Understanding Heart Rate Zones
Heart rate zones are one of the most effective training tools available.
They help you understand how hard you're working, ensure you're training at the right intensity, and prevent the most common mistake in endurance sport — going too hard on easy days and not hard enough on hard days.
What Are Heart Rate Zones?
Heart rate zones are ranges of beats per minute (BPM) that correspond to different levels of effort. Each zone produces different physiological adaptations. The most common model in triathlon training uses five zones:
Zone % Max HR and How It Feels
Zone 1 - 50–60% - Very easy. Fully conversational.
Zone 2 - 60–70% - Easy. Can hold a full conversation.
Zone 3 - 70–80% - Moderate. Short sentences only.
Zone 4 - 80–90% - Hard. Breathing heavily. Difficult to talk.
Zone 5 - 90–100% - Maximum. Unsustainable for long.
Why Zone 2 Matters Most
Most of your training should be in Zone 2. This might feel surprisingly easy, especially if you're used to pushing hard. But Zone 2 builds the aerobic base that everything else sits on. It's where your body learns to use fat as fuel and develops the endurance to go longer without fatigue.
The biggest mistake most triathletes make: drifting into Zone 3 on easy days (too hard) and not reaching Zone 4–5 when genuinely hard effort is called for (too easy). Polarise your training — easy should really be easy.
Finding Your Zones
The most accurate method involves a lab or field test. A simple starting estimate uses maximum heart rate:
Estimate max HR: 220 minus your age (a rough guide — individual variation is significant)
Apply the percentages from the table above
Through Tempr App, you can simply update your heart rate zones in their calculator and it will provide you with your zones
Over time, with more data from training, you'll develop a clearer and more personal picture of where your zones sit. Your Garmin or Apple Watch can also estimate zones from your training history.
In Practice
Once you know your zones, use them as guardrails:
Easy sessions: stay in Zone 1–2
Tempo or threshold work: aim for Zone 3–4
Intervals or race-pace efforts: Zone 4–5
Over time, you'll also develop a strong sense of effort that reduces your reliance on constantly checking a device. That internal calibration is one of the most valuable things you can build as an athlete.
Heart rate zones aren't about restriction. They're about training smarter — and making sure the easy days are doing their job.
Kye Simpson