Put simply, your VO2 max is a numerical measurement of your body’s ability to consume oxygen at the maximal sustained output. 

It’s not something that’s fixed – it can be affected by your red blood cell count (which can be impacted by, for example, spells at different altitudes), how efficient your muscles are to the variations in the oxygen ‘supply & demand’ requirements of your chosen sport, and how much blood your heart can pump with every beat. Additionally, age & gender will have an impact.

Research says VO2 is about 80% genetic and the other 20% is trainable.

The best riders have high VO2s genetically, AND can push it higher with training. For untrained people, VO2 Max can be increased by as much as 10%, just by getting fit, as an unfit person can improve their cardiovascular conditioning as their heart gets bigger & stronger through exercise – you essentially improve the part of the oxygen supply chain enabling you to move more blood and therefore get more oxygen to the muscles. However, everyone will have an inherent genetic limit, thus the No.1 rule for success in endurance sports applies: choose your parents carefully!

THE VO2 MAX TEST

In a laboratory, it is calculated by measuring the volume (V) of oxygen (O2) that you consume while riding a static bike on a turbo trainer – In the VO2 max test, you’re hooked up to a breathing mask while you undergo progressively more difficult demands (i.e. pedal faster / increased resistance).

Your VO2 max occurs when your oxygen consumption redlines. At this point, your heart rate is also at its maximum.

After doing a simple calculation involving your rate of oxygen consumption during the test and your body weight, you’re presented with a number that expresses how much oxygen you were consuming whilst pedaling at your hardest, per kilo of body mass.

WHAT ARE NORMAL NUMBERS FOR A MAX VO2?

In most people, it will be somewhere between 40 and 70. The units are milliliters of oxygen per minute per kilogram of body weight (ml/min/kg). The more oxygen your body can absorb, the more power it can produce. A Grand Tour winner will likely have a number in the mid to high 80s. Chris Froome’s claimed VO2 max numbers have ranged from 80.2 – 88.2, depending on changes in his weight. So, as an amateur, if you have a VO2 Max of 50, you probably shouldn’t hold your breath for a Pro Contract.

WHAT DOES HAVING A VO2 MAX NUMBER MEAN?

All else being equal, a higher VO2 max is a good thing: it means that your body can take in more oxygen and deliver it to your muscles, enabling you to ride faster for a given effort.

However, when taken by itself, VO2 max is not very helpful, because your ability to process oxygen is only half the equation when it comes to how fast you can ride.  The other half is how efficiently you put that oxygen to use.

Among groups of amateur cyclists with the same VO2 max, you’ll see a wide variety in their performances. While elite cyclists do indeed have very high VO2 maxes, the ones with the highest VO2 max aren’t always the fastest, since a high VO2 Max doesn’t necessarily mean high power-to-weight. In elite cycling, your power-to-weight ratio (expressed in Watts per Kilogram of body weight) over various durations (e.g. 10, 30, 60 seconds, 1, 10, 60 minutes) is in most cases more crucial than VO2 Max. Therefore, if you maintain the same ability to process oxygen, but lose some weight, your VO2 Max measurement will increase.

Crucially, pro riders are more concerned with what % of their VO2 Max (if they even have that number) they can sustain & for how long because to get up and over mountains, they must be able to sustain as high a power number as possible. The effort or power output at VO2 Max is something that you can’t sustain; it’s not fully aerobic. But trying to get the percentage no. of your FTP [functional threshold power] closer to your VO2 max is where the improvement lies. For example, take someone with a VO2 Max of 75 who can only do 60% of that at FTP, versus someone with a VO2 Max of 70 who can do 75%. That latter person will outperform the former.

Elite riders like Froome possess both extraordinarily high VO2 Max numbers and highly aerobically sustainable power outputs.

Finally, for time trialing, Power-to-drag is also important. Making our frontal area as small as possible will help overcome the largest resisting force of all: air.

TRAINING TO IMPROVE VO2

To understand how VO2 can be improved, or not, training it helps to understand what oxygen consumption means. Think of VO2 Max as the supply-and-demand of oxygen, transporting it from the lungs to the muscles. Things that affect that are how well your lungs function at moving oxygen from the air into the blood, the stroke rate and volume of your heart, and capillary density. The demand is the rate at that your muscles call for oxygen, a mitochondrial process.

In the blood-doping era, EPO raised the VO2 Max of users because it increased the oxygen-carrying capacity of their blood.

So, any aerobic training, even just riding at zone two [roughly 60-74% of threshold power] will help train VO2 Max. The most effective thing though is to do intervals at an intensity that elicits VO2 Max. I.E. go hard enough so that your body hits the point where it is processing as much oxygen as it can, and then stay at that point for as much time as possible – riding at VO2 max effort is a great way to improve your VO2 max.

A classic VO2 Max workout (great on a turbo trainer!) is 6 x 5 minutes @110-120% FTP with 3-4 minutes recovery. The limited recovery time means you don’t recover completely, and thus get more time at VO2 Max. In that workout, it will generally take about two minutes of the first interval to reach VO2 Max, meaning you’re getting three minutes at VO2 Max. But subsequent intervals will only take the 90s or less to reach that state, so more of the interval is spent at VO2 Max. 

If you’ve done a VO2 Max test, then you’ll have a very good idea of what your heart rate training zones are & can use these to determine at what % of your VO2 you are training at. Else, there is a standard test you can do to determine your heart rate zones.

Once fit, improving your VO2 Max becomes exponentially harder. For most amateur & many elite athletes, testing for VO2 Max doesn’t serve much purpose. However, knowing what your power at lactate threshold / FTP is can be much more beneficial & can be trained/monitored/improved much more easily.