Zone 2 Training Demystified

Written by Jon Bula: Masters Athlete, Cat 2 Cyclist, MSc in Exercise Physiology

Many of us have heard about Zone 2 training, or aerobic base training. The challenge lies in understanding how to use it effectively and determining the actual intensity required to be in Zone 2. I’m going try and really simplify things for you in this post and I’ll provide some great links if you would like to dive deeper.

What is Zone 2?

It is an exercise intensity that elicits a heart rate around 70% of your maximum heart
There is large variability in maximum heart rate, so without proper physiological testing it is very difficult to to say exactly where your Zone 2 sits
The best method to determine it without proper physiological testing is to use the talk test while exercising
- Imagine you are doing an indoor bike ride while participating in a 60-minute phone meeting. While in Zone 2 you should be able to carry on a conversation for the entire meeting, but the person on the other end of the line should be able to tell that you are exercising. If someone can’t tell you are exercising from hearing your breathing then you are likely in Zone 1, if you can’t participate in the conversation without gasping you are above Zone 2. It’s actually that simple.
The tendency for most people is to work too hard while attempting a zone 2 workout
Zone 2 is range: as an example here are my numbers as determined through laboratory testing:
- Max HR 186
- Zone 2 HR range: 132 – 148, or 70-79% of my max HR – note, I’ve trained several years to improve Zone 2 as such my top end of that range is a bit higher than average

Why do Zone 2?

If you want to be fast at the end of a race, do more Zone 2
If you want to recover from a hard effort faster, do more Zone 2
If you want to live a longer and healthier life, do more Zone 2
If you want to greatly reduce your chances of heart disease, insulin resistance, type 2 diabetes, cancer, chronic inflammation, among others, do more Zone 2

How does Zone 2 do all of that?

I’m not going to go too deep into the physiological processes behind all of this, I’ll leave that to you to investigate further the links I’ve suggested. These are the take home points:

Mitochondria (think of these as the powerhouse or engine room of our cells) are susceptible to training as well as inactivity.
Zone 2 training is the intensity that triggers improvements in Mitochondrial health and function – training above this intensity does not (intense training improves other things and is definitely important/beneficial)
Improved mitochondrial health is highly correlated to longer healthier lives
Zone 2 training:
- Increases the number of mitochondria – more is better
- Increases the flexibility of mitochondria: poor mitochondrial flexibility leads to a poor ability to use fat as a fuel and increases reliance on glucose – this can make us want to eat more and crave sugars
- Increases efficiency of mitochondria: better able to use fat and lactate as a fuel
When you have good mitochondrial health you fortify your body against most chronic diseases. It really is one of the key ways to live healthier for longer.
When you have poor mitochondrial health (this can occur alarmingly quickly from inactivity or even by only training at high intensities) you can quickly become insulin resistant and this can cascade into many other health issues over time.

How much Zone 2?

Endurance athletes should spend roughly 70% of their training time in Zone 2 (more if training volumes are high)
To lead a healthier lifestyle accumulating 3-4 hours of exercise per week at this intensity is key
It would appear that you can’t really do too much Zone 2. Unlike high intensity training, Zone 2 work doesn’t have the same impact on the body and doesn’t require the same amount of recovery
Zone 2 is just one aspect of training, but it is a crucial part that is often overlooked or done improperly (intensity too high)

Train for a better life: train more in Zone 2!

Links:

https://www.howardluksmd.com/zone-2-hr-training-live-longer-less-injury/

https://peterattiamd.com/live-qa-on-zone-2-exercise/

https://podcasts.apple.com/ca/podcast/the-peter-attia-drive/id1400828889?i=1000661504448

https://peterattiamd.com/how-to-find-your-zone-2-without-using-a-lactate-meter/