VO₂ max

Contents

1. Introduction
2. What is VO₂ max?
3. Why is VO₂ max important? 
4. What is the VO₂ max formula? 
5. How to measure VO₂ max
6. What is a good VO₂ max?
7. VO₂ max normative data
8. How to increase VO₂ max
9. Conclusion

Introduction

Sport and exercise scientists use the term VO₂ max to determine cardiovascular fitness. VO₂ max allows us to quantify aerobic fitness by calculating maximal oxygen uptake during aerobic activity, usually by running on a treadmill or cycling on a cycle ergometer.

What is VO₂ max?

VO2 max, or maximal oxygen consumption, refers to the maximum amount of oxygen that an individual can utilise during intense or maximal exercise. In other words, VO₂ max refers to the maximum amount of oxygen your body can absorb and use during exercise.

VO₂ max is like our body’s version of an engine in a car. A larger engine can generally burn more fuel and produce more power. Similarly, a higher VO₂ max allows the body to utilise more energy and have a larger aerobic capacity. 

Let’s look at the term VO₂ max (or V̇O₂ max) and break it down:

• ‘V̇’ stands for rate of volume over time (as indicated by the  ̇). Often written with ‘V’ instead.
• ‘O₂’ stands for oxygen 
• ‘max’ stands for maximum.

Put these words together and we get something along the lines of ‘maximum volume of oxygen uptake’ – essentially VO₂ max is the maximum volume of oxygen our body can consume and utilise and it is generally considered the best indicator of cardiovascular fitness and aerobic endurance.

Why is VO₂ max important?

When we exercise hard, there is an increased demand for oxygen in our muscles. Therefore, the more oxygen we can consume and utilise, the easier the exercise feels to our body. VO₂ max is measured in millilitres of oxygen per kilogram of body weight per minute and is shortened to ml·kg^-1·min^-1.

History of VO₂ max

British physiologist Archibald Vivian Hill is recognised as a pioneer when it comes to VO₂ max. In the 1920s, Hill and colleagues began a series of experiments that collected air samples and analysed oxygen and carbon dioxide concentrations while subjects exercised (1). From these experiments, they discovered there was a relationship between exercise intensity and oxygen consumption (2). 

In the 1950s, research by Henry Taylor and colleagues further established appropriate protocols for measuring VO₂ max (3). During the 1960s, normative data published by Per-Olof Åstrand, and Bengt Saltin showed VO₂ max data across a range of sports – there was a significant relationship between high-level endurance performance and high VO₂ max from the normative data collected (4). From this point on, it became clear a higher VO₂ max represented a higher level of aerobic fitness. 

What is the VO₂ max formula?

VO₂ max was traditionally measured using Douglas bags, however indirect calorimetry is the preferred method nowadays (5).

The Fick principle states that the amount of O₂ consumed by the body (VO₂) is equal to the amount of O₂ leaving the lungs (Q̇T)(CaO₂) minus the amount of O₂ returning to the lungs (Q̇T)(Cv̄O₂) and is calculated as follows:

V̇O₂ = (Q̇T)(CaO₂) – (Q̇T)(Cv̄O₂) = Q̇T(CaO₂ – Cv̄O₂)

This formula is used by the algorithm in the programme which runs the breath-by-breath gas analyser to calculate VO₂ max (6).

How to Measure VO₂ max

A VO₂ max test is the gold standard test for measuring oxygen uptake as it directly measures body oxygen consumption. Many other tests estimate VO₂ max, whereas a VO₂ max test provides an accurate VO₂ max. Theoretically, the test can be performed using any exercise mode, but it is typically performed on a treadmill or cycling ergometer. However, using the most specific mode for the athlete and their sport is usually the best option. For example, it would make more sense for a rower to perform the test on a rowing machine rather than a treadmill, if it was available. 

Throughout the test, the participant wears a fitted mask, which is connected to a gas analysing machine. This machine measures the amount of oxygen being inhaled and exhaled. During the test, the exercise intensity will gradually increase until the athlete stops or until their oxygen consumption plateaus. If oxygen consumption plateaus, it indicates the participant is no longer using oxygen to break down energy and instead is relying on anaerobic (without oxygen) metabolism. 

It is worth noting a VO₂ max test is a maximal test that requires an appropriate level of fitness. Therefore, caution must be taken if it is being used with recreational exercisers or people with underlying health issues. See the following for a video of a VO₂ max test being performed.

What is a good VO₂ max?

A relative VO₂ max is expressed in millilitres per kilogram per minute (ml·kg^-1·min^-1). According to the American College of Sports Medicine (2014), the average for a 20–29 year-old female is 38 ml·kg^-1·min^-1, while it is 44 ml·kg^-1·min^-1 for a 20–29 year-old male (7). Using the female average as an example, a result of 38 ml·kg^-1·min^-1 means there are 38 millilitres of oxygen per kilogram of body weight being utilised per minute. To be in the 90^th percentile, a VO₂ max of 47 ml·kg^-1·min^-1 for a female and 54 ml·kg^-1·min^-1 for a male is required. 

