Training science6 min read
Heart Rate Zones, Explained for Runners
What the five heart rate zones actually mean, how to find yours without a lab test, and how to use them to train smarter — not harder.
Most amateur runners train too hard on easy days and too easy on hard days. Heart rate zones fix that — they give you an honest, body-based picture of how much stress a run is really putting on your system.
The five zones
- Zone 1 — Recovery (50–60% max HR). Conversation feels effortless. Used to flush out fatigue.
- Zone 2 — Aerobic base (60–70%). Comfortable, sustainable, the foundation of endurance.
- Zone 3 — Tempo (70–80%). 'Comfortably hard' — sustainable for ~60 minutes.
- Zone 4 — Threshold (80–90%). Hard, breathing heavy, sustainable for ~20–30 minutes.
- Zone 5 — VO₂ max (90–100%). All-out intervals lasting seconds to a few minutes.
Finding your zones without a lab
The 220 − age formula is a rough starting point. A better one: run a hard, controlled 20-minute time trial, take your average HR, and treat that as your threshold. Your zones build out from there.
How KYN uses them
KYN prescribes each workout in a zone (or its RPE equivalent), then watches your data after the run. Drifted higher than expected? The next session gets dialled back. Felt easier than planned? The week ramps up.