How Intensity Zones Work
Easy, Moderate, and Hard — what they mean and why they matter.
By Just5K
Forget the lab talk
In the world of professional sports, coaches use words like "thresholds" and numbered zones. For us, it's much simpler. Your heart has three gears. Understanding them is the key to never feeling like you're "dying" on a run.
Easy — the conversation gear
This is where the magic happens. You should be able to tell a friend a whole story without gasping. If you can't talk, you're not in the easy gear.
Most of your training — especially in weeks 1–3 — should be here. Easy effort builds the foundation for everything else. It's how you teach your body to breathe better while moving. Don't skip it just because it feels too easy.
Moderate — the short-sentence gear
You can talk, but only in short bursts. "It's… a nice… day." This is where most of your running intervals will land, especially in weeks 3–6. It builds your stamina without burning you out.
Hard — the "wait, slow down" gear
You can only gasp out single words. As a beginner, you almost never need to be here. If you find yourself in the hard gear, slow down. There is zero shame in it. In fact, slowing down is the fastest way to get fit, because it lets you train more often without getting hurt.
How Just5K knows your gears
Just5K reads your heart rate and sorts your effort into the three gears automatically. The boundaries are personalised using your age and your resting heart rate from Apple Health — so what counts as "easy" for you might not match what counts as "easy" for someone else.
As you get fitter, you'll notice the same pace produces a lower heart rate. Same effort on your side, less work for your heart. That's the foundation getting stronger.
Tip: The biggest mistake beginners make is running too fast. If you can't speak in short sentences, you're going too hard. Slow down and you'll actually improve faster.