What is zone 2 running?
The easy end of aerobic training. Useful, genuinely evidence-backed, and more confusing than it needs to be.
Where the idea actually comes from
The research underneath zone 2 is about how elite endurance athletes distribute their training, not about a magic zone.
Across rowing, skiing, running and cycling, athletes training ten to thirteen times a week were found to put roughly 80 percent of their sessions at low intensity and about 20 percent at genuinely hard intensity, with little in between. Studies pushing more of the volume into the hard middle did not produce convincing long-term gains. [1]
That is a real and useful finding. Most people who take up running do the opposite: everything at a moderate, uncomfortable, unsustainable middle pace.
The catch nobody mentions: zone 2 does not mean one thing
The research above uses a three-zone model, where zone 1 is the easy work below the first lactate threshold and zone 2 is the awkward middle that athletes mostly avoid. [1]
The five-zone model on your watch numbers things differently, and there zone 2 is the easy one.
So when someone says to do more zone 2, they almost certainly mean the easy end. But in the model the underlying research uses, zone 2 is the exact thing that research says to spend less time in. Same two words, opposite instruction. If a zone chart ever seems to contradict an article, this is usually why.
What matters more than the label
The boundary worth knowing is the point where easy stops being easy. Physiologically that is your first lactate threshold. Practically, it is where you stop being able to speak in full sentences.
You do not need a lab, and you do not need a formula, which is fortunate given that age-based heart rate formulas predict a population average rather than your own maximum. [2]
If you have not run in years, most of this is moot
The 80/20 research is about people training ten to thirteen times a week. That is not the situation you are in.
From a standing start, almost any running is above your easy zone. That is not a flaw in you, it is what an untrained aerobic system does. The tool that gets you an easy zone at all is walking, and then walking with a little running in it.
Which is the part worth taking from all of this: not the number, the principle. Nearly all of your work should be easy enough to sustain and talk through. Beginners who ignore that are injured at more than twice the rate of experienced runners. [3]
Common questions
How do I know if I am in zone 2?
Try to say a full sentence out loud. If it comes out whole, you are in the easy range. If you are breaking it into three or four word pieces, you are above it. This works without a watch and adjusts itself on a hot day.
Why is zone 2 numbered differently in different places?
Because there are competing models. The three-zone model used in the training-distribution research calls the easy work zone 1, while the five-zone model on most watches calls it zone 2. The words collide and the meanings do not.
Can I do zone 2 by walking?
Yes, and if you are starting from sedentary that may be the only way you can reach it at all. Brisk walking, especially uphill, sits squarely in the easy aerobic range for most untrained adults.
References
- Seiler S. What is Best Practice for Training Intensity and Duration Distribution in Endurance Athletes?. International Journal of Sports Physiology and Performance 5(3):276-291, 2010.
- Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. Journal of the American College of Cardiology 37(1):153-156, 2001.
- Videbaek S, Bueno AM, Nielsen RO, Rasmussen S. Incidence of Running-Related Injuries Per 1000 h of running in Different Types of Runners: A Systematic Review and Meta-Analysis. Sports Medicine 45(7):1017-1026, 2015.