Heart Rate Training Zones Explained

1. Finding Your Maximum Heart Rate

All heart rate training zones are defined as percentages of your maximum heart rate (MHR) — the highest number of beats per minute your heart can achieve during all-out effort. The most widely used formula for estimating MHR is:

Max HR = 220 − Your Age

For a 35-year-old, this gives an estimated MHR of 185 bpm. This formula has a standard deviation of ±10–12 bpm, meaning individual max heart rates can vary significantly. More accurate formulas include the Tanaka formula (208 − 0.7 × age) or the Gellish formula (207 − 0.7 × age), though the simple 220-minus-age remains the most practical for everyday use.

The only truly accurate way to determine your MHR is through a maximal exercise test conducted under supervision. For most recreational exercisers, the estimated formula is sufficient.

2. The 5 Heart Rate Training Zones

3. The "Fat Burning Zone" — Fact vs Myth

Zone 2 is often labelled the "fat burning zone" because at lower intensities, the body derives a higher proportion of energy from fat. At 65% of max HR, roughly 60–70% of calories burned come from fat. At 85% of max HR, fat contributes only 30–40% of calories burned.

However, this can be misleading. Because higher-intensity exercise burns significantly more calories per minute in total, the absolute amount of fat burned at higher intensities is similar or greater. A 30-minute Zone 3 run might burn 350 kcal, while a 30-minute Zone 2 walk burns 200 kcal — even though the walk uses a higher fat proportion.

For fat loss, total calorie expenditure matters more than the fat-burning percentage. Zone 2 training is valuable for building aerobic base, improving metabolic health, and enabling recovery — not because it burns uniquely more fat.

4. Zone 3 and Above: Cardio Fitness and VO₂ Max

Zones 3–5 train the cardiovascular system more intensively and are associated with greater improvements in VO₂ max (your maximal oxygen uptake — the gold standard measure of cardiorespiratory fitness).

Zone 4 training around the lactate threshold is particularly effective for runners and cyclists looking to improve race pace. High-intensity interval training (HIIT) alternating between Zones 4–5 and Zones 1–2 has been shown to produce large improvements in VO₂ max in a shorter total training time than steady-state exercise.

5. How to Use Heart Rate Zones in Practice

Most exercise science recommendations suggest that recreational exercisers should train with an 80/20 split: approximately 80% of training volume in Zone 1–2, and 20% in Zones 3–5. This polarised approach — endorsed by researchers and elite coaches — tends to produce better long-term fitness gains than training exclusively in the "moderate" Zone 3.

A common mistake is spending too much time in Zone 3 — the "moderate but uncomfortable" zone that is too hard to be recovery and too easy to drive peak fitness adaptations. Elite endurance athletes train significantly more in Zone 2 than most recreational athletes would expect.

6. Monitoring Your Heart Rate

Heart rate can be monitored using a chest strap monitor (most accurate), a wrist-based optical sensor (good for everyday use, less accurate during high-intensity intervals), or a pulse oximeter. Most modern fitness trackers and smartwatches provide continuous heart rate monitoring sufficient for zone-based training.

For accurate zone training, chest straps from brands like Polar, Garmin, or Wahoo are recommended — wrist-based sensors can lag by 10–15 seconds and may misread during rapid intensity changes.

7. Sample Weekly Training Plan by Zone