How Zone 2 Training Impacts VO2 Max—and Why It’s Essential for Endurance (Part 2 of 3)
Part 2 of The Zone 2 Blueprint series
In Part 1 of this conversation about Zone 2 Training, we explored how total weekly Zone 2 training volume may have more impact than the duration of any single session. But if Zone 2 is so low-intensity, you might be wondering:
“Does Zone 2 training actually improve VO2 max?”
The answer? Yes but not in the way most people think.
Zone 2 training indirectly improves VO2 max by strengthening your body’s ability to use oxygen efficiently. It lays the foundation for endurance performance, but if you want to maximize VO2 max, you’ll need to include some high-intensity work, too.
Let’s break it down.
First, What Is VO2 Max and Why Should You Care?
VO2 max is the maximum amount of oxygen your body can use during exercise. Think of it as your engine size—the bigger the engine, the more power you can generate.
Higher VO2 max = Better cardiovascular fitness.
But why does VO2 Max matter?
✅ Predicts Endurance Performance – Higher VO2 max means you can sustain faster paces with less effort.
✅ Increases Work Capacity – The higher your VO2 max, the longer you can train at high intensities.
✅ Improves Heart Health – VO2 max is linked to longevity and overall cardiovascular health.
Fun Fact: The highest recorded VO2 max belongs to Norwegian cyclist Oskar Svendsen (97.5 ml/kg/min) almost twice that of an average person!
How Zone 2 Training Improves VO2 Max
Most people associate VO2 max training with high-intensity intervals (HIIT). While HIIT is effective, Zone 2 plays a crucial role in setting up your body for higher VO2 max gains.
Here’s how consistent Zone 2 training improves VO2 max over time:
✅ 1. Strengthens Your Heart (Increases Stroke Volume)
Zone 2 enlarges the left ventricle of the heart, allowing it to pump more blood per beat.
More blood pumped = more oxygen delivered to muscles at all effort levels.
✅ 2. Increases Mitochondrial Density & Efficiency
Mitochondria are your body’s energy factories more mitochondria = better oxygen utilization.
Zone 2 teaches your body to rely on fat for fuel, delaying fatigue and boosting endurance.
✅ 3. Enhances Capillary Density (Better Oxygen Delivery)
More capillaries = better blood flow to muscles, which means more oxygen is available during hard efforts.
✅ 4. Raises Aerobic Threshold (Delays Fatigue at Higher Intensities)
A higher aerobic threshold means you can stay in the “aerobic zone” longer before switching to anaerobic metabolism.
This allows you to train harder before accumulating lactic acid and fatigue.
Why Zone 2 Alone Won’t Maximize VO2 Max
While Zone 2 builds the foundation for endurance, it won’t push your cardiovascular system to its max. To fully develop VO2 max, you need to include some higher-intensity training.
Here’s why:
VO2 max training requires working at 90–100% of your max heart rate.
Your body needs to be pushed to its limits to stimulate VO2 max increases.
Without intensity, you’re improving efficiency, not pushing capacity.
That’s why elite endurance athletes do both:
Zone 2 for aerobic efficiency (bulk of training)
VO2 max intervals to raise ceiling (1–2 sessions per week)
How to Combine Zone 2 and VO2 Max Training for Maximum Gains
To get the best of both worlds, follow this simple structure:
✅ Step 1: Build Your Base (4–6 weeks of Zone 2 Focus)
Focus on 4–6 hours per week of Zone 2 training to improve mitochondrial and cardiovascular efficiency.
✅ Step 2: Introduce VO2 Max Workouts (Weeks 7–12)
Keep 3–4 Zone 2 sessions per week to maintain your aerobic base.
Add 1–2 high-intensity sessions per week to push VO2 max higher.
Best VO2 Max Workouts
4x4 Intervals – 4 rounds of 4 min at 90–95% max HR, with 4 min recovery.
5x3 Intervals – 5 rounds of 3 min hard, 3 min easy recovery.
30/30 Fartlek – 30 sec sprint, 30 sec easy, repeat 12–15 times.
Pro Tip: Avoid doing VO2 max sessions on back-to-back days your body needs time to recover.
The Takeaway: Zone 2 + Intensity = VO2 Max Gains
Here’s what we know:
✅ Zone 2 training improves VO2 max indirectly by strengthening the heart, increasing capillary density, and boosting mitochondrial efficiency.
✅ High-intensity intervals directly increase VO2 max by pushing your cardiovascular system to its max.
✅ The best approach is a mix of both a solid Zone 2 base with 1–2 intense VO2 max workouts per week.
Coming Up in Part 3:
Now that we’ve covered how Zone 2 affects VO2 max, we’ll wrap up this series with Part 3, where we’ll discuss:
🔹 How to structure a long-term training plan (balancing Zone 2 and intensity)
🔹 Common mistakes people make when training for endurance
🔹 How to measure progress beyond VO2 max
Stay tuned!
Cant wait for part 3? Take out the guesswork and get started with my 12 Week Zone 2 VO2 Max Training program.
Sources & Further Reading
📚 Seiler, S. (2010). Best practices for training intensity and duration distribution in endurance athletes. International Journal of Sports Physiology & Performance.
📚 Murias, J. M., Kowalchuk, J. M., & Paterson, D. H. (2018). Mechanisms for increases in VO2 max with endurance training. Sports Medicine.
📚 Maffetone, P. (2014). The Big Book of Endurance Training and Racing.