Aerobic Base training

Aerobic base training forms a key part of successful endurance training. When we talk about aerobic base training we are normally referring to a phase of training where the primary focus is the development of aerobic fitness, efficiency and conditioning.

Many coaches and athletes consider this aerobic base phase of training – sometimes called the introductory, or foundational stage – to be key to maximising performance during an endurance training program.  

However, it’s important to remember that throughout all training phases a large proportion of training is actually devoted to low intensity basic aerobic training (referred to as Zone 1 and Zone 2 training – if you are familiar with training zones). 

So, whilst aerobic base training is used to describe the early foundational phase of an endurance training block, in reality all the training phases of an endurance program focus the majority of training time on developing aerobic fitness and efficiency. And, as we move through the phases of a plan – from aerobic to preparatory to the competition phases – we change the emphasis and intensity of training sessions.

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

What is aerobic base training?

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

As discussed above, whilst aerobic base training is often used to refer to a specific phase of training, the overall focus is not significantly different from other training phases. 

The aerobic base phase forms the first phase of any endurance training block. And, in this way it’s viewed as the foundational stage as it sets the support framework for the rest of the training block – specifically for the more intense and event specific training that will come in the later phases of training.

The rationale behind this approach is that by building a large foundation of aerobic fitness, we are better conditioned for more intense and race specific training. 

This approach views the training phases as a pyramid, 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, the wider the base of the pyramid, the higher the eventual peak – or race performance level – will be.

There are a number of different approaches used to develop an efficient aerobic base. However, 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, speed etc – during this base phase of training.

One important consideration is that successful endurance athletes, still include more intense training during the base phase. If a training method works, then why would you only use it in one phase of training? 

Whilst, the emphasis may change during the plan we still need to include all key training elements within each phase of the plan.

What are the benefits of aerobic base training?

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. 

Low intensity training plays a key role in the development of basic endurance. And, whilst the emphasis is placed on this during the base phase of training, it should still make up a significant proportion of the total training volume throughout a training plan.

When done correctly, aerobic base training has a number of benefits, including:

  1. Lower levels of physiological stress
  2. Reduced risk of injury
  3. Increased recovery from exercise
  4. Improved exercise efficiency
  5. More efficient 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 key to all successful training plans is a gradual ramping up of intensity, or training stress, across the training plan. This is followed by a gradual taper leading up to key events. For this to be effective it’s vital that athletes have time to effectively adapt to training stresses.

Aerobic base training places a lower level of physiological stress on athletes. This allows the athletes to gradually adapt to the training and ensures they are physically and mentally prepared for the next phases of training.

Whilst we often think of the base training phase as being all about logging miles. When done correctly base training is more about consistent training that follows a careful systematic increase. This prepares you for the more physically challenging phases of training.

2. Reduced risk of injury

Aerobic base training allows our muscles and tendons to gradually adapt to training. A key objective during this aerobic phase is to strengthen the muscles and tendons by gradually increasing the training volume.

If you’re a runner then an important factor is to include regular training over undulating terrain, as well as off-road running. This helps to ensure that different muscle groups are worked more evenly. 

Including some hill reps is also important. Short hill sprints can feature throughout the training block. And, are particularly important for efficiency, running form and injury prevention.

As well as basic endurance training, it’s important to include regular strength training to further strengthen and prepare the musculoskeletal system. 

Whilst, it’s common to emphasise strength training during the base phase of training, like all training types this should feature in every training block. The main difference with base training is that more emphasis should be placed on strength development than power development. In this way strength training during the aerobic base phase, should concentrate more on core strength, and fundamental exercises like squats, lunges, calf raises etc.

3. Increased recovery from exercise

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

In addition, by improving the strength and durability of muscles we see an improved rate of recovery and ability to cope with both more intense training, and increased training volumes. Taken together this means we are able to train more effectively and see greater adaptation as training intensity increases.

As well as improving the rate of post exercise recovery, it also improves our ability to recover during more intense interval sessions – such as during the recoveries between interval sessions.

4. Improved exercise efficiency

Aerobic base training is considered key to improving exercise efficiency. Not only can aerobic base training lead to improved aerobic efficiency – 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 and improved fuel storage and increases in key enzymes – it sets the foundations that allows you to utilise larger training volumes and higher training intensities.

This is important since we know that as well as intensity, a key feature of most successful endurance athletes is the use of large training volumes. And, in particular large training volumes made up of a significant amount of low intensity training (~80% low intensity). 

Whilst low/moderate intensity endurance training is unlikely to lead to improvements in VO2max in highly trained athletes (Acevado and Goldfarb, 1989; Londere, 1997) – the use of large-volume low-intensity training is believed to be an important factor in long term development. And, plays a significant role in increasing our ability to sustain high percentages of VO2max, and for improving exercise efficiency (Noakes, 1991; Jones, 1998). 

