Heart rate zones, aerobic and anaerobic threshold

Heart rate zones help you monitor the intensity of endurance training. Our bodies produce energy in different ways during exercise of different intensities, and the physiological effects of exercise on the body also differ.

To calculate your heart rate zones you need your maximum heart rate, which you can work out with a maximum heart rate calculator.

How heart rate zones are calculated

The heart rate zones in this calculator are calculated as percentages of maximum heart rate (%HRmax).

Heart rate zones are also often calculated using the formula published by Martti Karvonen in 1957, which takes the resting heart rate into account alongside the maximum heart rate. Including the resting heart rate makes the calculation adapt better to your individual fitness level.

The calculator also estimates the aerobic and anaerobic thresholds. As far as we know, there is no scientific evidence for using the Karvonen formula to estimate these thresholds, so the calculator uses a percentage of maximum heart rate for them. The same method is used for the heart rate zones, so that the zones and the thresholds are consistent with each other.

Many different zone divisions have been proposed: divisions into five and four zones, as well as a three-zone division based on the aerobic and anaerobic thresholds.

You can read more about the Karvonen formula and calculate the heart rate zones for health-enhancing physical activity it produces with the Karvonen formula calculator.

Heart rate zone descriptions

Zone 1: 50-60%
Very light exercise

energy production mainly from fat
training can be continued for a very long time
suitable for recovery training and for warming up and cooling down
mainly slow-twitch muscle fibers are used
easy to talk
example: warm-up

Zone 2: 60-70%
Light exercise

energy production mainly from fat
training can be continued for a long time
develops endurance fitness and the body's oxygen utilization capacity
usually makes up the largest part of total endurance training
mainly slow-twitch muscle fibers are used
reasonably easy to talk
example: long-duration run

Zone 3: 70-80%
Moderately strenuous exercise

energy production from fats and carbohydrates
the aerobic threshold usually falls in this zone
lactate formation increases
develops oxygen uptake and aerobic capacity as well as the body's ability to remove lactate
mainly slow-twitch muscle fibers are used, but the involvement of fast-twitch fibers also increases
talking becomes more difficult
example: brisk run

Zone 4: 80-90%
Heavy exercise

energy production mainly from carbohydrates
lactate formation increases
develops oxygen uptake and aerobic capacity as well as the body's ability to remove lactate
both slow-twitch and fast-twitch muscle fibers are used
talking is difficult
example: fast-paced running or interval training

Zone 5: 90-100%
Really hard exercise

energy production from carbohydrates
develops anaerobic energy production
the anaerobic threshold is exceeded and lactate formation is faster than the body's ability to remove lactate
both slow-twitch and fast-twitch muscle fibers are used
talking is really difficult
example: near-maximal interval training

Aerobic threshold

The aerobic threshold refers to the maximum exercise intensity at which the blood lactate level does not rise above the resting level. Once the aerobic threshold is exceeded, the blood lactate level begins to rise. In aerobic exercise, however, the removal of lactate from the body is more efficient than the production of lactate. Endurance properties are therefore better in the range between the thresholds than in the anaerobic range. The personal aerobic threshold varies greatly between individuals: measured thresholds have ranged from 60 to as much as 90 percent of maximum heart rate. Interpret the calculator result critically.

Anaerobic threshold

The anaerobic threshold refers to the maximum exercise intensity at which the production of lactate and the removal of lactate are in balance. When the anaerobic threshold is exceeded, more lactate is produced than the body can remove. This leads to rapid exhaustion, and the intensity level can often only be maintained for a few minutes. The anaerobic threshold is also individual: measured thresholds have ranged from 75 to as much as 97 percent of maximum heart rate. Interpret the calculator result critically.

Both the aerobic and the anaerobic threshold can be raised through training.

Published: 10.12.2024

Updated: 14.10.2026

The text is a translation from the original Finnish-language text.

Author of the original text

Lassi Honkanen
physiotherapist

Sources:

Cleveland Clinic. 2023. Heart Rate Zones Explained. https://health.clevelandclinic.org/exercise-heart-rate-zones-explained

Iannetta, D., Inglis, E. C., Mattu, A. T., Fontana, F. Y., Pogliaghi, S., Keir, D. A., & Murias, J. M. (2020). A Critical Evaluation of Current Methods for Exercise Prescription in Women and Men. Medicine and Science in Sports and Exercise, 52(2), 466–473. https://doi.org/10.1249/MSS.0000000000002147

Ignaszewski, M., Lau, B., Wong, S. & Isserow, S. 2017. The science of exercise prescription: Martti Karvonen and his contributions. British Columbia Medical Journal. https://bcmj.org/articles/science-exercise-prescription-martti-karvonen-and-his-contributions

Nummela, A., Hynynen, E., Mikkola, J. & Vesterinen, V. 2022. Kestävyysharjoittelu: tutkitulla tiedolla tuloksiin. Lahti: VK-Kustannus Oy.