If you’ve ever trained for a half marathon or marathon, there’s a good chance you’ve heard someone say: “Make sure you spend plenty of time in Zone 2.” Maybe you nodded, maybe you even slowed your pace a bit, but deep down you weren’t totally sure what Zone 2 actually meant. Is it just “easy running”? Is it jogging? And how slow is too slow?
Many recreational runners get confused here. They either run too hard on easy days or think Zone 2 is just “junk miles.” The truth is, Zone 2 is one of the most powerful tools you can use to build endurance for longer races.
QUICK TAKEAWAYS
Zone 2 is a comfortably easy effort where you can speak in full sentences.
Zone 2 running increases the number and efficiency of mitochondria in your muscle cells, which are the powerhouses that generate energy.
You can estimate Zone 2 using heart rate (~60–70% of Heart Rate Reserve), the talk test, or by anchoring it to a pace that feels easy and sustainable for at least an hour.
Zone 2 sits below your first lactate threshold (LT1) and isn't a fixed pace--it changes with heat, hills, fatigue, and fitness.
A common recommendation for endurance athletes is to spend about 80% of their total training time in Zone 2.
The Karvonen method (using Heart Rate Reserve) is a practical way to personalize your Zone 2 heart rate range.
What Exactly is Zone 2 Running?
At its simplest, Zone 2 running is “easy running” -- but not too easy. It’s the effort where you could comfortably hold a conversation in full sentences, but you probably couldn’t sing.
Most training systems divide heart rate into 5 zones. Zone 2 is the second one from the bottom, usually sitting around 60–70% of your Heart Rate Reserve (HRR). It feels easy at first, but it’s not a slow shuffle. After 45–90 minutes, you’ll notice the steady effort building.
Think of Zone 2 as the engine room of your endurance. It’s not glamorous, but it’s what allows you to run strong in the later miles of a race.
Why Zone 2 Matters for Endurance and Fat Metabolism
Your body primarily uses fat as a fuel source, sparing glycogen (carbohydrate stored in muscles).
You build more mitochondria, the tiny “power plants” inside your cells that produce energy.
Your cardiovascular system adapts—your heart pumps more efficiently, and your blood delivers oxygen better.
These adaptations mean you can run longer before fatigue sets in. For marathoners, this is gold: it delays “the wall” by teaching your body to rely less on limited glycogen stores.
Without a strong Zone 2 base, all the speed work in the world won’t save you from fading in the second half of a long race.
How to Measure Zone 2
a. Heart Rate
Use the Karvonen formula (explained later) or your watch’s zone settings. For most runners, Zone 2 is about 60–70% HRR or roughly 65–75% of max heart rate.
b. Talk Test
If you can talk in full sentences without gasping → you’re in Zone 2.
If you can only say a few words → you’ve drifted into Zone 3 or higher.
If you can sing → you’re probably in Zone 1.
c. Pace
Zone 2 pace is typically 90–120 seconds per mile slower than your 10K race pace. Example: If you run a 10K at 8:00 per mile, your Zone 2 pace might be 9:30–10:00 per mile.
Key Physiological Terms You Should Know
Heart Rate Reserve (HRR)
HRR = Max Heart Rate – Resting Heart Rate.
Example: If your max HR is 200 bpm and resting HR is 50 bpm, your HRR = 150.
Training zones are then calculated as percentages of HRR added back to your resting HR.
This method (the Karvonen method) is more precise than using max HR alone, because it accounts for individual fitness differences.
Lactate Threshold 1 (LT1)
The intensity where blood lactate first starts to rise above resting levels.
LT1 ≈ top of Zone 2. Staying below LT1 means you’re still solidly aerobic.
Lactate Threshold 2 (LT2)
The intensity where lactate accumulates faster than your body can clear it—essentially your “red line.”
LT2 ≈ top of Zone 4. Training here is hard and can’t last long.
The Karvonen Method
Target HR = Resting HR + (HRR × % intensity)
Example:
Resting HR = 50
Max HR = 200 → HRR = 150
Zone 2 (60–70%):
50 + (150 × 0.6) = 140 bpm
50 + (150 × 0.7) = 155 bpm
So Zone 2 = 140–155 bpm.
Illustration: Heart rate zones (example ranges as % of max HR).
Common Myths and Mistakes
Myth 1: Zone 2 is just jogging
Not quite. True Zone 2 is steady and purposeful. Jogging too slowly (Zone 1) won’t provide the same aerobic stimulus.
Myth 2: Faster is always better
Running most of your weekly mileage too fast (Zone 3) leaves you tired, but without the aerobic benefits of Zone 2 or the high intensity gains of Zone 4. It’s “no man’s land.”
Myth 3: Elite runners don’t bother with Zone 2
In fact, elites often spend 70–80% of their training in Zone 2. Their easy runs might still look fast, but relative to their fitness, they’re staying aerobic.
Myth 4: You’ll lose speed if you run slow
Zone 2 doesn’t make you slower—it supports your ability to run faster for longer. Speed work adds sharpness, but Zone 2 builds the base.
How to Incorporate Zone 2 into Your Training
Weekly Mileage
Aim for 60–80% of your total mileage in Zone 2.
Example: If you run 40 miles per week, 25–30 of those should be Zone 2.
Long Runs
Classic Zone 2 sessions. Run steadily for 90–120 minutes at conversational pace.
This is where you build the endurance engine.
Recovery Runs
Easy days should stay in Zone 2 (or even Zone 1 if you’re tired).
This keeps blood flowing without stressing your system.
Mix with Speed Work
Add 1–2 quality sessions per week (intervals, tempo, hills).
The rest should be Zone 2. This balance lets you adapt without burning out.
Practical Example (Half Marathon Training, 5 days/week)
Mon: Rest or cross train
Tue: Intervals (Zone 4)
Wed: 5–6 miles Zone 2
Thu: Tempo run (Zone 3–4)
Fri: Rest
Sat: Long run 10–14 miles Zone 2
Sun: 4–5 miles Zone 2 recovery
Conclusion: The Power of Slowing Down
Zone 2 running might feel too easy at first—like you’re holding back. But that’s exactly the point. By training your aerobic system, you’re laying the foundation for faster, stronger, and longer running.
So next time you head out, try the talk test. If you can chat but not sing, you’re in the sweet spot. Stick with it consistently, and you’ll notice something magical: your “easy pace” will gradually get faster, without extra effort.
Zone 2 is not wasted time—it’s the hidden key to endurance success.
Recommended Further Reading
International Journal of Sports Physiology and Performance
Brian Chan
Last updated 02 September 2025
