress, by carefully and progressively increasing training volume. And by gradually increasing the training stress, we achieve a much more consistent and progressive level of adaptation – helping to ensure that you are physically and mentally prepared for the next phases of training.

It also reduces the risk of injury, illness or overtraining.

Often, we think of the base training phase as being all about logging miles.

The truth is: base training is actually more about consistent training. It’s about following a careful and systematic increase in volume. And achieving a gradual “controlled” level of progressive adaptation.

By doing this, you are better prepared and conditioned for the more physically challenging phases of training.

2. Base training reduces injury risk

Aerobic base training allows your muscles and tendons to gradually adapt to training. In fact, a key objective during the aerobic phase is to strengthen your muscles and tendons by gradually increasing training volume.

Developing strength to reduce injury risk

Reducing injury risk is not all about developing conditioning through low intensity training. In fact, developing strength in key muscle groups and tendons is one of the best ways to reduce injury risk.

So, how is this done during the base phase?

Sport specific strength training is vital

Developing sport specific strength, is a key part of the base phase of training. So, what does this mean? Put simply, sport specific strength training refers to strength training that is specific to your sport.

Running specific strength training examples

If you’re a runner then an important first step is to include regular trail running. This has a number of benefits for runners:

  • Helps to ensure that different muscle groups are worked more evenly,
  • Increases recruitment of stabiliser muscles,
  • It also develops muscular conditioning and strength through increased eccentric loading.

I’ve covered this in greater detail in an article on the benefits of trail running.

Another option is including hill repeats to develop running specific strength. Hill sprints are another great option for developing strength, power, running efficiency, and injury prevention.

While hill sprints are on the high end of the intensity spectrum, they should actually feature throughout your training block.

If you’re a cyclist, then you can look to include some lower cadence work, hill repeats and short sprints.

Traditional strength training during the base phase

As well as sport specific training, it’s important to include regular strength training to further strengthen and prepare your musculoskeletal system. While it’s common to emphasise strength training during the base phase of training; like all training types this should feature in every training block.

When it comes to strength training during the base phase of endurance training, more emphasis is normally placed on strength development rather than power development. This might involve greater focus on core strength, and fundamental exercises like squats, lunges, calf raises etc.

Having said that, the base phase of training is actually one of the best periods to develop both strength and power. And many athletes report greater long term gains by targeting strength and power during this phase.

3. Increased recovery from exercise

Another benefit of base training is an improved ability to recover from low, moderate and more intense exercise sessions. The improved recovery and ability to cope with increased training stress, may come in part from the way aerobic base training leads to improved muscular endurance and the efficient transport of oxygen and key nutrients to the working muscles (Martin and Coe, 1997; Neumann et al., 2000).

In addition, by improving the strength and durability of muscles, we also see an improved ability to cope with more intense training, and increased training volumes.

Taken together this means you are able to train more effectively, and will see greater levels of adaptation as training intensity increases.

As well as improving the rate of post exercise recovery, it also improves your ability to recover during more intense interval sessions.

What do I mean by this? Here, I’m referring to the ability to recover during the rest, or recovery periods, of interval training. This allows you to train more effectively during these interval sessions.

4. Improved exercise efficiency

Aerobic base training is considered key to improving exercise efficiency. This occurs, through a combination of:

  • Type I (slow twitch) fibre development,
  • Increased mitochondrial size and density,
  • Improved blood flow and delivery,
  • Increased efficiency of the heart,
  • Improved glycogen storage,
  • Increased levels of key enzymes.

And, not only does aerobic base training lead to improved aerobic efficiency, it sets the foundations that allows you to utilise larger training volumes and higher training intensities.

As well as improving aerobic efficiency on a cellular level, a high volume of low intensity training is believed to condition and refine the recruitment of the specific muscles used during an activity.

This works in two ways:

  • Firstly, this can improve the efficiency of the recruitment of the working muscles.
  • Secondly, it reduces the recruitment of antagonist and/or excessive recruitment of stabilising muscles (Fallowfield and Wilkinson, 1999).

Taken together, a high volume of low intensity training can improve efficiency on a cellular, and muscular level, as well as improving the co-ordination between specific groups of muscles.

