In This Article
Key Takeaways
- The 5-zone model divides 50–100% of max heart rate into distinct training stimuli
- Zone 2 (60–70% max HR) builds aerobic base and mitochondrial density — elite athletes train here 80% of the time
- Zone 4–5 drives VO2 max improvements but requires adequate Zone 1–2 base and recovery
- The "gray zone" (Zone 3, 70–80%) is too hard to recover from easily, too easy to drive aerobic power gains
- Use Karvonen formula (Heart Rate Reserve) for more personalized zone calculation
Calculating Your Max Heart Rate
All heart rate zones are calculated as a percentage of your maximum heart rate (MHR). Two common formulas:
- Standard formula: MHR = 220 − age (simple, widely used, ±10–12 bpm SD)
- Tanaka formula: MHR = 208 − (0.7 × age) (slightly more accurate for adults over 40)
Example for a 35-year-old:
- Standard: 220 − 35 = 185 bpm
- Tanaka: 208 − (0.7 × 35) = 208 − 24.5 = 183.5 bpm
These are estimates. The actual MHR can only be determined by pushing to true exhaustion. Individual variation is significant — some people's true MHR is 15+ bpm different from the formula prediction.
Calculate Your Heart Rate Zones
Enter your age and resting heart rate to get personalized training zones.
The 5 Heart Rate Zones
Using a max HR of 185 bpm (35-year-old) as an example:
| Zone | % Max HR | bpm Example | Feel | Primary Fuel |
|---|---|---|---|---|
| Zone 1 — Recovery | 50–60% | 93–111 | Very easy, can sing | Fat (high %) |
| Zone 2 — Aerobic / Fat Burning | 60–70% | 111–130 | Easy, can hold a conversation | Fat + some carbs |
| Zone 3 — Tempo / Aerobic Power | 70–80% | 130–148 | Moderate, can talk in short sentences | Equal fat + carbs |
| Zone 4 — Lactate Threshold | 80–90% | 148–167 | Hard, breathing labored | Mostly carbs |
| Zone 5 — VO2 Max / Anaerobic | 90–100% | 167–185 | Maximum effort, unsustainable | Carbs (anaerobic) |
What Each Zone Does Physiologically
Zone 1 — Recovery (50–60% MHR)
Active recovery. Promotes blood flow to flush metabolic waste from previous hard workouts without adding training stress. Use for easy recovery days and warm-ups. Walking and very easy cycling are typical Zone 1 activities.
Zone 2 — Aerobic Base (60–70% MHR)
The most important zone for long-term cardiovascular health and endurance. Zone 2 training:
- Builds mitochondrial density — more mitochondria per muscle fiber = more aerobic capacity
- Increases fat oxidation capacity — teaches the body to use fat efficiently
- Improves cardiac stroke volume (amount of blood pumped per beat)
- Is sustainable for long durations and recovers quickly
You should be able to hold a full conversation in Zone 2. If you can't, you're in Zone 3. Most runners and cyclists spend too much time in Zone 3, thinking they're training aerobically, but they're actually in the less productive "gray zone."
Zone 3 — Tempo / Gray Zone (70–80% MHR)
Zone 3 is sometimes called the "gray zone" because it's too intense for quick recovery (like Zone 2) but not intense enough to drive maximum aerobic adaptations (like Zones 4–5). Occasional Zone 3 work is fine — it builds aerobic power and feels productive — but shouldn't dominate your training.
Zone 4 — Lactate Threshold (80–90% MHR)
Training at or near lactate threshold improves the speed at which you can sustain hard effort before lactic acid accumulates. This is the zone for tempo runs, threshold intervals, and half-marathon race pace for trained runners. Typically sustainable for 20–60 minutes. Requires 48–72 hours of recovery.
Zone 5 — VO2 Max / Anaerobic (90–100% MHR)
Short, maximal efforts that push cardiac output to its limit. Intervals of 3–5 minutes at Zone 5 are the most potent stimulus for VO2 max improvement. Can only be sustained for seconds to a few minutes. Requires 48–72+ hours of recovery and should be limited to 1–2 sessions per week maximum.
