VO₂ Max: A Fundamental Metric Of Cardiovascular Fitness And Distance Running Performance?

Many endurance runners have a natural curiosity about VO₂ max testing and wonder whether it is worth the hype. Physiological tests like this are usually conducted in a university exercise physiology lab, national Olympic training center, or some other elite athlete service center. If you are paying for it yourself, the test might cost a few hundred dollars. And the service is not usually well-advertised, which leads to a feeling of exclusivity around the whole thing.

But I think it’s great for runners to be interested in physiological testing. Everybody wants to have the best chance to succeed according to their potential. If I had the ability to provide everybody with elite-level sport science support, I would. The goal of Distance Running Lab is to educate and provide as much service as possible through this website and associated media. I am glad when runners of all levels put in the effort to learn about their own physiology and use that information to better their performance.

[Disclaimer] This article is about oxygen consumption related to distance running performance and not cardiovascular disease. If you are seeking information about oxygen consumption in the context of a medical condition, please contact a licensed medical professional.

What does VO₂ max mean?

Let’s start with VO₂ (without any “max”). VO₂ is the rate of oxygen delivery to working muscles. There is a measurable VO₂ when you are at rest and this can increase up to 20 times or more for the very fittest individuals.

During rest and exercise alike your lungs inhale air and take up the oxygen. This oxygen is delivered via the blood first to the heart and then it is pumped to the working muscles. The muscles then accept this oxygen and can use it to make energy via the oxygen-dependent metabolic processes.

More intense exercise uses up energy faster, so the rate of oxygen delivery increases too. You can feel this with increased breathing and a faster heart beat. Eventually the intensity becomes so much that the oxygen-delivery system reaches its maximum.

Exercise physiologists like to debate the reason for this limit – and whether there is a limiting factor in the lungs, heart, blood, blood vessels, muscle cells, or some combination of the above. More holistically-minded exercise scientists also remind us that the contribution of the brain and nervous system recruitment are also vastly important.

Whatever the reason for this limit, it is true that every individual has a maximum VO₂ value that can be measured. Above your maximum oxygen consumption, energy needs require  anaerobic metabolism, which means rapid fatigue. Since endurance running performance depends mostly on oxygen delivery, a higher VO₂ max is better, all other things being equal. So, does it help to know your VO₂ max? And how should you use that information?

What does VO₂ max really tell you?

The question of how to use this information is an important one. Here are a few reasons that I think runners have for wanting their VO₂ max tested:

1. It will tell me my ultimate potential in running.
2. It will tell me what I need to work on in my training.
3. It will tell me how to set proper intensity training zones.

Let’s go through each of these.

Does VO₂ max indicate distance running potential?

Short answer: yes and no.

If you take a large group of people across the population, the group will include people of all shapes and sizes, all levels of performance, and all levels of training experience. In such a group, the individuals with the highest VO₂ max will be the best runners.

In other words, there will be a nice straight-line relationship: those with the lowest VO₂ max will run the slowest and those with the highest VO₂ max will run the fastest.

However, if you take a group of well-trained distance runners, you will no longer be able to separate the winners using VO₂ max. There is a well-known study from the 1970s where elite distance runners from the United States were tested in a physiology lab.

This group included Steve Prefontaine (VO₂ max ~84 ml/kg/min) and Frank Shorter (VO₂ max ~71 ml/kg/min). Both Prefontaine and Shorter were Olympians, but Shorter’s VO₂ max was 15% lower. If VO₂ max were the only determinant of distance running success, Shorter would not even be in the same league.

So, in a group of similar runners, VO₂ max will probably not distinguish the fastest from the slowest.

Will a VO₂ max test identify areas for improvement?

Perhaps, but the benefit may be limited.

The goal of any sport science testing should always be to lead to actionable insights. In the case of aerobic fitness, even without a VO₂ max test, we already know of the importance of aerobic fitness and training to improve it.

No matter whether you have a poor or excellent VO₂ max, you are still going to train your aerobic system. And your training program will already be set up so that you train specific paces, according to your goal race distance.

For example, both 800 m runners and marathoners need to have a high VO₂ max, but the principle of specificity suggests that the 800 m runners will spend more time at VO₂ max pace than will marathoners, who must spend more time accumulating miles at the slightly slower speeds associated with anaerobic and lactate thresholds.

If you want to fully understand the best areas for improvement, see how your different race performances rate according to the method I demonstrate in this article. If your performances score lower at shorter or longer distances, then you might alter your training intensity emphasis to focus on these specific ranges.

Will knowing my VO₂ max help me define my training zones?

Yes, but there may be a more convenient alternative.

The thinking is that VO₂ max is important and the best way to train it is to run at that pace, therefore you need to know your VO₂ max. It’s true that training zones can be nicely defined by different percentages of VO₂ max. If you take this approach, I am confident that you will be training at the proper mix of intensities – sometimes at your aerobic maximum, sometimes at lower percentages during recovery runs.