5. More efficient fat oxidation

Another key feature is an improved ability to use fat as a fuel source. A key factor here, is the intensity of training.

One point to note: elite athletes don’t usually increase the percentage of time spent in low intensity training, during base training. Typically, it would still make up around 80% of total training time throughout all training blocks.

What we do see is: more of that 80% is spent at “easier” and “moderate” intensities, with less training time at steady, tempo and threshold intensities.

In this way, the training intensity is less stressful from a physiological standpoint.

Training at these lower intensities, especially when combined with longer duration training sessions, places increased emphasis on fat metabolism. Overtime, this can lead to improved efficiency of fat metabolism.

In turn, this can help to preserve valuable glycogen stores, both within training as well as during racing.

6. Increased training volumes

Not only does aerobic base training improve exercise efficiency, reduce injury risk and improve recovery from training. It also, better prepares you for the greater demands of increased training volumes and the increased use of higher intensity training (e.g. Lactate threshold training, HIIT training), that are used during preparatory and race specific phases of training.

As mentioned earlier, we often talk about the aerobic base phase of training, as being the phase of training where we log all our big miles.

In reality, the aerobic base phase of training sets us up for the larger training volumes, and the increased volume of high intensity training, used during the later training phases.

In this way, a well executed aerobic base phase of training allows for both larger training volumes and an increased volume of threshold, and high intensity interval training. This is key to successfully executing an endurance training plan.

Why training volume is important

Success in endurance sport is not all about training intensity, a key feature of the most successful endurance athletes is the use of large training volumes.

To be able to achieve such large training volumes, elite athlete complete most of their training at low intensities.

In fact, nearly all elite endurance athletes share one key feature: 80% of their total training volume (sometimes more) is completed at low and moderate intensities.

Whilst, low/moderate intensity endurance training is unlikely to lead to improvements in VO2 max in highly trained athletes (Acevado and Goldfarb, 1989; Londere, 1997); it is believed to be an important factor in long-term development.

It also plays a significant role in increasing your ability to sustain high percentages of VO2max, and for improving exercise efficiency (Noakes, 1991; Jones, 1998).

7. Improved racing performance

As mentioned earlier, the development of a strong aerobic base is considered fundamental for success in endurance sport.

Whilst this is difficult to verify through research, there are some case studies that provide insights into the importance of effective aerobic base training, for long term success in endurance sports.

From these, we can see that increased volumes of low intensity, longer duration training (typically below 2mM blood lactate, or just below the first initial rise in blood lactate), appears to be an effective training method, leading to improved training adaptations and endurance exercise performance (Seiler et al., 2009).

In particular, a large aerobic base fitness is considered key for the development of the lactate threshold, as well as the percentage of VO2max you can sustain during endurance events. It’s also a key factor in long term development, improved exercise efficiency, muscular endurance and the efficiency of Type I (slow oxidative) and Type IIa (fast oxidative) muscle fibres.

In fact, aerobic training can cause a gradual transition in type II muscle fibres, so they take on many of the characteristics of type I fibres. To the point where, after several years of specific training, these can become almost indistinguishable from type I fibres.

Summary of the Key benefits of aerobic base training:

  • Increase in mitochondrial size and density
  • Greater muscle capilarization
  • Development of efficient aerobic energy systems
  • Increased blood volume
  • Hypertrophy of slow twitch (Type I) muscle fibres
  • Increased numbers of red blood cells
  • Enhanced free fatty acid metabolism
  • Increased intramuscular fuel storage
  • Improved blood flow to working muscles
  • Increased cardiac size and output
  • Improved muscular endurance
  • Enhanced exercise efficiency
  • Stronger more resilient muscles and tendons
  • Lower levels of training stress
  • Improved functioning of muscle fibres
  • Lower risk of injury
  • Reduced blood lactate levels
  • Improved endurance exercise performance


As we’ve seen, aerobic base training is primarily focussed around low/moderate intensity training.

This raises two important questions:

  • What’s the best way to control low intensity training?
  • And what intensity is low and moderate?

Firstly, we need to define what low-moderate intensity exercise is.

