Question 1

What is the Karvonen method for heart rate zones?

Accepted Answer

Target HR = ((Max HR − Resting HR) × Intensity%) + Resting HR. The Karvonen method uses heart rate reserve (HRR) for more accurate zones than simple percentage of max HR. It accounts for individual resting HR—someone with RHR 50 has a larger usable range than someone with RHR 80. Most coaches prefer Karvonen for serious training.

Question 2

What are the 5 heart rate zones?

Accepted Answer

Z1 Recovery 50–60%, Z2 Endurance 60–70%, Z3 Aerobic 70–80%, Z4 Anaerobic 80–90%, Z5 VO2max 90–100%. Z1–2 build base and fat oxidation; Z3 is tempo; Z4–5 improve speed and power. Fuel sources: Z1–2 primarily fat, Z3 mixed, Z4–5 primarily carbs. The 80/20 rule suggests 80% easy (Z1–2), 20% hard (Z4–5).

Question 3

What fuel source does each zone use?

Accepted Answer

Z1–2: primarily fat. Z3: mixed fat and carbs. Z4–5: primarily carbs (glycogen). Zone 2 is optimal for fat oxidation and building mitochondrial density. High-intensity zones deplete glycogen quickly. This is why Zone 2 training has become the #1 longevity trend—it builds metabolic flexibility.

Question 4

How much time should I spend in each zone?

Accepted Answer

The 80/20 rule: 80% of training in Z1–2 (easy), 20% in Z3–5 (hard). Elite Kenyan runners spend 85% in Zone 1–2. For weight loss, favor Z2 (60–80% of time). For speed, include Z4–5 (5–15%). Most recreational athletes overdo high intensity—more easy volume usually yields better results.

Question 5

Karvonen vs percentage of max HR—which is better?

Accepted Answer

Karvonen accounts for resting HR; more personalized. %MHR is simpler but less accurate for individuals with high or low resting HR. A 40-year-old with RHR 50 has different zone boundaries than one with RHR 80—Karvonen captures this. Use Karvonen for serious training; %MHR for quick estimates.

Question 6

What is Zone 2 training and why is it popular?

Accepted Answer

Zone 2 is 60–70% max HR (or 60–70% HRR + resting). Conversational pace. Dr. Peter Attia and others have popularized it as the #1 longevity trend—it builds fat oxidation, mitochondrial density, and aerobic base without excessive stress. Elite endurance athletes spend 80–85% of training here. It is the foundation of the 80/20 rule.

Heart Rate Zones — Karvonen & %MHR

Why This Stat Matters

Z1–Z5 • Zone 2 = Longevity • 85% Easy for Elites

Preset Profiles

Training Plan

Zone Ranges (Karvonen)

Recommended Time by Zone

🏅 Sports Records

📋 Key Takeaways

💡 Did You Know?

📖 How It Works

Karvonen Method

%MHR Method

Fuel Sources by Zone

🎯 Expert Tips

Prioritize Zone 2

Use Karvonen

80/20 rule

Match zones to goals

⚖️ Comparison Table

📊 Infographic Stats

📚 Official Sources

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Zone	%HRR	Fuel	Time %
Z1 Recovery	50–60%	Fat	10–20%
Z2 Endurance	60–70%	Fat	60–80%
Z3 Aerobic	70–80%	Mixed	10–20%
Z4 Anaerobic	80–90%	Carbs	5–10%
Z5 VO2max	90–100%	Carbs	<5%