Aerobic capacity is needed for many sports, but some sports have a higher demand than others. Data collected by David Nieman (presented in the NSCA Essentials of Strength Training and Conditioning) illustrates VO₂ max guidelines based on the sport (8). For example, power sports like shot put, javelin, discus throw, and Olympic weightlifting don’t have a high demand for aerobic capacity. Therefore, the average VO₂ max listed earlier may suffice for these sports. Court sports like basketball, volleyball, and tennis are very much anaerobic sports but do require some aerobic capacity, so an above-average VO₂ max is needed. Therefore, a VO₂ max of 44-48 ml·kg^-1·min^-1 for females and 52-56 ml·kg^-1·min^-1 for males is recommended. 

Sports like soccer require a high VO₂ max and it is recommended for females to have a VO₂ max of 49-53 ml·kg^-1·min^-1 and 57-62 ml·kg^-1·min^-1 for males. Sports like long-distance running, skiing, and cycling are heavily reliant on aerobic capacity. Therefore, it is recommended that female athletes have a V̇O₂ max of 60+ and male athletes 70+. 

What is the highest ever recorded V̇O₂ max?

In March 2010, a 15-year-old Swedish boy named Oskar Svendsen, who had transitioned into cycling from skiing, was trying out for the cycling program in his local high school and took part in the required VO₂ max test. He recorded an impressive 74.6 ml·kg^-1·min^-1. Svendsen had only just transitioned into cycling and his previous skiing training consisted of one to two workouts per week. To record such a high value, as a virtually untrained 15-year-old, highlighted his incredible potential. It also highlighted how much of a role genetics plays in aerobic capacity. 

Fast forward to August 27, 2012, the now 18-year-old Svendsen would take the crown of the ‘greatest oxygen user’ from Dæhlie, recording the highest ever recorded V̇O₂ max of 96.7 ml·kg^-1·min^-1. Unlike Dæhlie, Svendsen’s VO₂ max has been mentioned in scientific literature. In fact, he was used as a case study in a scientific published paper (9). The paper referenced how in just three years of dedicated training, he went from an individual with little aerobic training exposure, to a junior champion time trial cyclist. Unfortunately, the paper also mentioned with 15 months of detraining, his VO₂ max returned to 77 ml·kg^-1·min^-1, because after two years after becoming a junior world champion, Svendsen quit cycling. 

It is reported Svendsen went back to university to study psychology. However, his incredible VO₂ max is still referred to as the highest ever recorded. The following table is a timeframe of Svendsen’s VO₂ max is referenced in the published case study paper (9). It is worth noting how high his VO₂ max naturally was without training but also how much higher it got with training. 

Table 1. Oskar Svendsen Reported VO₂ max Testing History (7)

Alternative Aerobic Tests

The VO₂ max test is the gold standard, providing an accurate result of maximal aerobic capacity. However, it is relatively time-consuming and expensive to conduct. Therefore, there have been many alternative aerobic tests developed that are more practical, cheaper, and time efficient. It is important to understand these alternative tests only provide an estimation of a VO₂ max based on the test result. 

Tests such as the Bruce Protocol Stress Test, the Astrand Treadmill Test, and the Vmax Test are just some alternatives to the VO₂ max test. These tests require the athlete to progressively exercise until voluntary exhaustion without requiring the fancy equipment used in VO₂ max test. The final values on these tests are then inputted into a predictive equation to provide an estimation of VO₂ max. Although they are a cheaper alternative, they are not directly measuring VO₂ max and caution must be taken when interpreting results. 

For field sports, cost and time-efficient tests such as the Beep Test, the Yo-Yo Intermittent Recovery Test, and the 30-15 Intermittent Fitness Test are often used to measure aerobic capacity. These tests require the athlete to run repeated bouts of shuttle runs to voluntary exhaustion, then the athlete’s value is imputed into a predictive VO₂ max equation and an estimated VO₂ max is provided. Unfortunately, there is inconclusive research on the accuracy of predictive VO₂ max equations for these tests. 

Research from Magee et al. (2021) found four commonly used predictive equations for the Beep Test overestimated VO₂ max (10). Interestingly, the researchers did find the Ramsbottom and Flouris equations may provide a close estimate of VO₂ max. Research from Yiannis et al. (2020) found that V̇O₂ max estimated in a Yo-Yo Test equation was significantly different to the actual VO₂ max measured in the laboratory (11). There is some evidence by Stankovic et al. (2021) that the 30-15 Intermittent Fitness Test can provide an accurate estimation of VO₂ max. However, the authors of this systematic review did note there was an insufficient lack of studies comparing the estimated VO₂ max to an actual VO₂ max recorded in the laboratory (12). 

Smartwatches and mobile apps now generally provide VO₂ max, but are these VO₂ max readings accurate? Research from Synder et al. (2021) found the popular Polar V800 to provide random errors of up to 16.4 ml·kg^-1·min^-1 for VO₂ max prediction (13). The researchers did find the Garmin Forerunner 230 to be slightly more accurate, but it did consistently overestimate VO₂ max. Earlier research from Passler et al. (2019) found the Garmin Forerunner 920XT and the Garmin Vivosmart HR failed to show valid results in estimating VO₂ max (14). 

