Heart Rate Zone Training Simplified
5 zones, each with a purpose. Most of your training belongs in Zone 2. Here's the no-nonsense breakdown.
The Simple Version
Forget memorising 5 zones with exact percentages. In practice, you need to know three things: easy (can talk freely — Zone 2), hard (can barely speak — Zone 4-5), and everything in between (Zone 3 — the "grey zone" you should mostly avoid). Run easy 80% of the time, hard 20% of the time, and skip the middle.
The 5 Zones
Recovery
Very easy
How it feels
Walking pace. No exertion. Could do this all day.
Active recovery, warm-up, cool-down. Promotes blood flow without adding training stress.
Aerobic Base
Easy
How it feels
Can hold a full conversation comfortably. Feels almost too easy.
Builds your aerobic engine — mitochondria, capillaries, fat oxidation. This is where 80% of your training should live. The most underrated and most important zone.
Tempo
Moderate
How it feels
Can speak in short sentences. Comfortably uncomfortable.
Improves lactate clearance. Useful for tempo runs and sustained efforts. Often called the "grey zone" because it's hard enough to fatigue you but not hard enough to maximally stimulate adaptation.
Threshold
Hard
How it feels
Can only speak a few words. Breathing is heavy. Sustainable for 20-60 minutes max.
Pushes your lactate threshold higher — the pace you can sustain for a long race effort. Very effective for performance but costly on recovery.
VO2 Max
Maximum
How it feels
Can't speak. All-out or close to it. Sustainable for 3-8 minutes.
Improves maximum oxygen uptake. Interval training territory. Highly effective but highly fatiguing — use sparingly (1x per week max).
Example Week (4-5 Runs)
Notice how most days are easy. The one quality session is where the real work happens.
| Day | Session | Zone | Duration |
|---|---|---|---|
| Monday | Easy run | Zone 2 | 30-45 min |
| Tuesday | Quality session | Zone 4-5 | Intervals or tempo |
| Wednesday | Easy run or rest | Zone 1-2 | 20-30 min |
| Thursday | Easy run | Zone 2 | 30-45 min |
| Friday | Rest | — | — |
| Saturday | Long run | Zone 2 | 60-90 min |
| Sunday | Easy run or rest | Zone 1-2 | 20-30 min |
Zone 2 Is King
If you only take one thing from this article: run more in Zone 2. It feels too slow, but it's where your aerobic engine is built. The best runners in the world spend most of their time here.
Avoid the Grey Zone
Zone 3 is seductive — it feels productive but sits in a no-man's land. Too hard to recover from easily, too easy to maximally stimulate improvement. Polarise your training: easy or hard, skip the middle.
Listen to Your Body
Heart rate is a guide, not a dictator. Hot weather, caffeine, stress, and sleep all affect heart rate. If your Zone 2 feels hard today, slow down further. The effort should feel right, regardless of what the number says.