Cardio & Peak Heart Rate Zones
Calculate Zone 4 (cardio, 80–90% HRmax) and Zone 5 (peak, 90–100% HRmax). Use these high-intensity zones to build VO₂ max, lactate threshold, and anaerobic power.
What Zone 4 (Threshold) Trains
Zone 4 sits around your lactate threshold — the intensity above which blood lactate accumulates faster than your body can clear it. Sustained work in this zone teaches the muscles and cardiovascular system to buffer and clear lactate more efficiently, raising the pace or power you can hold "at threshold" without a runaway acidosis response.
Prescription: intervals of 5–15 min at Zone 4 with 2–4 min easy recovery, total work 20–40 min, once or twice per week.
What Zone 5 (VO₂max) Trains
Zone 5 targets your maximal oxygen uptake (VO₂max) — the highest rate at which your body can consume and use oxygen. Work in Zone 5 stresses the entire oxygen delivery cascade: stroke volume, cardiac output, capillary density, and mitochondrial oxygen extraction.
Prescription: the classic 4 × 4 min protocol (4 min at 90–95% HRmax, 3 min easy jog, repeat 4 times) is one of the most-studied and most-effective VO₂max sessions, popularised by the Norwegian University of Science and Technology's cardiac rehabilitation research.
Reference: Helgerud J, et al. Aerobic high-intensity intervals improve VO₂max more than moderate training. Medicine & Science in Sports & Exercise. 2007;39(4):665–71.
Recovery Cost
Both zones are neuromuscular-taxing. A hard Zone 5 session requires 48–72 hours before another high-intensity effort; a threshold session, 24–48 hours. Sandwich them between easy Zone 1–2 days, and never stack them back-to-back if you value long-term progression over short-term feels.
Heart Rate Zones (reference: age 30, HRmax ≈ 187 bpm, Tanaka)
| Zone |
Name |
% HRmax |
BPM (age 30) |
Primary use |
| 1 | Recovery | 50–60% | 94–112 | Warm-up, recovery, active rest |
| 2 | Endurance | 60–70% | 112–131 | Aerobic base, fat oxidation |
| 3 | Aerobic | 70–80% | 131–150 | Tempo, aerobic capacity |
| 4 | Threshold | 80–90% | 150–168 | Lactate threshold intervals |
| 5 | Maximum | 90–100% | 168–187 | VO₂ max, neuromuscular power |
What Each Zone Feels Like (Talk Test)
- Zone 1 · Recovery: You can sing.
- Zone 2 · Endurance: You can hold a full conversation.
- Zone 3 · Aerobic: Speaking becomes noticeably harder.
- Zone 4 · Threshold: Only short phrases of a few words.
- Zone 5 · Maximum: Almost impossible to speak.
Frequently Asked Questions
How accurate are heart rate calculators?
Formula-based calculators typically estimate HRmax within ±10–15 bpm. They are accurate enough to structure training for recreational athletes but not a substitute for a supervised max test.
What is the Karvonen method?
Karvonen uses heart rate reserve (HRR = HRmax − HRrest). Target HR = HRrest + (Intensity% × HRR). It personalises zones by accounting for resting heart rate.
Should I use different zones for cycling vs running?
Your bpm targets stay the same, but heart rate response differs by sport. Cycling HR is typically 5–10 bpm lower than running at equivalent perceived effort due to the seated position.
Is Zone 2 the best zone for fat loss?
Zone 2 maximises the percentage of calories from fat, but higher intensities burn more total calories per minute. Long-term fat loss is driven by total weekly energy balance.
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