By Uphill Athlete co-founder Scott Johnston
Max VO2 is the Holy Grail of endurance qualities, right? Looking at the fitness landscape, you’d sure think so. Many training methodologies embrace it as the metric that rules all others, and the popular media fuels this misunderstanding with articles about how to boost your max VO2 in order to be the best athletic you. But of the three main components that pertain to endurance—economy, speed at lactate threshold (aka anaerobic threshold), and max VO2—max VO2 correlates the least with performance.
During my ski racing career, in which I was a World Cup also-ran, I was tested several times for max VO2. I always tested with a higher max VO2 than the other US Ski Team guys I raced against who routinely placed in the top ten and occasionally even in the top five in World Cup races, much better than I ever did. That’s when I began to question the validity of the assumption that max VO2 is a predictor of performance, and I sensed that something else was holding me back. Years later, I pinpointed that weakness: economy, especially at racing speeds; Economy is a metric that didn’t even figure into training 35 years ago.
Later on my long-burning questions about max VO2 turned into full-blown skepticism of the models that place this quality on a pedestal above all others—and often to the detriment of others.
I have personally trained athletes with low max VO2 values who have been quite successful at the World Cup level. I have also trained athletes with maxVO2 numbers in the stratosphere who were not competitive at he World Cup level.
A real life story
Before I worked with him, one of these skiers had been the recipient of huge financial and material resources from the US Ski Team over the course of five years, years that were devoted almost exclusively to improving his max VO2 at the expense of other aspects of his training. He did max VO2–protocol interval sessions three times a week, and his max VO2 was tested three or four times a year. The net effect of this myopic approach was essentially zilch. There was no change in his vaunted max VO2 value, and his race performance stagnated. Eventually he lost his spot on the team.
He was 30 when he came to me for training, and I told him it was fruitless at this late stage to attempt to change his max VO2. “You’ve been a professional athlete for most of your life now,” I said. “You’re stuck with whatever sized engine you’ve got.” It didn’t matter that we couldn’t supercharge his engine; instead, we worked on his economy so that it would cost him less energy to go at race pace. The next year, he was the fastest guy in the country. He went from being kicked off the team to winning major races.
A common definition of insanity is doing the same thing over and over while expecting different results. All it took to change the game for this skier was shifting the focus of his training.
A Little History
A scientist named A.V. Hill was the first to figure out that work limitation is oxygen related. Back in the early 1920s, Hill ran around a grassy field with a big balloon—a Douglas bag—to collect his exhaled air. Then he sampled the bag’s CO2 content to determine how much oxygen he used in the time he was running. He observed that as he increased intensity, his oxygen uptake would eventually plateau. He called this maximum rate of oxygen consumption his max VO2
Hill’s discovery offered the first verifiable explanation for the limits of human performance, and it stuck.
A high max VO2 is an undoubtedly valuable tool to have in your arsenal of endurance qualities; successful endurance athletes often have very high max VO2 values. But we may be confusing cause and effect. Current popular understanding embraces max VO2 as the metric that governs and limits performance. But I believe that in reality max VO2 is the effect of performance, not the cause. It is a measure of the body’s maximum sustained power output, analogous to your car engine’s horse power. A car with poor aerodynamics will require more of its maximum horse power to sustain a give speed. We say that car has poor fuel economy. A runner or skier with poor technical economy also requires more aerobic power to maintain a give speed.
With both a car and an athlete it is handy to have one metric to describe performance. Car companies frequently tout the power of the engines in their cars as selling points. The 300 horse power car must surely be faster/better than the 250 horsepower car. Right? In reality performance is too complex to be defined by one number and is often governed by several interconnected and even competing factors.
MaxVO2 gets tossed around in the endurance athletic press like horsepower does in car magazines: “My engine’s bigger than yours.” This has led the lay public to a misunderstanding of the concept of maxVO2 and led to an undue emphasis on training to improve that quantity.
