Everything You Need to Know About Zone 2 Training
Unless you’ve been living under a rock for the last few years (and honestly, that’s not the worst idea), you’ve probably heard endurance athletes, coaches, or — most aggressively — podcasters go on and on about zone 2 training.
Elite endurance athletes spend a shocking amount of time going slow. Runners jog. Cyclists pedal easily for hours. All in service of the now-famous mantra: “train slow to race fast.”
That easy effort has been labeled zone 2.
And while the idea is solid, the execution is where things can get messy.
The problem is that no one can quite agree on what zone 2 actually is, how to measure it, or how much of it you really need. Cue endless social media debates and confused recreational athletes wondering if they’re doing it “wrong.”
So… What Is Zone 2?
In a classic 5-zone model, zone 2 is the highest intensity you can sustain while staying predominantly aerobic (meaning your muscles are still primarily using oxygen to produce energy).
Physiologically, it sits just below your first lactate or ventilatory threshold — the point where breathing and lactate start to rise more sharply.
Translated into human terms:
Your breathing is steady and controlled
You can hold a conversation without gasping
Your heart rate is elevated but stable
You’re working on purpose — not strolling, not grinding
If it helps, zone 2 generally lines up with:
~67–82% of max heart rate
Low, steady lactate levels
A perceived effort that feels “comfortably challenging”
If you’re completely bored, you’re probably too easy. If you can’t talk in full sentences, you’re probably too hard.
That’s zone 2.
Why Zone 2 Works (And What It Doesn’t Do)
Zone 2 gets a lot of hype — some deserved, some overstated. It’s not magic, and it’s not the only way to get fit. But it is excellent at building the aerobic foundation that everything else sits on. Here’s what it actually improves:
1. Better Mitochondria (Your Energy Factories)
Zone 2 encourages your muscles to build more — and better-functioning — mitochondria. That means improved energy production, better endurance, and less reliance on limited glycogen stores. You become more efficient.
2. Improved Blood Supply to Muscles
Consistent low-intensity work increases capillary density, allowing oxygen and nutrients to get to working muscles more easily and waste products to clear more efficiently. Translation: better endurance and faster recovery.
3. Improved Fat Utilization
Training just below your first threshold teaches your body to rely more on fat for fuel. Since fat stores are basically endless compared to carbs, this helps delay fatigue and reduces the risk of “bonking.”
4. A Higher “Easy” Ceiling
Zone 2 improves your ability to clear and recycle lactate, which means over time you can run faster or ride harder before things start to feel uncomfortable. Your easy pace gets faster — without feeling harder.
5. Cardiovascular Efficiency
Long, steady aerobic work increases stroke volume (how much blood your heart pumps per beat). Over time, your heart can do more work with fewer beats. Lower heart rate, same output. Win.
6. Mental & Muscular Endurance
Zone 2 builds durability — physically and psychologically. Things that used to feel tiring just… don’t anymore.
How to Actually Train Zone 2 (Without Losing Your Mind)
Here are three practical approaches supported by the research:
1. Long, Steady Sessions
90–120+ minutes
Comfortable, conversational pace
If your heart rate drifts up, slow down
This is the gold standard — but also the hardest to fit into real life. You can break it into chunks if needed.
2. Variable Continuous Training
Mostly zone 2 with short dips into easier zone 1
Example: 10 minutes steady, 2 minutes easy
Great for beginners or those rebuilding endurance
This helps manage fatigue while still accumulating meaningful aerobic work.
3. Mixing Zone 2 With Intensity
Combine zone 2 with higher-intensity intervals
Or tack intervals onto the front or back of an easy session
This is time-efficient and realistic — and yes, it works.
My Honest Take…
Elite endurance athletes spend ~80% of their training at low intensity because it works for them. That doesn’t mean you need to micromanage your heart rate zones to get fitter.
Personally? When I’m in maintenance mode, I don’t plan my week around zone percentages. I go easy when it’s easy, hard when it’s hard, and sometimes easier or harder than planned. I’m undoubtedly accumulating plenty of zone 2 without labeling it — and that’s okay. If I’m training for an aerobic event, or working on improving my body composition, my week includes 90-120 minutes of planned zone 2 training.
Measuring can be useful. Obsessing is not.
I’ll leave you with this running haiku from legendary physiologist Dr. Michael Joyner:
Run a lot of miles
Some of them very, very fast
Rest once in a while
Don’t get lost in the nuances.
And please — remember to have fun!
