Chances are you’ve heard the term VO2 max thrown around. Also known as maximal oxygen uptake or maximal oxygen consumption.
You probably also know that it has something to do with your endurance capacity.
But, what is VO2 max really? And more interestingly, how does it affect your cycling performance?
In order to grasp the concept of VO2 max you need to understand the basics of how your body provides the muscles with energy.
Oxygen is a substrate for fuel to the muscles
When you are comfortably rolling along the coast with the sun baking on your bare arms and legs you probably are not aware of the energy demand taking place in your muscles.
Regardless, the energy demand will be present – all muscular work requires energy.
Fat and glycogen serves as energy storages than can be tapped into whenever energy is in demand. However, your muscles cannot run on fat or glycogen directly.
Your body must first break down fat and glycogen (via glucose) to release a bundle of energy in the form of adenosine triphosphate (ATP).
Muscular work requires energy in the form of available ATP. The greatest supply of ATP to the muscle comes from breaking down fat and carbohydrates via oxidative reactions.
We can compare this process to that taking place in your car engine. For the engine to run two substrates are required – fuel and oxygen.
When this mixture ignites, the resulting increase of pressure in the cylinder drives the piston, and in turn the driveshaft and wheels.
The body works in a somewhat similar fashion. Except, instead of gas or diesel the fuel sources are carbohydrates and fat. Where the combustion engine releases energy in the form of increased pressure, the body releases energy in the form of ATP molecules.
VO2 max is a measure of your oxygen consumption
The above mentioned mechanism is essential in understanding VO2 max and how it affects your performance.
Thus far we have established that a great proportion of the energy supply to the muscles occurs via the following process (here using the oxidation of carbohydrates as example):
glucose (energy storage) + oxygen –> water + CO2 + ATP (energy)
This formula is much like a recipe for cooking – there is a fixed relationship between the different ingredients and the yield of end product.
Consequently the more glucose you burn, the more ATP you produce. However, in order to burn more glucose you also need to supply more oxygen to the equation.
It is the consumption of oxygen in this process that is calculated when you are testing your VO2 max.
As you now probably understand, the higher your oxygen consumption, the more glucose you can burn and the greater the muscular ATP supply becomes.
VO2 max tells you how much oxygen you are consuming when your burning of carbohydrates (and fat) runs at your highest possible rate. Essentially, this is a measure of how much energy your are able to supply your muscles via the oxygen-dependent (aerobic) energy system.
When you hear the terms “oxygen uptake” or “oxygen consumption”, remember that we are really talking about supply of energy to the muscles. The higher the oxygen consumption, the greater the energy supply.
How does VO2 max impact your cycling performance?
You are probably beginning to understand why a high VO2 max is beneficial.
The greater the energy supply to the muscles, the more work you can perform before reaching fatigue.
Let us try and make this more tangible to endurance performance.
A common rule of thumb is that the intensity at which your aerobic metabolism runs at 100% of VO2 max can only be maintained for approximately 5 minutes.
Typically, fatigue will be reached within 4-8 minutes at speed correlating to 100% of VO2 max. (my translation to english)
– Jostein Hallén, Utholdenhetstrening 2013
It goes without saying that the ability to provide a high power output over 4-8 minute durations are of big importance in cycling. For instance in race-winning moves and break-aways.
At the same time, cyclists often need to maintain a high level of power output for considerably longer durations. As such, they also need the ability to work at high oxygen consumption (VO2 = oxygen consumption: –> energy supply) at lower intensities.
Of particular importance is your ability to produce a high VO2 at and below your anaerobic threshold. This is where fractional utilization of VO2 max enters the picture (topic for later post).
That being said, if you have a great capacity for fuel supply at high intensity (high VO2 max), you are probably not terrible at lower intensities either.
A big engine says a lot about the potential for performance
Once again we can illustrate this with our car metaphor.
A rider with a high VO2 max is like a car with a big air intake. The air intake cannot tell you precisely how the car performs in real life. But, a big air intake is strongly suggestive of a an engine capable of consuming a lot of fuel in one go. Which in turn indicates a big engine volume and a great potential for performing work.
Still, it is not always the car with the biggest engine that wins a point-to-point race. A highly tuned 2L rally car might very well outrun a 5L american muscle car.
This because performance is more than the cylinder volume of the engine. It is also about how efficiently the engine runs at lower than max intensities (fractional utilization of Vo2 max).
Furthermore, it is also about how efficiently the work produced by the engine (muscles) is transferred to the ground (pedals) in order to create propulsion. Consider a well-tuned 4WD rally car vs. a rear wheel drive with soggy suspension.
The Bugatti Veyron has a staggering “VO2 max”. At top speed the engine consumes 45,000 liters of air per minute. This suggests a big engine (8L) capable of producing a massive work – 750 kW, or 1006 break horse powers at 6000 rpm and a top speed of 408 km/h. Still, there are plenty of cars with smaller engines and less power that would beat the Veyron in a race.
Photo: Tony Hisget.
The above argument explains why race-winning riders are not necessarily those with the biggest VO2 max. There are a lot more factors in play.
That being said, having a high VO2 max means there is also a great potential for achieving a high energy supply at lower intensities.
We can therefor conclude that a high VO2 max gives a great potential for performance. As such, a strong VO2 max will always be of benefit to a cyclist.
A note on talent identification
During the 2018 Cycling & Science conference in Nantes, I got the opportunity to ask the head of performance of a ProContinental team about their strategies for identifying talented riders.
He told me one of the parameters that gave them a lot of information in identifying future neo pros was the combination of VO2 max and fractional utilization of Vo2 max at anaerobic threshold.
The power meter equivalent of these parameters would be to look at personal best power outputs over 5 min (“VO2 max”) and 60 min durations (“anaerobic threshold”).
A desirable feature would be a well-performing rider with a high VO2 max (5 min power) and low fractional utilization (60 min power). Put shortly, if a rider is performing well despite not utilizing a great deal of his/her VO2 max there is great room for improvement.
(Anecdotal evidence suggests that fractional utilization usually has great room for improvement with increased training load over time, whereas the upper limit for VO2 max is thought to be genetically determined).
The sole point of this article is for you to understand that VO2 max is a measure of energy supply to the muscles. The higher your VO2 max, the greater energy supply and the better potential for performance.
More specifically, VO2 max represents the degree of ATP supply occurring when your oxygen-dependent energy system is running at the highest possible rate.
What VO2 max does NOT tell us is how efficiently this energy is being spent.
That is why VO2 max is an indicator of your performance potential. Other factors and physiological properties will then impact how much of this potential you are able to utilize.
This is the first in a series of articles providing insight into what physiological properties are needed to become a strong cyclist. And how to go about improving them.
Photo: Ola Morken
- Hall G. Guyton and Hall textbook of medical physiology. 13th ed. Elsevier, 2015.
- McConnell TR & Clark BA. Treadmill protocols for determination of maximum oxygen uptake in runners. British Journal of Sports Medicine, 1988;22(1):3-5
- Tjelta LI et al. Utholdenhetstrening. Forskning og beste praksis. 1. utg, Cappelen Damm Akademiske, 2014