The five-zone model explained
The %HRmax model splits effort into five bands, each a slice of your maximum heart rate. It is the simplest zone system: you only need one number (HRmax) to use it, which is why most watches and apps default to it.
Zone 1 (50–60%) is recovery. Zone 2 (60–70%) is the aerobic-base zone where fat oxidation and capillary density improve, most endurance volume lives here. Zone 3 (70–80%) is tempo. Zone 4 (80–90%) sits around lactate threshold. Zone 5 (90–100%) develops VO₂max in short, hard intervals.
How to use these zones
Follow the easy-hard rule: keep easy days genuinely easy (Zones 1–2) and hard days hard (Zones 4–5), avoiding the 'grey zone' of moderate-but-not-easy training. A common, evidence-backed split is roughly 80% of time easy and 20% hard.
Remember that heart rate lags effort by 1–3 minutes and drifts upward in heat, dehydration or fatigue (cardiac drift). For very short intervals, judge effort by pace, power or feel, heart rate simply can't respond fast enough.
When %HRmax falls short
Because it ignores your resting heart rate, %HRmax treats a very fit athlete and a beginner of the same age identically. The Karvonen (heart-rate reserve) method fixes that by factoring in resting HR, and LTHR-based zones anchor to your real threshold instead of an age estimate, both are more individual.
Worked example
For an athlete with a maximum heart rate of 185 bpm:
| Zone 1, Recovery (50–60%) | 93–111 bpm |
| Zone 2, Endurance (60–70%) | 111–130 bpm |
| Zone 3, Tempo (70–80%) | 130–148 bpm |
| Zone 4, Threshold (80–90%) | 148–167 bpm |
| Zone 5, VO₂max (90–100%) | 167–185 bpm |
Frequently asked questions
What heart rate zone burns the most fat?
Fat is the dominant fuel in Zones 1–2 (about 50–70% of maximum heart rate), where your body relies on aerobic fat oxidation. Higher zones burn more total calories but a greater share from carbohydrate. For building the fat-burning aerobic base, steady Zone 2 work is the most effective.
How long should I spend in Zone 2?
For most endurance athletes, the majority of weekly training, often 70–80% of total time, should be easy Zone 2 work. It builds aerobic capacity with low fatigue, letting you absorb the smaller dose of hard Zone 4–5 sessions that drive top-end fitness.
Why is my heart rate higher than my zones suggest?
Heart rate rises with heat, dehydration, caffeine, stress, illness and accumulated fatigue, and it drifts upward during long efforts ('cardiac drift'). If your numbers run consistently high, your maximum heart rate estimate may be too low; verify it with a field test rather than a formula.
Are heart-rate zones the same for cycling and running?
No. Running typically produces a maximum heart rate 5–10 bpm higher than cycling for the same person, because more muscle mass is active and you support your body weight. Set zones per sport, ideally from a sport-specific lactate-threshold heart-rate test.
Sources
- Tanaka, Monahan & Seals (2001). “Age-predicted maximal heart rate revisited.” J Am Coll Cardiol 37(1):153–156.
- American College of Sports Medicine. ACSM's Guidelines for Exercise Testing and Prescription, %HRmax intensity classifications.