What is low/moderate intensity exercise?

At the most basic level, low intensity exercise can be defined as: an exercise intensity where there is a low level of physiological stress. Consequently, moderate intensity is one where there is a moderate level of physiological stress.

What’s the best way to measure intensity?

The three main options are:

  • Heart rate
  • Power
  • Speed.

Of the three options, heart rate and power are widely regarded as the most effective.

Heart rate monitoring

Heart rate is easily measured using a heart rate monitor – generally, chest heart rate monitors are more effective than wrist based monitors – and gives a direct measure of physiological stress. Making it a great way to monitor the overall stress of a training session.

Using power to monitor intensity

Whilst power has been widely used in cycling for many years, there are now a number of devices like the Stryd footpod, that allow runners to also make use of power.

So, why use power to monitor intensity? When we combine heart rate monitoring, with power measurement, we get a much more complete picture of training intensity.

So, why does power complete the training intensity picture? Firstly, power gives you a direct measure of physical workrate (measured in watts). Secondly, power levels can fluctuate quite significantly, even when heart rate appears to be relatively constant. By giving you an instant snapshot of your workrate, power allows you to adjust intensity, before a change in workrate has a noticeable physiological effect (increased heart rate). 

In this way, monitoring both heart rate and power can be particularly effective for controlling exercise intensity:

  • Power gives a measure of work rate
  • Heart rate gives a measure of physiological stress


Essentially, we have three options, with each providing a different level of accuracy.

  1. A percentage of maximum heart rate
  2. Percentage of heart rate reserve (Karvonen formula)
  3. Percentage of estimated lactate threshold
  4. Laboratory measured lactate threshold (LT1 and LT2)

Let’s take a look at the first option: the use of a fixed percentage of maximum heart rate.

Below are the most commonly used heart rate training zones.

1. A percentage of maximum heart rate

The first approach is to use a percentage of maximum heart rate. Below are the most commonly used heart rate zones based on percentages of maximum heart rate. 

So, from this we can see that using this method why use heart rate zones? By using heart rate zones we can classify exercise based on intensity. In this way, light exercise is often classified as being below 70% of maximum heart rate, with moderate exercise being between 70 and 80% of maximum heart rate.

2. A percentage of heart rate reserve (Karvonen Formula)

We can take this one stage further by also taking account of our resting heart rate, using a method known as the Karvonen formula. In this method we first establish heart rate reserve (maximum heart rate minus your resting heart rate), we then multiply heart rate reserve by a specific intensity e.g. 70%. Finally, we add back on our resting heart rate.

While, this method is more useful than just using a percentage of maximum, it’s important to remember that this is just a guideline and doesn’t account for individual differences in fitness or conditioning. 

So, why do we also need to account for an individuals fitness level?

You only have to consider how highly trained athletes are able to train and race at much higher percentages of maximum heart rate, to appreciate how the standard heart rate training zones become less appropriate as your fitness improves.

As an example, moderate intensity might be around 80% of maximum heart rate for a highly trained athlete. In contrast, 80% of maximum heart rate could be close to, or even above lactate threshold, for a less well trained athlete. In this way, using a fixed percentage of heart rate is not always appropriate.

A more specific method is to establish training zones based on an estimation of lactate threshold.

3. A percentage of lactate threshold heart rate or power

You can make training zones more specific by estimating lactate threshold heart rate or power (FTP). This can then be used to set training zones, based on a percentage of estimated lactate threshold, FTP or race performance. We can also use time trials of field based tests to estimate lactate threshold.

One of the most straight forward tests is to complete a 30minute time trial, whilst recording heart rate and power. Your average heart rate, or power – recorded over the final 20minutes of the test – provides an estimation of your heart rate of power at lactate threshold. Another option is a cycling FTP test.

Below is an example of the training zones, based on a percentage of power and heart rate at estimated lactate threshold/FTP.

ENDURANCE56-75%69-83% LTHR
TEMPO76-90%84-94% LTHR
THRESHOLD91-105%95-105% LTHR
VO2MAX106-120%>106% LTHR

Using this method makes training zones more specific compared with using a fixed percentage of maximum.

