Zone 2 Cardio: The Overlooked Key to Fat Burning and Endurance

Everyone talks about HIIT. Nobody talks about Zone 2. Yet professional endurance athletes spend 80% of their training time in Zone 2—not going hard, but going easy.

I used to think easy cardio was a waste of time. "Go hard or go home," right? Then I learned about Zone 2 training and why the fittest people in the world do most of their cardio at low intensity.

What Is Zone 2?

Heart rate training divides intensity into zones:

• Zone 1: Very easy, barely above rest
• Zone 2: Easy, sustainable for hours
• Zone 3: Moderate, getting harder
• Zone 4: Hard, can maintain 20-40 minutes
• Zone 5: Maximum effort, can only sustain briefly

Zone 2 is approximately 60-70% of your maximum heart rate. For most people, this is 120-150 beats per minute.

The key marker: you can hold a conversation. If you're breathing too hard to talk comfortably, you're above Zone 2.

Why Zone 2 Matters

Metabolic Efficiency

Zone 2 is where your body primarily burns fat for fuel. At higher intensities, you switch to using more carbohydrates.

Zone 2 training improves:

• Mitochondrial density (more cellular powerhouses)
• Fat oxidation capacity (ability to burn fat)
• Metabolic flexibility (switching between fuel sources)
• Aerobic base (foundation for all other training)

Sustainable Volume

You can do a lot of Zone 2 without burning out:

• Doesn't require significant recovery
• Can be done daily
• Doesn't impair strength training
• Low injury risk

Professional athletes do 80% easy / 20% hard for a reason—it allows more total training volume without overtraining.

Health Benefits

Research links Zone 2 training to:

• Improved cardiovascular health
• Better blood sugar regulation
• Reduced inflammation
• Potential longevity benefits

Dr. Peter Attia and other longevity researchers specifically recommend Zone 2 cardio as a health practice.

How to Calculate Your Zone 2

Simple method (estimated max heart rate):

• Max HR = 220 - your age
• Zone 2 = 60-70% of max

Example for a 30-year-old:

• Max HR = 220 - 30 = 190
• Zone 2 = 114-133 BPM

Talk test method:
Can you hold a conversation without gasping? If yes, you're in Zone 2. If you're struggling to speak in full sentences, slow down.

MAF method (Maffetone):

• Zone 2 HR = 180 - your age
• Adjust down for health issues, up if very fit

Example for a 30-year-old: 180 - 30 = 150 BPM ceiling

Why Most People Train Too Hard

Problem: Most recreational exercisers spend almost all their time in Zone 3—too hard for aerobic development, too easy for anaerobic benefits.

This "moderate" intensity feels productive but provides the worst of both worlds:

• Too hard to accumulate volume without fatigue
• Not hard enough to trigger high-intensity adaptations

The solution: Polarize your training. Either go truly easy (Zone 2) or truly hard (Zone 4-5). Minimize time in the "gray zone."

Zone 2 Activities

Any sustained activity can be Zone 2:

• Walking (brisk pace, possibly with incline)
• Cycling (most accessible Zone 2 activity)
• Rowing (if you can maintain the pace)
• Swimming (great low-impact option)
• Elliptical (easy to control intensity)
• Light jogging (many need to walk to stay in Zone 2)

Note: For many people, running automatically pushes them above Zone 2. Walking with an incline or cycling are often easier for maintaining Zone 2.

How Much Zone 2?

Minimum effective dose: 3 hours per week for health benefits

Optimal for fitness: 4-7+ hours per week

For most people: Start with 30-45 minutes 3-4x per week. Build from there.

This sounds like a lot, but remember—it's easy effort. You can:

• Walk during phone calls
• Bike while watching TV
• Use a treadmill desk
• Break it into shorter sessions

Zone 2 for Lifters

If your primary focus is strength training, Zone 2 is the best cardio choice:

Benefits:

• Improves recovery between sets
• Enhances work capacity
• Doesn't impair muscle building
• Minimal recovery demands

Practical approach:

• 3-4 sessions of 30-45 minutes weekly
• On rest days or after lifting
• Walking or cycling (low impact)

This is enough for health benefits without compromising strength goals.

Common Mistakes

Going too fast:
If it feels like "real" cardio, you're probably too fast. Zone 2 should feel easy—almost too easy at first.

Not tracking heart rate:
Without a monitor, most people overestimate their effort. A basic HR monitor helps keep you honest.

Expecting immediate results:
Zone 2 benefits build slowly over months. It's playing the long game.

Skipping it for "harder" workouts:
HIIT feels more productive in the moment, but Zone 2 builds the aerobic foundation that makes everything else better.

My Zone 2 Practice

• 4 sessions per week of 30-45 minutes
• Usually walking with incline or stationary bike
• Heart rate monitor to stay in zone
• During podcasts, audiobooks, or Netflix

It's my recovery cardio, my fat-burning cardio, and my health investment—all in one.

The Bottom Line

Zone 2 cardio is the most underrated training method. It builds aerobic base, improves fat-burning capacity, enhances recovery, and provides significant health benefits—all without interfering with other training. Keep your heart rate at 60-70% of max (conversational pace), aim for 3+ hours per week, and be patient as the benefits accumulate over months.