Training Science
Understanding Heart Rate Training Zones: Zone 1-5 Explained
Last updated: January 2025
Heart rate training is one of the most effective ways to structure your running. By training at the right intensity for each workout, you build fitness efficiently while avoiding overtraining. Here's what each zone means and how to use them.
How to Calculate Your Heart Rate Zones
There are two methods:
- Formula method: Max HR = 220 - age. Then calculate zones as percentages of max HR.
- Field test: Run a hard 5K or perform a 20-minute time trial. Your average heart rate during the final 10 minutes is approximately your max HR.
The Five Zones
Zone 1: Recovery (50-60% of Max HR)
Very easy effort. You can hold a full conversation without breathing hard. This zone is for recovery runs and warm-ups. It promotes blood flow to muscles without adding training stress.
Zone 2: Easy / Aerobic (60-70% of Max HR)
Comfortable effort where you can speak in full sentences. This is the most important zone for endurance runners. 80% of your training should be in Zone 2. It builds mitochondrial density, capillary networks, and fat-burning efficiency.
Zone 3: Moderate / Tempo (70-80% of Max HR)
Comfortably hard effort. You can speak in short phrases but not full sentences. This zone improves your lactate threshold — the point at which fatigue accelerates. Tempo runs and marathon pace work fall in this zone.
Zone 4: Hard / Threshold (80-90% of Max HR)
Hard effort where you can only say a word or two. This zone is for interval training and race-pace workouts. It improves your VO2 max and running economy at race intensities.
Zone 5: Maximum Effort (90-100% of Max HR)
All-out effort. You cannot speak. This zone is for short sprints and finishing kicks. It trains your neuromuscular system and peak power output. Use sparingly — no more than 5% of total training volume.
The 80/20 Rule
Research by Stephen Seiler shows that elite endurance athletes spend approximately 80% of training at low intensity (Zone 1-2) and 20% at moderate to high intensity (Zone 3-5). This distribution optimizes performance while reducing injury risk. Recreational runners often make the mistake of training too hard on easy days and too easy on hard days.
Heart Rate vs. Pace
Both methods have advantages. Pace is objective and doesn't vary day to day. Heart rate accounts for daily variations in fitness, fatigue, weather, and stress. Most coaches recommend using pace for structured workouts and heart rate for easy runs.
Calculate Your Training Zones
Use the training zone calculator to get personalized pace zones based on your recent race results. The calculator uses the 80/20 rule to give you the right paces for each zone.