How We Got Here
Many exercise science studies of training protocols use max VO2 as the measure of their success or failure. Why? Because it’s easy: It’s a relatively straightforward metric to isolate, measure, and compare across studies. But that does not mean maxVO2 is the best proxy for athletic endurance performance. Another fly in this ointment is that these studies typically recruit untrained subjects . Among the untrained and young people, max VO2 is likely to increase rapidly regardless of the training protocol. MaxVO2 is what is called a “first-wave response”: if you take someone who is not very aerobically fit and give them any sort of exercise, max VO2 is one of the very first things to improve. After about four months, however, it plateaus then responds much less significantly to training stimuli. The change in the subjects max VO2 from week one to the final week “determines” if the test protocol works. If max VO2 goes up, it’s a success! The program improves maxVO2. But does it improve endurance performance?
The heart muscle is super trainable up to a point largely determined by your genetics. High-intensity interval training (HIIT) at above 90% of maximum heart rate is the most effective training method for improving max VO2 in the short term. That’s because the heart when taxed to near maximal responds by getting stronger and more elastic: it ejects more blood (greater stroke volume) which means more oxygen going to the muscles to power more work. But the heart is surrounded by a sheath of relatively inelastic fascia called the pericardium, beyond which it can’t expand. Once the heart reaches this point where it can’t expand more, stroke volume plateaus as does maxVO2.
What does this imply for the well trained endurance athlete? First thing is that your ultimate maxVO2 is probably significantly determined but genetics. If you have a history of HIIT your maxVO2 is probably at or approaching your personal genetic limit. You may need to look at other ways of improving your endurance performance.
A Real World Example
Several long-term longitudinal studies(1) of elite endurance athletes have shown that max VO2 values don’t rise at all—and in some cases decline—despite the athletes’ showing improved performances from year to year. During a taper phase in preparation for a big race, max VO2 typically drops due to the reduced training volume, but performance increases despite the drop.
As an example of this effect in a real world high level amateur athlete we want to use our very own Scott Semple who has kept meticulous records of his training and has had several maxVO2 tests conducted before he was being coached by me and continuing to the current time. Scott has written several articles on this site about is personal transformation from a severely aerobically deficient Skimo wanna be to qualifying for the Skimo World championships this year. His careful record keeping demonstrates perfectly the observations I allude to above.
What this graphic demonstrates so clearly is that Scotts maxVO2 (the turquoise line at the bottom) declined 11% between the age of 31 and 39 and remains 7% below his age 31 peak. Since beginning structured Skimo training his maxVO2 has risen only 4% but his performance (as indicated by his paces; the red and blue lines) has improved dramatically. Something other than the small change in maxVO2 must have played a role in his performance improvement.
Max VO2 is clearly not a neat-and-tidy measure of endurance, so why does the general exercising public continue to mistakenly embrace it as just that? Look no further than zingy headlines that equate boosting your max VO2 with guaranteed performance returns—headlines that over-inflate the importance of this single number and distort the bigger endurance picture.
Here’s the reality, especially as it pertains to the people we coach at Uphill Athlete: You do not need a monster motor to summit a Himalayan peak or run an ultra. No one races 50 miles or climbs a mountain while operating at their maximum capacity; you can only hold that effort for a few minutes. Besides, there’s so little oxygen at high altitudes that it’s physically impossible to operate anywhere near your top-end intensity. These pursuits demand endurance, which is the ability to sustain a sub-maximal workload for a long time—over multiple hours or even days. You’re not going to be running five-minute miles at 8,000 meters.
Max VO2 is just one of several things that goes into accounting for endurance: it might set your upper limit, but it doesn’t have much to do with how you perform at a sub-maximal level. So instead of fretting that you do not have a world class max VO2, focus instead on optimizing your aerobic base, and improving your economy. When it comes to long-duration events, these are the things you can most influence that will improve your performance.