Is VO2 Max Dead?

A controversial researcher says the key to speed and delayed fatigue lies in your brain, not in your lungs.

Tim Noakes is a South African scientist and medical doctor who likes to ruffle a lot of feathers. His controversial theories are famous for challenging conventional wisdom on topics ranging from sports medicine to biomechanics to nutrition, like promoting a high-fat, low-carb diet for the general population. But perhaps his most game-changing idea is one that rethinks why athletes slow down.

“The Central Governor Model merely says that the brain regulates exercise performance to ensure that you do not die during exercise,” Noakes says. It seems simple, but the idea rejects a popular view that performance is limited by our ability to use oxygen during intense exercise, a measure known as VO₂ max.

In the past, VO₂ max testing has been considered a predictor for athletic performance—the higher the VO₂ max, measured as milliliters of oxygen processed per minute per kilogram of bodyweight, the faster the athlete. It’s generally thought that at peak VO₂ max, athletes begin to slow down because their muscles go anaerobic due to lack of oxygen.

But Noakes says if the body’s muscles were limited by the amount of oxygen they could use, the first thing to fatigue when an athlete is exhausted would not be their legs; it would be their heart. They’d experience severe chest pain, similar to the feeling of an oncoming heart attack, which is what occurs when the heart muscle actually does go anaerobic. We know that we can feel terrible during exercise, but not every workout or race ends in a life-threatening chest spasm.

Furthermore, he says, while VO₂ max might be a good indicator of peak speed during the test itself, often there is not a direct correlation between VO₂ max and fast racing. For example, 1969 marathon world record holder, Derek Clayton, had a VO₂ max score of 69.7 ml/min/kg, whereas Craig Virgin, a slightly slower marathoner from the same era had a much higher VO₂ max score of 81.1 ml/min/kg.

With those points in mind, Noakes inferred that something else is causing us to slow down when exhausted, well before a lack of oxygen—something like a speed regulator in a car that prevents us from going too fast and killing ourselves.

That regulator, Noakes says, is our brain. Noakes says the brain subconsciously stops recruiting muscles in order to create the feeling of fatigue. This lessens the heart’s output to protect itself well before oxygen levels get dangerously low. So the best way to get faster and delay fatigue is to train your brain in addition to your legs and lungs.

The best way to do that, Noakes says, is through working on form and efficiency. For example, he recommends runners evaluate foot contact time, stride length and stride frequency during fast sessions. “The key in fast running is to have a very long stride length from a very short ground contact time,” he says. In swimming, you might focus on increasing distance per stroke and catch efficiency. VO₂ max, Noakes says, just isn’t a very useful stat.

Surprisingly, Noakes’ CGM doesn’t have many critics, in part because it’s difficult to disprove. One review in the British Journal of Physiology argues the CGM is flawed because it can’t explain all forms of exercise, specifically short bursts of explosive power. (Noakes admits that short intervals may have structural limiters—hamstrings for instance.) But there’s very little recent scientific research arguing in favor of VO₂ max’s importance. In fact, it’s nearly impossible to find any studies that oppose Noakes’ idea that VO₂ max indicates anything more than who is best at a VO₂ max test.

The takeaway: Efficiency is key. Focus on form and you should be able to go faster, longer.