VO2max Explained: The Science Behind Peak Performance in Mountain Biking

Australian mountain biking history and urban myth is heavy with stories of superstars having enormous measures of VO2max. Back in the day two time World Cup cross country overall series winner Cadel Evans blew the doors off the AIS met cart (device used to measure VO2max) with his hot air balloon sized lungs. 

Surprisingly, weirdly (and sadly probably never to occur again unless it becomes an Olympic sport) Downhillers were even invited to the AIS to test their physiology. Legends of the sport Mick Ronning and Scott Sharples shocked many in the testing lab with their impressive VO2max numbers. Gossip floated around the Suntour national MTB series that they “weren’t far off the XC riders VO2 numbers”. This article contacted then head coach Damien Grundy for the actual VO2max measures of the riders but Damien remained tight lipped and Cadel, Mick and Scott’s numbers remain a mystery.  

What is VO2max? 

Over one hundred years ago pioneering scientists Hill & Lupton conducted seminal studies that still hold influence in sports science today. Hill studied runners running around his back yard and observed that the faster they ran the more oxygen they needed until a plateau in oxygen uptake occurred, not because the runner “didn’t need oxygen” but “because he couldn’t get it”. 

They could keep running or even increase their running intensity but the actual measures of oxygen they were utilising was not increasing—they had plateaued—and it is this plateau that defines VO2 max. Currently, particularly in laboratory tests the occurrence of the Vo2 plateau is crossed checked against Heart Rate plateaus, lactate levels above 8mmol mmol·L−1 and Rate of Perceived Exertion above 17 out of 20 to establish that a true VO2max plateau has occurred (Milet et al, 2023).

VO2max is described in two ways: absolute and relative. Absolute VO2max is the measure of the total amount of oxygen (O₂) you can get into the body in a minute (L/min), relative is the amount of you can get in relative to your body weight in a minute (mL/kg/min). 

Taller, more muscular riders tend to have a higher absolute VO2max, think Sam Gaze, Greg Minnar, Anika Langvad. Less tall and less muscular riders – Tom Pidcock, Jackson Goldstone, Mona Mitterwallner may have lower absolute measurement of VO2max but when measured relative to body mass the measure of VO2max may be greater per kilogram. This equals big powerful riders having an advantage on flat or rolling terrain, while diminutive riders reign on sustained climbs.  

Can VO2max be trained? 

A bit. This is where ye old trope of choosing your parents well comes into play. Training consistently over years improves the size of the hearts left ventricle and stoke volume so with every pump of the heart more blood and with it O₂ is transported to the muscles. Training also increases the amount and of mitochondria and density of capillaries in the muscle which increases uptake of O₂ from the blood into the muscle which can then be utilised to create ATP to power the body. All this adds up to a consensus that VO2 can be improved by about 5–15% (Couzens, year unknown). The limiter to VO2max training adaptations is the size of your lungs and thoracic cavity they can grow into, both of which you inherit from your old folks, mostly your Mum! 

Does VO2max predict MTB performance? 

Well…sort of. It depends which discipline of MTB and also goes into a bigger argument about VO2 as a predictor of athletic performance in sports. It seems that to perform well in sports, particularly endurance sports VO2 only forms one part of a three-part physiological equation (the mental aspect plays a role in performance as as well but this article will focus mostly on physiology). 

The three big rocks of sports performance seem to be VO2max (slightly trainable), high lactate threshold (highly trainable) and to be really efficient (highly trainable) across the terrain you intend to move across (Joyner, M. J., & Coyle, E. F. 2008).  

While it’s been identified that a huge VO2max can be helpful for predicting sport performance it’s not a the whole picture. The cyclist with the largest measured VO2 max – Norwegian Oskar Svendson with a whopping 96.7 ml/kg/min! For reference Cadel is rumoured to be mid to high 80s. 

You would assume that Svendson would dominate cycling for years to come. With a great start winning the 2012 time trial at road worlds, he never really made the cut as an U23 rider and abandoned the sport two years later. Many theorised Svendson’s departure was due to his lack of efficiency; because he had such a high VO2max he burned too many matches attacking and using his power all the time. 

Regardless, it is a great example of VO2max being a predictor of cycling success but not a the only factor. Amongst the athletes I coach for XCO those with the highest VO2max measures aren’t necessarily achieving the best performance in comparison to athletes with lower measures of VO2max and great trail skills (efficiency) achieving better performances. 

Gravity athletes I coach its seems to be the fitter they are the better their performances and also the more they train the more their results seem to improve, but this is anecdotal for now: I need to get them in the lab and start testing their VO2max to compare it to race results to get a more scientific take on this.

Overall it seems that being good across all three rocks – (VO2max, high lactate threshold, efficiency) creates the best potential for performance while being elite in one but lacking in another seems to lead to lesser performance.    

What role does VO2max play in Mountain Biking, an overview

Looking at the above chart we can see the body has a bunch of energy systems, some are extremely powerful and create a lot of energy (y-axis) but only for a very short duration (x-axis) eg ATP – PC will enable the muscles of the human body to power from motionless to extremely fast in a few seconds think at the start of a pump track race. Other energy systems burn less powerfully for longer duration: the Glycogen system can create energy for a couple of minutes and this would be the predominant energy system in a downhill race. 

And then even less energy (y-axis) but theoretically lasting infinitely is the aerobic system (VO2max) – think and XCO or XCM event; these use the glycolytic system for short powerful efforts, but the hardest working system is their aerobic energy system. 

One common misunderstanding is that the body is using only one energy system in isolation: this is never the case. It’s always using a mix of aerobic, lactic (especially for provision of energy to the heart and brain) and glycolytic to enable the body to meet the demands of the event being raced.  

VO2 max role in XCO/XCM Mountain Bike racing?  

To meet the energy demands of long distance, long duration XCO (90mins) and XCM (3hrs+) A rider with a higher VO2max uses a larger mix of the infinite supplies of aerobic energy topped up with small amounts of glycogen. A rider with a lower VO2max on the same course has access to smaller amounts of aerobic energy supply and is forced to utilise larger amounts of finite glycogen to cover the same course. Glycogen depletes sooner leaving that rider less able to do the powerful efforts (hills!) as quickly. 

They can still ride but it will be at a lower intensity and will struggle when higher intensity (more hills!) is demanded of their bodies, this is what XC riders refer to as bonking, or being cooked. Of course once glycogen is used it can be replenished through correct nutrition however the advantage of having a higher measure of VO2max in this discipline of racing can be seen in the way it saves glycogen for powerful efforts over a longer period.

VO2max role in DH and enduro Mountain Bike racing?  

The chart above shows that for the first 2mins the predominant energy system utilised to meet the energy demands of a DH/Gravity race is ATP-PC, glycogen and lactate. Most DH and enduro runs are 3mins+ so it is vital for DH and enduro riders to have a strong aerobic/VO2 system so when the race run gets past the initial 2mins of glycolytic power they have plenty of energy provision available from the aerobic system. Think back to Ronning and Sharples, both mixed DH with XC racing so had mammoth VO2max, hence no problem tapping into the aerobic system during the brutal final minutes of a DH race and maybe one of the reasons they were so good.  

On top of the DH/Gravity race demands are the pre-race demands for energy including– track walks, multiple laps in track practice and qualification runs all which repeat the process of depleting the more powerful energy systems and relying on aerobic/VO2 system. Being Aerobically fitter/higher VO2 aids in recovery between all of these things! The role of a high measure of VO2max is definitely underestimated in DH and Gravity racing. 

How should you train VO2 for XC and Gravity racing?

That’ll be in the next issue, stay tuned!