How to Use Zones in Training
| Goal | Recommended Zone Distribution | Session Example |
|---|---|---|
| General health / weight loss | 80% Zone 1–2, 20% Zone 3 | 4× weekly 45-min Zone 2 walks/jogs |
| Build aerobic base (beginner) | 90% Zone 1–2, 10% Zone 3 | 3× 60-min easy run, 1× 30-min brisk walk |
| Improve VO2 max | 80% Zone 1–2, 20% Zone 4–5 | 3× Zone 2 + 1× 4×4 min Zone 5 intervals |
| Race performance (half/full marathon) | 80% Zone 1–2, 10% Zone 3, 10% Zone 4 | 2 easy runs + 1 long run + 1 threshold session |
| Peak competition | 75% Zone 1–2, 5% Zone 3, 15% Zone 4, 5% Zone 5 | Polarized periodization approach |
The 80/20 principle: Elite endurance athletes consistently train ~80% of their volume at low intensity (Zones 1–2) and only ~20% at high intensity (Zones 4–5). Recreational athletes who do most of their training at moderate intensity (Zone 3) miss out on both the recovery benefits of Zone 1–2 and the performance gains of Zones 4–5.
The Karvonen Method (Heart Rate Reserve)
The Karvonen formula uses Heart Rate Reserve (HRR) to calculate training zones, which accounts for your resting heart rate and gives more personalized zones:
HRR = Max Heart Rate − Resting Heart Rate
Target HR = (HRR × Zone %) + Resting Heart Rate
Example: 35-year-old with MHR 185 and resting HR 55 bpm
HRR = 185 − 55 = 130
Zone 2 lower (60%): (130 × 0.60) + 55 = 78 + 55 = 133 bpm
Zone 2 upper (70%): (130 × 0.70) + 55 = 91 + 55 = 146 bpm
Compare to the simpler method: Zone 2 = 111–130 bpm. The Karvonen method gives a higher Zone 2 ceiling because it factors in a lower resting heart rate (a sign of fitness). For a less fit person with resting HR of 75, Zone 2 would be lower.
Frequently Asked Questions
The "fat burning zone" is Zone 2, roughly 60–70% of max heart rate. At this intensity, fat provides a larger percentage of fuel (60–70% of calories from fat vs ~40% at Zone 4). However, higher intensity zones burn more total calories per minute even though fat provides a lower fraction. For overall fat loss, total calorie deficit matters most — Zone 2 is valuable for building aerobic base and is very sustainable, not because it burns "more fat."
The most common formula is 220 − age. A more accurate formula is 208 − (0.7 × age) (Tanaka et al., 2001). Both have a standard deviation of ±10–12 bpm, meaning your actual MHR could be 15 bpm higher or lower than predicted. The most accurate method is a maximal exercise test (running or cycling to complete exhaustion), but this isn't practical for most people. A fitness tracker's recorded peak heart rate from a very hard effort is a reasonable real-world estimate.
Yes — Zone 2 builds mitochondrial density and aerobic base, which is the foundation all higher-intensity training is built on. Elite endurance athletes spend ~80% of their training in Zone 2. Most recreational athletes do too much "moderate" (Zone 3) training — the gray zone that's too hard for quick recovery but not intense enough to drive VO2 max or lactate threshold gains efficiently. Shifting more training to Zone 2 is the most common performance improvement recommendation from exercise scientists for recreational athletes.
Both are useful and complement each other. Heart rate zones are objective but lag behind actual effort by ~30–60 seconds and are affected by temperature, hydration, caffeine, fatigue, and stress. RPE (Rate of Perceived Exertion, 1–10 scale) is immediate and captures perceived difficulty directly. Using both — targeting a zone while cross-checking with how you feel — gives the most accurate training guidance. On hot days or when fatigued, HR will run higher than usual for the same effort, so RPE helps you avoid overcooking the session.