VO2 max: How to be an over air-chiever

VO2 max is an incredibly valuable indicator for aerobic health and fitness. Put simply, this value represents the maximum amount of oxygen that the body can consume (and make use of) during maximal exertion. While you can push your body beyond this threshold, you simply cannot keep up with the oxygen demanded by your muscles to sustain the workload, and the source of energy switches from oxygen to glucose. This is an important transition, because oxygen is an easier resource for the body to get than glucose, so this switch in energy metabolism starts a timer for fatigue and exhaustion.

Essentially, the higher your VO2 max, the more your body can use oxygen for fuel. For example, if you are a runner, a higher VO2 max means you’ll be able to maintain a faster pace for a longer time before hitting an exhaustion wall.

What do my numbers mean? And how do I get them?

Traditionally, VO2 max is measured through a rather in-depth test performed in a lab. Participants will wear a mask to measure the air breathed in and out, while working on a treadmill or bike at increasing intensities until ‘max effort’ is reached. While the test itself may only take 10-20 minutes, it certainly isn’t easy! Fortunately, there are several methods to ‘estimate’ VO2 max based on submaximal exercise and activities, which can be useful for tracking and don’t require a lab visit.

It is important to understand that VO2 max can vary widely based on several factors, including age, gender, and genetics (especially muscle types). 

Even more, evaluating different elite athletes shows some differences in VO2 max among sports. Elite runners may often have a VO2 max of 60-70, while cyclists range between 65-75, and cross country skiers have a range of 75-80! Famously, Bjorn Dählie, a Norwegian cross-country skier, was able to record an incredible VO2max of 96.5 ml/kg/m!

But what does it really mean (physiologically)?

What we are really measuring here is a relatively simple equation. How much oxygen is getting to the muscle for fuel, and how much is coming out.

VO2 = Cardiac output * arterial-venous oxygen difference

Let’s break it down further. Arterial oxygen is the oxygen going into the muscle. Venous oxygen is the oxygen coming out. The difference then represents how much oxygen was used by the muscle. Next, we have to consider how much oxygen we can get to the muscle for use, cardiac output. Cardiac output can be calculated as your heart rate multiplied by stroke volume. The faster your heart pumps, and the more blood it can pump with each beat, the higher your cardiac output will be.

Can I improve my VO2 max?

When broken down like these we see multiple areas where you can find adaptations to exercise in order to improve performance. For example, over time, increases in how much blood your heart can circulate with each pump results in more oxygen delivery with each beat. (This is why well-trained athletes often have lower resting heart rates because the higher stroke volume means the heart doesn’t need to beat as much to cycle the blood around the body).

Beyond this, athletes can make changes at the muscular level to improve oxygen utilization. In the muscles, there can be changes in blood flow (more/larger capillaries or tiny blood vessels) that can improve the oxygen delivery to the muscle. Additionally, there are improvements in mitochondria (the powerhouse of the cell!) by increasing the quantity and efficiency of oxygen use as a fuel source.

To date, the best evidence for improving your VO2 max involves including a mix of interval training into your routine [4]. Improvements of 5-7% VO2 max can be achieved by adding workouts that are structured in as little as 15 seconds all out, followed by 15 seconds recovery, or longer intervals (4 minutes all out, followed by 3 minutes recovery). In these examples, ‘all out’ means 90-95% of your heart rate maximum. Regardless of how long you can maintain the ‘all out’ effort, one thing is clear; improvement can be achieved by incorporating these into your routine in a structured way.

Increasing your VO2 max is a great goal toward leading a healthier and fitter life. Not only is VO2 max associated with increased athletic performance but is also associated with longevity.

In a study comparing different levels of VO2 max and lifespan, those with the highest VO2 max experienced an average increase in life expectancy of almost 5 years! Each point increase of VO2 max was associated with an extra month and a half increase in longevity! [3]

Now, let’s all just take a deep breath… and get back out there!

TL;DR:

• VO2 Max represents the maximum amount of oxygen your body can use for energy.

• Improving VO2 Max can lead to longer efforts at faster paces.

• VO2 Max can be improved by high-intensity (90-95% max heart rate) interval training.

Sources and further reading

1. Loe H, Rognmo Ø, Saltin B, Wisløff U. Aerobic Capacity Reference Data in 3816 Healthy Men and Women 20–90 Years. PLoS ONE. 2013;8(5):e64319. doi:10.1371/journal.pone.0064319

2. Reference values for maximum oxygen uptake relative to body mass in Dutch/Flemish subjects aged 6–65 years: the LowLands Fitness Registry - PMC. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7966187/

3. Clausen JSR, Marott JL, Holtermann A, Gyntelberg F, Jensen MT. Midlife Cardiorespiratory Fitness and the Long-Term Risk of Mortality: 46 Years of Follow-Up. J Am Coll Cardiol. 2018;72(9):987-995. doi:10.1016/j.jacc.2018.06.045

4. Helgerud J, Høydal K, Wang E, et al. Aerobic high-intensity intervals improve VO2max more than moderate training. Med Sci Sports Exerc. 2007;39(4):665-671. doi:10.1249/mss.0b013e3180304570