But you are training for a good race, not a physiological test. Since that is the case, I recommend that you view your training zones relative to race pace instead of a physiological metric. This approach uses a table like the one below. NOTE – it is not possible to precisely state the different zones for any individuals. These are approximations, and you won’t get this information from a lab test unless you first conducted a VO₂ max test and then another test of how long you can run at different percentages of VO₂ max.

The example table above is based on a study by sport scientists in Portugal, in which the participants had an average 3000 m time trial of 9:03. They were thus able to run at about 100% of their VO2 max pace for about 9 minutes.

Notice that I emphasized the word pace. I did this because I don’t want to suggest that their physiology was working at 100% VO₂ max for that whole 9 minutes. It takes a bit of time to accelerate oxygen consumption, so the first few minutes would be at a lower percentage of that max. You can run at the pace for the whole time. But you can’t run at that physiological intensity the whole time.

The duration different individuals can run at each percentage VO₂ max is not always the same. Some runners might last a few more minutes than others at the same physiological intensity. Keep in mind also that if a runner underperforms on a VO₂ max test (i.e., quits early), the reported maximum will be lower and the time lasted at each intensity might be longer (because it’s easier).

Even when conducted at a laboratory, the imprecision and nuances of a VO₂ max test means that any recommendations that come from that test are only approximate. It doesn’t mean that they are wrong, only that it may mean that other methods may provide a similar benefit.

It’s good to want to improve your aerobic physiology because that is how you will eventually run faster. I think that you can ensure the proper mix of intensities by employing a multi-pace system based on the different race distances. But for those who wish more formal guidance, a VO₂ max test can provide that.

Does my running watch measure VO₂ max?

No, your running watch cannot measure your oxygen consumption. I would love for that to be the case, but measurement of oxygen consumption requires you to breathe through a mask or mouthpiece. The device measures the oxygen going in and out when you breathe and the difference between in and out is what your body has used.

A running watch predicts VO₂ max based on information it does have – heart rate and running speed. Those data are put into a prediction equation to estimate your VO₂ max. These prediction equations are created by testing many people and comparing the watch data to actual VO₂ data collected in a laboratory.

Where to get a VO₂ max test

Unless you are in a national program for elite sport, a VO₂ max test will most likely be conducted at a university exercise physiology laboratory or medical system that offers sports performance services.

You can try searching for the following departments that might exist at a local university: “sport science”, “exercise science”, “exercise physiology”, “human kinetics”. To search for services offered in a medical system, just search for the name of your local hospital and “sports performance”.

Preparing for a VO₂ max test

First, the test needs to be a running test, as a VO₂ max can be measured for many endurance sports such as cycling. While there are aspects of cardiovascular fitness common to all modes of exercise, it is crucial that your test is a running test.

The simplest reason is that you need to know how to push yourself in the exercise you are performing. You will not be able to give your best cardiovascular effort during cycling if you primarily run.

When you arrive for your test, you will probably complete some forms regarding your medical history and sign a liability release. If you have any cardiovascular condition, but are still cleared for exercise and do it regularly, the staff will definitely want to see that documentation from your doctor.

Some labs will require you to fast overnight and avoid caffeine prior to the test. The reason is that ingestion of different proportions of carbohydrates, fats, and caffeine can alter metabolism. Although this is true, I don’t agree that this should be a requirement. Overnight fasting may not represent normal habits, and if not, you would be doing the test in a way that is unnatural to you. If you enroll for a VO₂ max test as part of participation in a formal research study, however, any nutritional pre-test controls won’t be negotiable.

You want to be able to give your best effort, so treat your preparation like a race. Avoid fatiguing training in the day(s) before the test and sleep and eat as you normally would.

One criticism I have about testing is that the time and space for a full warmup is usually not provided. You will definitely be provided the opportunity to warm up on the treadmill prior to the beginning of the test, but you probably won’t be able to duplicate everything you commonly do on the track or trail. You might ask if you may warm up on your own outside if it is convenient.

One last aspect to prepare for is that you be very comfortable with strenuous running on a treadmill. The test requires you to continue running until you can’t continue. If you are worried about falling off the treadmill at high speeds (while wearing a breathing mask), you will most likely stop before you have truly given your maximum effort. This is crucial because I believe many people underperform simply because they are not used to the test.

What happens during a VO₂ max test?

A VO₂ max test is an incremental test which means that it starts slow and increases the intensity at regular intervals. There are many protocols for how the increases take place. You should ask your testing staff what protocol they use.

For running, the protocol should increase speed only and not the incline. If the incline increases, the most strenuous part of the test will be done with a significant uphill, which doesn’t allow for a normal assessment of running speeds, heart rates, etc. Perhaps the treadmill will be kept at a 1% incline to counteract the absence of wind resistance with treadmill running.

