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How to Calculate Your Aerobic Threshold

Learn how to calculate your AeT using these simple techniques

Zone 1, Lactate Threshold, Aerobic Threshold – are you overwhelmed yet? We get it! In the modern era of endurance performance, there is more jargon than hours in a week – and it’s not helping us get any fitter! What we need is to boil it down to a few critical markers that all endurance athletes can use to improve their performance. None are more important than our Aerobic Threshold (AeT). In this post, we cover why this is so important and share easy ways you can calculate your aerobic threshold.

What is the Aerobic Threshold?

The AeT is your happy place, your steady state, the effort level below which you can go all day. In scientific terms this happy place correlates with blood lactate levels below 2Mmol/L. As you increase your effort above this level, blood lactate will continue to climb steeply, and will soon lead to an unsustainable cellular environment – causing us to slow down or stop entirely.

calculate aerobic threshold
Photo: Mark Fisher

Why is Aerobic Threshold Important?

Your threshold is a metabolic ‘line in the sand’ – when you cross it, a cascade of changes occur that dramatically decrease your efficiency, and expedite the need to rest and recover. Your ability to perform below your AeT is quite literally the #1 measure of endurance performance.

Training can shift your AeT, making you capable of covering the same ground with less energy and lower perceived effort. Beyond the stats, and the performance metrics, life in the mountains feels awesome below our AeT – you have almost endless energy because your body is burning fat, your mind can wonder and you feel fantastic.

How Do I Calculate My Aerobic Threshold?

I preface my answer with this: there are few characteristics more innately human than our aerobic engine. No animal in the history of the planet has an aerobic engine to match the one you were born with.

The reason I say that is to head off ideas of needing HR monitors, wearable devices or other external ways to measure your AeT. Don’t get me wrong – those things are all fine and can be helpful. But there is one measurement device hardwired into the human body – the brain. You were born with the most accurate way of calculating your aerobic threshold. You just have to know how to interpret it.

Without Using a Heart Rate Monitor

Gauging your aerobic threshold without a device is easy and simple. Start by walking on flat ground and gradually increase your pace over 10mins. As you do so, notice the sensations that accompany your increasing level of effort. 

Here are 3 signs that you are operating BELOW your Aerobic Threshold:

  1. You can comfortably breathe through your nose. This doesn’t work for everyone. Many athletes unaccustomed to nasal breathing find it hard and uncomfortable – it takes some practice. Nevertheless, as you get used to it, it can become a very helpful marker of effort.
  2. You can speak in paragraphs. While running and talking isn’t easy for anyone, when you operate below your AeT you’re able to speak in full sentences and string sentences together without needing to gasp or take a break.
  3. Your mind is free to wander. This may seem vague or unscientific, and it is – but over 20 years of aerobic training, I have come to trust this marker more than any other. When my mind is wandering, I’m daydreaming, and that’s as sure a sign as I know that I’m below my AeT. As soon as the sensations of my body and the discomfort of the work bring me back to the present moment, I know I’ve crossed the line.
aerobic threshold calculator
Photo: Fred Marmsater

Using the MAF Method

The Maximum Aerobic Function Method developed by Phil Maffetone is a remarkably accurate predictor of your baseline AeT. To calculate your AeT using the MAF Method, simply subtract your age from 180. This tends to yield accurate measures for the lightly trained, but elite endurance athletes will outperform their MAF.

Using a Heart Rate Monitor

The only difference in calculating your AeT with a HR monitor is that it allows you to pinpoint the heart rate at which these changes occur. That can be a worthwhile exercise for monitoring improvements in your Aerobic Capacity over a period of time.

While there are many more data-centric ways of measuring AeT – these simple analog tests will not only give you an accurate measure of your AeT, they will teach you to better interpret your own physiology, which is a key to performing as an athlete.

Bottom Line

In the most practical terms, what we are ultimately trying to determine is the fastest pace at which you can go all day. The answer to that question is about more than just Mmol/L measurements, it’s also about metabolic rates and fat versus carbohydrate fueling.

While that is all beyond the scope of this post, we have to remember there is only one supercomputer wired into the engine of our body. That computer is the one we were all born with – the brain. As athletes, we must learn to become better interpreters of our own physiology; to read the signs and interpret the sensations. Trusting our brains to do that for us is part of the journey of becoming better athletes.


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