Heart Rate Training Zones

Overview

Heart rate training zones translate effort into numeric ranges you can chase on a watch or chest strap. By splitting maximum heart rate into five bands — recovery, easy aerobic, tempo, threshold, and VO2 max — coaches give athletes a way to spread their training stress across the right intensities, rather than living perpetually in the murky grey zone between easy and hard.

For runners and cyclists especially, zone-based training is the foundation of polarised programmes: a lot of work in zones 1 and 2, a small amount of true high-intensity work in zones 4 and 5, and relatively little time in the middle. Even casual exercisers benefit from knowing whether a steady-state session is genuinely easy or sneakily moderate.

How it works

Maximum heart rate is approximated by HR_max = 220 − age, the classic Fox formula. A more accurate alternative is Tanaka's 208 − 0.7 × age. When a resting heart rate (HR_rest) is supplied, the tool uses the Karvonen method to centre zones on heart rate reserve: target = HR_rest + intensity × (HR_max − HR_rest). Without HR_rest, it falls back to plain percentages of HR_max.

Zone bands are typically 50–60% for zone 1, 60–70% for zone 2, 70–80% for zone 3, 80–90% for zone 4, and 90–100% for zone 5. These are training-stress proxies — the actual physiology of fat versus carbohydrate burn shifts at thresholds that are individual and may not exactly match the bands. A lab or field test (lactate, FTP, threshold heart rate) refines the boundaries for serious athletes.

Examples

• A 30-year-old with no HR_rest: HR_max ≈ 190. Zone 2 sits between 114 and 133 bpm.
• A 40-year-old with HR_rest 55 using Karvonen: HR_max ≈ 180; zone 4 at 80–90% reserve gives 55 + 0.8 × 125 to 55 + 0.9 × 125 = 155 to 168 bpm.
• A 50-year-old using Tanaka: HR_max ≈ 173. Zone 5 starts around 156 bpm.
• A 25-year-old recovery jog: HR_max 195; zone 1 (50–60%) is 98 to 117 bpm — easy nasal-breathing pace.

FAQ

Which formula should I use?
Tanaka is slightly more accurate on average. Karvonen with measured HR_rest is more individualised when available.

How do I find resting heart rate?
Measure first thing in the morning, lying still, for a full minute. Average across three to seven days.

Why does my watch disagree?
Watches often use a lactate threshold model or learned percentages rather than the textbook 220 − age. Both are estimates.

Is zone 2 really where fat burn happens?
Zone 2 maximises absolute fat oxidation in trained individuals, but total calorie burn matters more than the fuel mix for body composition goals.

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