Run slower to run faster: this is zone 2

There's a belief deeply rooted among everyday runners: if you don't finish your session with your tongue on the floor, it didn't count. It sounds like effort and sacrifice, it plays very well, and it is, I'm sorry to say, one of the reasons you've been stuck at the same pace for two years. Most of your kilometres should be comfortable. Boring, even. Welcome to zone 2.

What zone 2 actually is

Zone 2 is a gentle aerobic intensity, the one where your body draws mainly on fat for fuel and you could hold a conversation without running out of breath. Neither a stroll nor a suffer-fest: a pace you could sustain for a long time without things turning ugly.

In heart-rate terms it sits at roughly 65-75% of your maximum. But if you haven't got a monitor, or you don't quite trust the one on your wrist, there's an older and more reliable method than you'd think.

The talk test: your free heart-rate monitor

It's as simple as it sounds: if you can speak in full sentences while running, even slightly broken ones, you're in zone 2. If all you can manage is the odd word between gasps, you've gone too hard. And if you can belt out the whole chorus without breaking sweat, you may have gone too easy.

The first time you try it you'll feel ridiculously slow. That's normal, and you'll probably be overtaken by someone walking their dog. That small blow to the ego is, oddly enough, the hardest part of zone 2 training.

The mistake of living in zone 3

Here's the trap half the park falls into every evening: always running at a middling pace, neither easy nor fast. It's called zone 3 and it's a treacherous place, because it hurts enough to make you feel like an athlete but delivers neither the benefits of an aerobic base nor the stimulus of real speed. Plenty of fatigue, very little training.

The logic of polarised training, followed by everyone from the weekend runner to the elite, points the other way: around 80% of your kilometres very easy, so that the remaining 20% can be genuinely intense. And that hard 20% is only possible if the 80% was truly easy.

Easy days properly easy. Hard days properly hard. The problem is the grey in between, where nothing gets trained.

Principle of polarised training

Be patient: it takes time, but it arrives

Going slowly won't pay off next Tuesday. What zone 2 does is build the engine under the bonnet: more capillaries, better use of fat, a heart that pumps more efficiently. That takes weeks and months, not days. But when it arrives, it arrives properly: one day you glance at your watch after a comfortable run and discover that the pace which seems impossible today has become your new easy pace.

So next time you head out, park the ego, drop the pace and talk to yourself out loud if you have to. You'll be running slower than ever and, a few months from now, faster than ever.