4. Laboratory measured training zones

Whilst, we can make training zones more specific by using an estimation of lactate threshold, this is still just an estimation.

From a scientific standpoint, low/moderate intensity exercise is generally classified as being exercise that is below the first initial rise in blood lactate. This is where a laboratory based lactate test can be really useful.

Laboratory lactate testing allows you to identify two key points:

  1. The heart rate, power or speed where blood lactate levels begin to rise above baseline levels (LT1)
  2. Laboratory lactate threshold testing also identifies the point where we see an accelerated increase in blood lactate levels (LT2)

From this we can classify 3 distinct training zones as shown in the image below.

Polarised Training Zones: Aerobic Base
  • Low intensity (Zone 1): Blood lactate remains at baseline levels and doesn’t rise significantly.
  • Medium Intensity (Zone 2): There is a linear increase in blood lactate levels.
  • High Intensity (Zone 3): Blood lactate levels increase at an accelerated rate.

Identifying the first rise in blood lactate levels (LT1), allows you to better control low and moderate intensity exercise. When exercising below LT1 (Zone 1), exercise is largely fuelled by the aerobic metabolism of fats with only a relatively small contribution from carbohydrate metabolism. Training within this zone allows you to complete large training volumes with a significantly lower risk of overtraining.

Training in Zone 3 (above LT2), has also been shown to be highly effective. It’s also considered more productive than zone 2 training. 

Using this information, you can then optimise training intensity.

Using a polarised training approach

As I mentioned earlier in this article, most elite athletes complete 80% of their training at low intensities, with approximately 15-20% at higher intensities. In fact, the intensities they use are often based around LT1 and LT2; with 80% of training below LT1 (in zone 1), and a further 20% completed at higher intensities. 

Often, the higher intensity training is split into 5% in zone 2, and 15% zone 3. Although, this will vary depending on your training focus. As an example, a marathon runner would spend more training time in zone 2, compared with a 10k runner. 

This approach to training is often referred to as “polarised training” and has been shown to be a very effective way to optimise training. 

So, by identifying these key training intensities you can make better use of your training time, improve recovery rates and reduce the risk of overtraining.


  • Aerobic base training involves training at low to moderate training intensities – typically 65-75%HRmax (running), or, 60-70%HRmax (cycling).
  • Training at these intensities involves the recruitment of slow twitch (type I muscle fibres)
  • A large portion (>50%) of any endurance based training programme should be devoted to aerobic base training. However, most elite athletes devote 80% of total training time to these intensities.
  • Aerobic base training has a number of advantages including: 1) reduced levels of physiological stress; 2) lower risk of injuries; 3) improves post exercise recovery; 4) enhanced exercise efficiency; 5) improved efficiency of fat metabolism; 6) allows larger training volumes; 7) leads to improved exercise performance. , 
  • Aerobic base training helps to prepare the body for the physiological demands of higher training intensity training.
  • The relatively low intensities utilized during aerobic base training allow athletes to complete large training volumes with a reduced risk of overtraining, when compared with higher intensity training (>LT)
  • A large volume of aerobic base training appears to be particularly important for the development of the lactate thresholdexercise economy, fatigue resistance, mitochondrial size and density, enhanced aerobic energy pathways
  • Aerobic base training is best monitored using heart rate or power.
  • Training intensity can be controlled using a percentage of maximum heart rate, percentage of estimated lactate threshold, or laboratory measured lactate values.
  • Laboratory testing is particularly effective, allowing you to control training based on the relationship between intensity and blood lactate levels.
  • A polarised training approach – involving large volumes (80%) of low intensity training, combined with 15-20% of higher intensity training – appears to be particularly effective.

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Aerobic Base Training References:

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Londeree, B.R. (1997). Effect of training on lactate/ventilatory thresholds: a meta analysis. Medicine and Science in Sports and Exercise. 29, 837-843.

Martin, D.E. and Coe, P.N. (1997). Better Training for Distance Runners (2nd edition). Human Kinetics: Champaign, IL, USA.

Neumann, G., Pfutzner, A. and Berbalk, A. (2000). Successful Endurance Training. Oxford: Meyer and Meyer Sport (UK), LTD.

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