05/10/2026
What actually are your heart rate zones?
Your Garmin, Apple Watch or Whoop gives you zones, but where do they come from? Most wearables start with an estimate of your max heart rate (often a version of 220 minus age) and split it into percentages. Some adjust over time, but they’re still estimating, not measuring.
That estimate can be off by 10–20 bpm. Your watch says Zone 2, but you might really be in Zone 3, and you’ve been training in the wrong place for months.
Zones aren’t really about heart rate. They’re about what your body is doing at that intensity:
🟢 Zone 1–2: Mostly fat as fuel, easy breathing, can hold a conversation. This builds your aerobic base.
🟡 Zone 3: The grey zone. Harder than it feels, but not hard enough to drive big adaptations.
🟠 Zone 4: Around your threshold. Carbs take over, breathing gets heavy, and you can only hold it for so long.
🔴 Zone 5: Max effort. Short, sharp, and it hurts.
Your physiology sets the boundaries between zones, specifically your ventilatory or lactate thresholds. Two people of the same age can have completely different zones.
Your wearable is a great tool, but it’s only as good as the numbers you give it. A VO₂ Max test measures exactly where your thresholds sit. Plug those into your watch and every session has a real target.
📍 Input Performance, Wi******er.
