The hype about Zone 2?
Zone 2 training has become the latest hot topic in fitness and longevity and for good reason. I have personally found that my endurance base has improved the most since I found my Zone 2 heart rate and incorporated it into my weekly training.
What Is Zone 2
Zone 2 is the sweet spot where your body is using predominately fat as an energy source over glycogen. Exercising in zone 2 increase the number and efficiency of the mitochondria. This is important because mitochondria convert glucose and fat into ATP (energy for working out) ref. Higher quality mitochondria have a greater capacity for fat oxidation. Poor performing Mitochondria can lead to conditions including, skeletal muscle atrophy, diabetes and cardiovascular diseases ref. If you are untrained you will find that your body moves straight to burning glucose for energy much earlier than if you are well training ref.
How To Determine Your Zone 2
Lactic Acid Testing
Lactic acid testing is the gold standard for determining your zone 2, however, it is also the most expensive. The top end of your zone 2 is determined when you blood lactate rises above 2 mmol/L. The best ways to measure this is through a handheld monitor (but they are expensive), or by combining lactic acid testing with your VO2 max test.
VO2 Max Test
Using the data gathered from a VO2 max test is the next most accurate way to determine your heart rate zones. During the test you will either cycle or run, while a mask covering your nose and mouth monitors the oxygen you breathe in and the CO2 you expel. The test will ramp up every 2 minutes or so, increasing power for cycling or pace for running, up until you can’t push anymore. During the course of the test your heart rate is also measured and is lined up with the changes to the gas exchange within your lungs.
From all this data the test can determine at which heart rate, power or pace your body transitions from a steady zone 2 state, to a more intense zone 3.
Online Heart Rate Calculators
There are a lot of heart rate zone calculators online and they all work using the same inputs. If you know your max and resting heart rates this is best, but if not, they will just use 220 minus your age as the max and 60 as your resting. While these work as a more general estimate you can find that they can vary drastically compared to the methods above.
How My Actual Zone 2 Compares To Online Calculators
In mid 2023 I decided to take a VO2 max test for 2 main reasons, firstly to get a baseline of my VO2 max so I had a target to improve from and secondly, to determine my heart rate training zones. Unlike the online calculators that estimates your HR zones a VO2 max test measures the gas exchange within your lungs while also tracking heart rate. From the data it can be determined at what exact heart rate your body switches from a steady state level, to a more linear increase.
I compared this range to a few different calculators I found online using my own max and resting heart rates and as you can see the differences are quite dramatic.
Training In Zone 2
After using an accurate way to determine your zone 2 you will likely find that the equivalent running pace or cycling speed is actually a lot slower than you expected. I personally found that I had to alternate between running and walking at first to keep my heart rate within the zone. Hiding the pace or speed from my workout computers helped a lot while I took the time to build my base fitness.
Now I am able to maintain a constant running pace or cycling speed for extended durations with minimal recovery time required between workouts.