Zone 2 Cardio

I wrote a blog post about Zone 2 cardio a few years ago. It was one of my most popular and requested blog posts. People still PM me looking for a link to it. Once again, popular media has done a poor job of educating people on what it is and how to do it. Hint: It isn’t that 60% to 70% on your Heart rate tracker.

Zone 2 cardio is having a moment, and for good reason. It’s one of the most effective tools for improving heart health, building endurance, and increasing fat metabolism.

If you've ever jumped on a treadmill, half-jogged while watching a podcast, and told yourself it was Zone 2, chances are, it wasn’t.

Let’s fix that.

What Is Zone 2?

Zone 2 is a low-intensity heart rate zone, the sweet spot where your body primarily burns fat for fuel and builds aerobic endurance. It's where you can still talk, breathe through your nose, and feel like you could go for a long time.

The Talk Test: You should be able to carry on a conversation, but singing would be too hard.

Done right, it improves:

• Mitochondrial health (your body’s energy system)
• Cardiovascular function
• Metabolic flexibility (how well your body burns fat vs. carbs)

How People Get It Wrong

1. Too intense
Going too fast bumps you into Zone 3, where you’re no longer building that aerobic base.

2. Too short
Ten minutes isn’t enough. You need at least 30 to 60 minutes to get the benefits.

3. No tracking
Without a heart rate monitor or awareness of effort, you’re just guessing.

4. No progression
Like strength training, Zone 2 needs to be progressed over time to see improvements.

How to Find Your True Zone 2 Heart Rate

Zone 2 is not a one-size-fits-all number. It’s a physiological range, not just a guess based on age. Here are the best methods, from simplest to most scientific:

Maffetone Formula (Simple and Popular)
Use the formula:
180 minus your age = max aerobic heart rate
This gives you the upper limit of Zone 2.
Adjustments:
-5 bpm if you're recovering, new to training, or chronically stressed
+5 bpm if you're highly trained and injury-free
Example: A 40-year-old would target around 140 bpm

Heart Rate Reserve (More Personalized)
Step 1: Measure your resting heart rate (RHR)
Step 2: Estimate your max heart rate (MHR), either from testing or using 220 - age
Step 3: Calculate heart rate reserve (HRR):
HRR = MHR - RHR
Then find Zone 2 as:
(HRR × 0.60 to 0.70) + RHR = Zone 2 range
Example:
RHR = 60
MHR = 180
HRR = 120
Zone 2 = 132 to 144 bpm

Lactate Testing (Gold Standard)
In a lab, Zone 2 corresponds to a lactate level of ~2 mmol/L.
This is the most accurate way to pinpoint your aerobic threshold, but it requires equipment and cost.

Respiratory Exchange Ratio (RER) Testing
During a VO₂ max test, Zone 2 is when your RER is ~0.85, meaning you're burning roughly equal parts fat and carbs.
Typically occurs at about 60 to 70% of your VO₂ max. (Note: This is not the same as HR)

The Talk Test (Surprisingly Reliable)
If you can talk in complete sentences but not sing, you're likely in Zone 2.
You’re breathing a little heavy, but steady.

Pro Tip: Use a heart rate monitor to get objective feedback and track your pace or power over time. As fitness improves, you’ll go faster or farther at the same Zone 2 heart rate — a clear sign of aerobic progress.

What Affects Your Zone 2 Day-to-Day?

Your Zone 2 heart rate range isn’t carved in stone. It can shift depending on:

• Sleep and recovery
• Stress and nervous system load
• Caffeine or stimulants
• Dehydration or poor nutrition
• Heat, humidity, or altitude
• Sickness or overtraining

Some days, a brisk walk will get you there. Other days, you may need to slow your pace even more to stay within the right range. That’s normal — Zone 2 is about internal response, not external speed.

What a Good Zone 2 Week Looks Like

Here’s a simple weekly plan for gym-goers or anyone focused on long-term health:

• Two to four sessions per week
• Thirty to sixty minutes each
• Use any modality: treadmill, bike, incline walk, rower, ruck

Bonus tip: Stack it on rest days, or after lifting sessions, to improve recovery and build capacity without added strain.

Why You Should Care

If you're lifting weights and skipping cardio, Zone 2 gives you:

• A bigger engine for your workouts
• A stronger, more resilient heart
• More energy throughout your day
• A better ability to burn fat efficiently

Think of it as the aerobic base that supports everything else — strength, endurance, recovery, and longevity.

Final Word

Zone 2 is the most potent “easy” workout you’re probably not doing right.

It doesn’t leave you drenched in sweat. It doesn’t destroy your legs. But it does build the kind of lasting fitness foundation that pays dividends for years.

Slow it down. Track it properly. Stay consistent.

See you in the gym!

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