How Intensity Zones Work
Easy, Moderate, and Hard — what they mean and why they matter.
By Just5K
Three Simple Zones
Just5K uses three intensity zones based on your heart rate: Easy, Moderate, and Hard. These are personalized using your age and resting heart rate from Apple Health.
Easy Zone
This is your comfortable pace. You can hold a full conversation. Most of your training — especially in weeks 1–3 — should be in this zone.
Easy zone builds your aerobic base, which is the foundation for all running fitness. Don't skip it.
Moderate Zone
You can talk in short sentences but not sing. This is where most of your running intervals will land. It's the sweet spot for building endurance.
Hard Zone
You can only say a few words at a time. You'll rarely need to be here as a beginner. If you find yourself in the hard zone, slow down — there's no shame in it.
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.