If you follow longevity experts like Peter Attia, Andrew Huberman, or elite endurance coaches, you've heard about Zone 2 training. This moderate-intensity cardio zone— where you can still hold a conversation but feel like you're working—has become the cornerstone of longevity-focused exercise protocols. But why? And how does it actually affect your biological age?

What is Zone 2 training?

Zone 2 refers to a specific heart rate zone—typically 60-70% of your maximum heart rate. For most people, this feels like a brisk walk, easy jog, or moderate cycling pace. The key characteristic: you can maintain a conversation without gasping, but you're definitely aware you're exercising.

At this intensity, your body primarily burns fat for fuel and relies on aerobic (oxygen- using) metabolism. This is the intensity where you build mitochondrial density and efficiency—the cellular powerhouses that determine metabolic health and aging.

How Zone 2 training lowers biological age

1. Improves VO₂max over time

VO₂max—your body's maximum oxygen uptake—is the single strongest predictor of longevity and a major component of biological age calculations. While high-intensity intervals produce faster VO₂max gains, Zone 2 training builds the aerobic foundation that supports sustainable improvement.

Elite athletes spend 80% of their training time in Zone 2 for this reason. The large volume of easy aerobic work creates adaptations that can't be achieved with intensity alone: more capillaries, larger left ventricle, increased mitochondrial density, and improved fat oxidation.

2. Builds mitochondrial health

Mitochondria are your cellular energy factories, and their function declines with age. Zone 2 training specifically stimulates mitochondrial biogenesis (creation of new mitochondria) and improves the efficiency of existing ones. This metabolic fitness directly impacts how young your cells function.

3. Improves metabolic flexibility

The ability to switch between burning carbs and fat is called metabolic flexibility— and it deteriorates with age and inactivity. Zone 2 training restores this flexibility by training your body to efficiently oxidize fat. Better metabolic flexibility correlates with lower biological age and reduced chronic disease risk.

4. Supports recovery and HRV

Unlike high-intensity training, Zone 2 doesn't create significant stress or recovery debt. You can do it frequently without suppressing HRV or requiring extended recovery. This allows consistent training volume that accumulates adaptations over time.

The optimal Zone 2 protocol for biological age

How much Zone 2?

Longevity experts like Peter Attia recommend 150-200 minutes of Zone 2 per week— ideally spread across 3-4 sessions of 45-60 minutes. This can include walking, cycling, rowing, swimming, or any sustained aerobic activity.

How to find your Zone 2

Heart rate method: 60-70% of max HR (roughly 180 minus your age, minus 10-20 BPM)
Talk test: You can speak in complete sentences but prefer not to
Perceived effort: 4-5 out of 10 difficulty
Nose breathing: You can breathe through your nose the entire time

Sample weekly schedule

Monday: 45-60 min Zone 2 (cycling, walking, or rowing)
Tuesday: Strength training
Wednesday: 45-60 min Zone 2
Thursday: Strength training or rest
Friday: 45-60 min Zone 2
Saturday: 60-90 min Zone 2 (longer session)
Sunday: Active recovery or rest

Track Zone 2 benefits with My Bio Age

Implementing Zone 2 training should improve multiple biological age metrics over 8-12 weeks. Here's what to watch for in My Bio Age:

VO₂max trend — Should gradually increase as aerobic capacity builds
Resting heart rate — Often decreases with improved cardiac efficiency
HRV — May improve as recovery capacity increases
Recovery Capacity — Should trend upward with better aerobic base
MyBioAge Index™ — Overall biological age should decrease

The weekly digest shows which metrics improved and by how much, helping you see the direct impact of your Zone 2 training on biological age.

Common Zone 2 mistakes

Going too hard — The biggest mistake. If you're breathing heavily, you're not in Zone 2.
Not enough volume — Occasional easy sessions don't build adaptations. Consistency matters.
Expecting fast results — Zone 2 benefits accumulate over months, not weeks.
Replacing all intensity — Zone 2 should be the base, but some high-intensity work is still beneficial.

Start your Zone 2 journey

Zone 2 training is the most accessible longevity intervention available. You don't need a gym, expensive equipment, or athletic background. A brisk walk counts. What matters is consistency and accumulation over time.

Download My Bio Age to establish your baseline biological age, then implement a Zone 2 protocol. Track VO₂max, HRV, and your overall MyBioAge Index™ as adaptations build. The data will show you exactly how exercise affects aging—and motivate you to keep going.