The protocol I favor is the one used in this scientific paper (Noakes et al., 1990). It starts at 12 km/h (7.5 mph or 8 minute mile) and increases by 0.5 km/h every 30 seconds until you can’t continue. The idea is that you will continue for several minutes at least, so if you are a slower runner and the starting speed is too close to your max, you might start the test at 10 km/h or 8 km/h instead.

There are other protocols that may have longer intervals like 1 minute long, and protocols where the speed might increase in increments of 1 km/h.

The testing staff will encourage you to give your best (probably by yelling!). They will remind you to safely hold on to the treadmill when you are done and will help you remove the breathing mask or mouthpiece. This will be a messy time because of accumulated saliva!

How is a VO₂ max test analyzed?

The measurement device monitors several physiological variables at once:

• The oxygen you consume
• The carbon dioxide you produce
• Your heart rate
• Your running speed

From these variables, the staff will be able to report your maximal oxygen consumption. This will typically be in the last stage you complete. You might continue running a few stages past that and demonstrate a plateau in VO₂, but not everybody shows that.

The staff may also provide your anaerobic threshold, which is an intensity lower than VO₂ max. Anaerobic threshold is a catch-all term associated with rapid increases in breathing and blood lactate variables. The existence of a precise threshold is debated in the scientific literature, but the concept associated with sub-maximal aerobic fitness is sound. You also want this to occur at a relatively high running speed and a relatively high percentage of VO₂ max. It correlates to performance at the longer distance like half marathon and marathon.

How to train VO₂ max

It is possible to improve your VO₂ max, VO₂ max pace, and the duration you can maintain that speed. It is generally accepted that the best stimulus to improve VO₂ max is running at about that pace.

In the example above, the runners were able to run at about their VO₂ max pace for about 9 minutes. Interval training splits up the distance, which lessens the strain and makes it possible to still accumulate a lengthy time spent at VO₂ max.

Here is one method by French researcher Veronique Billat to accumulate time at VO₂ max using very short intervals according to time:

• Option 1: 15 seconds @ 90% VO₂ max pace alternating with 80% VO₂ max pace.
• Option 2: 15 seconds @ 100% VO₂ max pace alternating with 70% VO₂ max pace.

A total accumulated distance (including fast and slow) might be 4000-5000 m. Workouts like this that involve very short intervals can maximize the time you spend at VO₂ max (the physiology, not the speed). With longer intervals, there might be an inefficient use of time as your engine speeds up and slows down with every interval.

Remember, however, that even though it is good to consider how much time you are spending in a physiological zone, when you are running at a certain speed, your are still in a specific biomechanical zone, meaning that your leg muscles are still propelling and landing as part of your running gait. That neuromuscular action is also something that needs to be trained.

With this perspective, one considers all the benefits from an interval session, not just the oxygen-related ones. One possible workout that might emphasize the pace more than the physiological intensity is:

• 16 * 400 m @ 3000 m race pace with 45 seconds rest

The above allows for the accumulation of 4800 m of running at that pace. The distance is more than 3000 m, but the intervals are relatively short. It is thus much easier than:

• 8 * 800 m @ 3000 m race pace with 60-90 seconds rest

The first workout (16 reps) is easier because each interval has a relatively easy portion at the beginning. This occurs only half as often when doing 8 reps only. The latter workout would “hurt” more near the end of each interval, which can be desirable when attempting to simulate the challenge of an actual 3000 m race.

You can also try interval lengths of up to 5 minutes or so (perhaps 3 reps), and the distance will vary with your own running speed. This would emphasize the red-hot intensity of a 3000 or 5000 m race. This workout would be very stressful, so you would need to be in good shape.

Over the course of a season, you might emphasize the physiological zone first and then maintain the physiology while you train the race pace per se as race-ready sharpening occurs.

VO₂ max and body weight

For running, VO₂ max is properly expressed per kilogram of body weight. This is because running is a weight-bearing activity, in contrast to cycling. For every kilogram of body fat lost in a healthy manner, and maintenance of cardiovascular function, VO₂ max will automatically increase. For example, with a 5 kg fat loss:

• Before: VO₂ max = 40 ml/kg/min @ 70 kg
• After: VO₂ max = 43 ml/kg/min @ 65 kg

This will result in an increase in performance, all other things being equal. But don’t make the mistake of thinking that mere weight loss improves your cardiovascular fitness. Rather, the benefit occurs because the same cardiovascular function now can carry a lighter individual.

Summary

VO₂ max is a popular point of discussion by runners interested in exercise physiology and peak performance. It is definitely part of what makes a good distance runner, but its predictive value is not great in a group of similar runners. If you want a well-balanced training plan, run at high percentages of your VO₂ max, along with easy days for recovery. For the most part, your training zones can be estimated from your pace in the different race distances.

This is a good approach because you are most likely most interested in a good race time instead of high physiological values! By doing this, your cardiovascular system will be challenged and your running-specific neuromuscular action will also be trained. Remember that peak performance is achieved when all systems work optimally!