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, and; secondly, reducing 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 at using fat as a fuel source

Another key feature is an improved ability to use fat as a fuel source during exercise. Here a key factor is the intensity of training. Firstly, elite athletes don’t actually increase the percentage of time spent in low intensity training (Zone 1 and Zone 2 training zones) during base training – typically, low intensity training still makes up around 80% of total training time. 

What we do see is more of that 80% spent at the lower end of zone 2 – often the longer workouts may cross over between upper zone 1 and lower zone 2.

Training at this intensity, especially when combined with longer duration training sessions places increased emphasis on fat metabolism. Overtime this can lead to improved efficiency of fat metabolism. 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 both increased training volumes and the increased use of higher intensity training (e.g. Lactate threshold training, HIIT sessions), used during preparatory and the race specific phases of training. 

We often talk about the aerobic base phase of training as being the phase of training where we log all our big miles. However, 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 more intense training. This is key to successfully executing an endurance training plan.

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 do provide some insights into the importance of effective aerobic base training for long term success in endurance sports. Here, increases in low intensity longer duration training (below 2mM blood lactate – typically just below the first rise in blood lactate) is considered to be an effective training method, leading to improved training adaptations and endurance 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 that can be sustained during endurance events. In addition it is likely to key to the long term development or exercise efficiency and improved muscular endurance and efficiency of both Type I (slow oxidative) and Type IIa (fast oxidative) muscle fibres.

Summary of the Key benefits of aerobic base training:

  • Increase in mitochondrial size and density
  • Increased 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
  • Low level of training stress
  • Improved functioning of muscle fibres
  • Reduced risk of injury
  • Reduced blood lactate levels
  • Improved endurance exercise performance

Training types used during the aerobic base

As you would expect the focus of training during aerobic base training is primarily around low intensity aerobic training – typically what we know as Zone 1 and Zone 2 training. 

The percentage of training time devoted to building an aerobic base (zone 1 and zone 2 training), shouldn’t differ significantly across a whole training plan. Although, we would typically see a slight decrease in the average intensity of these sessions so we work at the lower end of Zone 2. And, sometimes during long training sessions the intensity may be between upper zone 1/low zone 2. During later stages of training – such as pre-competitive training – upper zone 2 training is generally favoured. 

During base training we can use this slightly lower intensity to develop a good level of base conditioning, and enhance fat metabolism. Importantly, this intensity allows us to complete longer duration endurance training sessions with lower levels of physiological stress.   

One advantage here is the reduced physiological stress which allows us to increase our total training volume. This increase in overall low intensity training volume, is considered important for endurance exercise performance and long term training adaptations (Seiler et al., 2009). Another advantage is the increased emphasis on fat metabolism which helps to preserve valuable glycogen stores.

So what training intensity should you use for low intensity training? 

The main training methods used when you build your aerobic base fitness:

1. Aerobic Base Recovery training (Zone 1)

Typically Zone 1 training is typically used for recovery sessions after harder training sessions. Although sometimes longer duration training sessions combine upper zone 1 training with lower zone 2 training, to place greater emphasis on fat metabolism

Zone 1 Training Running Cycling
%Heart Rate Max 65-75% 60-70%
Heart Rate Reserve 60-70% 55-65%

2. Aerobic base endurance training (Zone 2)

Zone 2 aerobic training makes up the bulk of endurance training, and is responsible for most of the training adaptations discussed earlier in this article. 

Zone 2 Training Running Cycling
%Heart Rate Max 75-85% 70-80%
Heart Rate Reserve 70-80% 65-75%

3. Longer base endurance training sessions (Zone 1/Zone 2)

Longer duration training sessions can be run across a range of training intensities depending on. the phase of training. However, during the base phase of training these are typically low Zone 2 training sessions. And, sometimes this may be between upper zone 1 and low zone 2 – especially during longer bike sessions. 

Zone 1/Zone 2 Training Running Cycling
%Heart Rate Max 70-80% 65-75%
Heart Rate Reserve 65-75% 60-70%

In addition to building base aerobic fitness, the base phase of training is often used to develop strength and conditioning. This can be through highly specific training such as hill reps 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.

As well as low intensity and strength training, it’s still important to use some higher intensity training during the base phases of training. Here it’s important to work across a range of different intensities including submaximal intervals, VO2max and Supramaximal intervals. The key point here is that the volume of specific higher intensity intervals should be lower than during the pre-competitive phases of training. However, they should still feature as part of every phase of training. 

Aerobic base training summary:

  • Aerobic base training involves training at low to moderate training intensities – typically 70-85%HRmax (running), or, 65-80%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) it places a lower level of physiological stress; 2) it reduces the risk of injuries; 3) improves post exercise recovery; 4) It leads to improved exercise efficiency; 5) It increases our efficiency of fat metabolism; 6) It allow larger training volumes; 7) It 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 References:

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