What are running Zones
Everyone talks about training in zones. Heart rate zone 2, threshold work, VO2 max intervals. It sounds technical, and honestly, most explanations make it more complicated than it needs to be. Here's the simple version, and the common mistake that keeps most runners stuck.
What Zones 1 – 5 Actually Mean
Heart rate zones divide your effort into five levels, from almost nothing to absolute maximum. Think of them as a spectrum from recovery to limit. Each zone targets different energy systems and drives different adaptations in your body.
The lower zones — 1 and 2 — are where you build your aerobic engine. The higher zones — 4 and 5 — are where you push your limits. Zone 3 sits in an awkward middle: harder than easy, not quite hard enough to drive real threshold adaptation. That's the zone most recreational runners spend almost all their time in.
Why "Run Slow to Get Faster" Actually Works
This sounds backwards. But it's one of the most well-established principles in endurance sport, and it's backed by decades of research and practised by every elite distance runner on earth.
Your aerobic base is built almost exclusively in zones 1 and 2 and is the foundation everything else sits on. A bigger aerobic base means you can sustain faster paces at lower effort, recover faster between hard sessions, and eventually run faster without your heart rate spiking. Zone 2 running builds mitochondrial density, fat oxidation, and cardiac output. These are the actual engines of endurance performance.
Elite marathoners run 80% or more of their weekly mileage at easy, conversational paces. The fast stuff is a small fraction of total volume. The slow stuff is where the real training happens.
The Biggest Mistake: Always Running Too Hard
Most recreational runners end up in zone 3 for almost everything. Not easy enough to build the aerobic base, not hard enough to drive genuine adaptation. It's the worst of both worlds, you accumulate fatigue without getting the training effect you actually need.
When I shifted from football to running, this was the pattern I fell into immediately. I knew how to suffer for 90 minutes on a pitch. I was comfortable at a certain level of effort. So I brought that same energy to running, and ran almost every session at a pace that felt "decent" not easy, not hard. Just medium.
Coming from football, I had decent cardio, but my legs couldn't handle the impact at the paces I was trying to run. Slowing down genuinely helped me build volume without breaking down, and after six weeks of mostly easy running, my threshold pace dropped noticeably. The data doesn't lie.
That medium zone feels productive because you're working. But it doesn't build your base and it doesn't stress your threshold enough to shift it. You stay stuck.
How to Find Your Zones
Two Ways to Find Your Zones
- Heart rate method: use the formula 220 minus your age as a rough max HR estimate, then calculate zone percentages. Better yet, do a field test, run as hard as you can for 30 minutes and take the average HR in the last 20 as your threshold.
- Feel/talk test: can you hold a conversation at this pace? Yes = zone 1–2. Short sentences only = zone 3. One word answers = zone 4. No talking = zone 5. It's that simple as a starting point.
- Wrist HRMs are inconsistent, a chest strap like Polar H10 is far more accurate if you want data you can actually trust.
Don't overthink the exact numbers. What matters is developing the habit of running easy when you should be easy, and genuinely hard when a session calls for it. That polarisation is the principle, the precise heart rate numbers are secondary.