Heart-Rate Zones Explained

What heart-rate zones are

A heart-rate zone is a band of beats per minute that a watch, chest strap or app labels with a name such as "easy," "moderate" or "hard." The bands are usually calculated as percentages of an estimated maximum heart rate, or of a "heart-rate reserve" (the gap between resting and maximum heart rate). The heart rate itself is measured; the zone boundaries are calculated, and the labels are a convention. This page explains what the numbers can and cannot tell you. It is information only and does not prescribe any training.

Measured, estimated and calculated

Why the age formula is only an average

The familiar rule "220 minus age" is a population average, not a measurement of any one person. A meta-analysis of 351 studies with 18,712 people, followed by a laboratory study of 514 healthy adults, produced a different equation, 208 minus 0.7 times age, and concluded that the older formula underestimates maximum heart rate in older adults. [1] In a study of adults with overweight or obesity, 220 minus age overestimated actual maximum heart rate in 20- to 40-year-olds (186 against a measured average of 180 beats per minute), while 208 minus 0.7 times age was the most accurate of the three equations tested. [2] Another small study of 18- to 25-year-olds found that men had a higher measured maximum than women and sedentary people a higher one than active people, so one age-only number hides real differences. [3]

Equations built from adult data are not suited to children; a systematic review concluded that adult age-based equations do not apply to them. [4]

Label: established that these formulas are rough averages with wide individual error.

Zones versus the body's own thresholds

Zones are meant to stand in for how hard the body is working. In a study of 112 people with coronary heart disease in cardiac rehabilitation, 55% had their ventilatory anaerobic threshold (a lab marker where breathing starts to change) outside the fixed percentage range used to set exercise intensity, and the correlation between predicted and measured values was weak (r = 0.32). [5] That is one clinical group, not everyone, but it shows why a percentage of an estimate may not match a personal threshold.

Medicines change the picture too. Beta blockers work by slowing the heartbeat, so zones built on a formula can be misleading for people who take them. [6] Ask the prescriber how to judge effort.

The talk test as a low-tech check

A review of the talk test found that comfortable speech is likely possible when exercise intensity is below the ventilatory or lactate threshold, and not likely possible above it. [7] The NHS describes moderate effort as being able to talk but not sing. [8] A systematic review in people with heart and lung disease supported its validity but cautioned that there is no single well-defined protocol, so results should be interpreted carefully. [9] For more on effort scales, see perceived exertion (RPE).

Public-health guidance in plain terms

The WHO fact sheet recommends at least 150 minutes of moderate-intensity physical activity per week for adults. [10] The NHS gives the same total and adds that vigorous activity makes you breathe hard and fast. [8] These are general population guidance, not a personal plan.

How to judge a zone claim

• Ask whether the maximum was tested or only calculated by age.
• Remember that a strap or watch can misread rate; see chest strap vs wrist heart rate.
• Treat labels such as "fat-burning zone" as a marketing claim unless a study of a clear outcome is cited.
• Compare with how you feel and what you can say, not only the number.

For resting-rate context see resting heart rate.