For Fitbit lovers, research from Soon Bin Kwon et al. (2019) showed that Fitbits only provided a moderate estimation of VO₂ max (15). Some of the research has proposed that the heart-rate measurements obtained for the wrist sensors are inaccurate, therefore leading to an inaccurate VO₂ max prediction. Let’s remember a phone app or a watch isn’t connected to your lungs, whereas an oxygen mask used in a VO₂ max test is.

VO₂ max normative data

Following adequate screening and testing guidelines should ensure individuals are safe to take part in maximal testing. To ensure athlete development is appropriate, VO₂ max testing can inform programming to develop aerobic capacity.

Table 2. Percentile values for maximal oxygen uptake (ml·kg^-1·min^-1) (7).

How to increase VO₂ max

It is important to understand that VO₂ max is largely determined by genetics, sex, and age. Research by Williams et al. (2017) suggests that VO₂ max trainability is approximately 50% determined by genetics (16). There is also a sex difference associated with aerobic capacity, though this is less a sex difference and more a difference in the capacity of physiology and training status, as demonstrated by elite female athletes and their significantly higher VO₂ max than most men (17). 

So though there is a significant difference in VO₂ capacity between males and females, this is small when compared to other factors such as the dimensions of the oxygen transport system and lean muscle mass (18). Age also affects VO₂ max – Hawkins and Wiswell (2013) have shown that after the age of 25, VO₂ max decreases by around 10% per decade (19). 

So, if genetics, sex, and age play a significant role in aerobic capacity, is training to improve VO₂ max a waste of time?  This is arguable. Let’s look at Svendsen again. After embarking on his cycling career, his VO₂ max increased from 74.6 to 96.7 ml·kg^-1·min^-1. After 15 months of detraining, his VO₂ max returned to 77 ml·kg^-1·min^-1, very similar to before he started cycling. This illustrates despite having incredible genetics, VO₂ max is significantly changeable with training. Genetics might limit aerobic capacity but without training, an athlete is never going to reach their limit.

Improving  endurance:  VO₂ max isn’t everything

It is worth noting that even in endurance-based sports, other factors such as lactate threshold and exercise economy are equally or perhaps even more important than VO₂ max. In his book ‘The Science of Running’, renowned author Steve Magness provides examples of dramatic improvements in performance by world record holders and Olympic champions, despite little to change in their VO₂ max (20). Changes in exercise economy or lactate threshold might be plausible explanations for the improvements. 

First, let’s discuss exercise economy. Exercise economy is how much oxygen our body needs to exercise (run, cycle, swim, row etc.) at a particular pace. Let’s use two marathon runners as an example. Both are running at the same pace but Runner A has a higher exercise economy than Runner B. Runner A is more economical with oxygen and can do more than Runner B with the same amount of oxygen. Therefore, Runner A will be able to sustain the pace for longer than Runner B almost ensuring Runner A’s success.

Lactate threshold is the point at which blood lactate levels increase above resting levels. Having a higher lactate threshold will allow an athlete to exercise at a higher intensity for longer. Again, during any race, this is essential to improve overall time and possible medal contention.

There are many different types of aerobic training used today. There is often much debate about which form of training is best to increase VO₂ max, with a meta-analysis by Milanovic et al. (2015) finding both traditional endurance training and interval both can improve VO₂ max (21). Traditional aerobic training is commonly referred to as Long, Slow Distance (LSD) training. LSD is a method used in endurance training. This type of training is approximately 30 minutes+ in duration at a pace of approximately 70 % of VO₂ max or 80 % of maximum heart rate (HRmax). The pace is relatively easy and therefore this training method is completely aerobic. Building this aerobic base will help the body become more efficient at using oxygen and recovery during more intense endurance training methods. 

Interval training is a more intense training method often aimed to increase VO₂ max. Interval training comprises of work-to-rest intervals. Work intervals should be close to VO₂ max and last 3-5 minutes. It takes at least two minutes to reach your VO₂ max, so this time range exposes the body to work at this high intensity. Intervals longer than five minutes will cause too much fatigue and exercise form may deplete. The rest intervals are normally the same time as the work intervals, allowing the body a chance to recover before the next work interval. Guidelines for LSD and Interval training were taken from the NSCA Essentials of Strength Training and Conditioning (22). 

Conclusion

A higher VO₂ max is certainly crucial for successful performance in endurance sports. But even in endurance-based sports, other factors like lactate threshold and exercise economy may be equally or even more important than VO₂ max. Having a high VO₂ max certainly helps but does not entirely guarantee success either. Let’s not forget Svendsen, and how there is more than just one ingredient needed for success at the top level. 

For many field and court sports, sufficient aerobic capacity plays a critical role in success, too. It is no surprise to see many sports include aerobic testing batteries and training programs. But don’t forget, these field tests don’t measure VO₂ max, they just provide an estimation! So next time someone asks you how aerobically fit you are, you now know how to answer, and even if you don’t know your own VO₂ max, hopefully you can explain what VO₂ max is.