Resting heart rate, what the number on your watch really says about you

What is the resting heart rate and what does it say about you?

The resting heart rate is the number of heartbeats per minute, measured at physical and mental rest. It shows how many beats your heart needs in order to supply the body while it idles. Two quantities determine it. The stroke volume, that is how much blood is moved per beat, and the state of the autonomic nervous system.

That is exactly why the resting heart rate is interesting for physically active people. A trained heart pumps more blood per beat and gets by with fewer beats. The resting heart rate is therefore a rough mirror of the same adaptation that shows up more precisely in your maximum oxygen uptake.

At the same time it responds to everything that activates the sympathetic nervous system. Lack of sleep, alcohol the evening before, an infection, stress before a pitch. A single morning value therefore says little. The direction over two to four weeks says a lot.

Which resting heart rate is normal?

There is no official reference range for the resting heart rate, only measured distributions in population samples. In the US survey NHANES 1999 to 2008 the median for men between 20 and 39 years was 69 beats per minute, and 74 for women in the same age group. According to the same data, the middle 50 percent of men sat between 61 and 76 beats, and those of women between 66 and 82.

The frequently quoted rule that anything between 60 and 100 is normal does not hold up under closer inspection. The NCHS report places two competing definitions side by side. The traditional clinical convention draws the lines at below 60 and above 100 beats per minute, a revised version at below 50 and above 90. Under the traditional definition, according to the report, 15.2 percent of the men in the healthy comparison sample would have been bradycardic (95 percent confidence interval 14.1 to 16.4). A threshold that classifies every seventh healthy man as abnormal is no use as a verdict.

For Germany there is no comparably detailed percentile table. In 2019 the Gutenberg Health Study reported a mean resting heart rate of 68 beats per minute in men and 70 in women, for 15,010 people between 35 and 74 years. In the subsample without pre-existing conditions it was 65 in men and 69 in women. The study found no dependence on age within this age range.

Why women sit higher on average

Women have a measurably higher resting heart rate than men. In NHANES the mean for women aged 20 and over was 74 beats per minute, and 71 for men. The report puts the difference at 3 beats per minute and reports it as statistically significant in all adult groups up to 79 years. In its healthy subsample the Gutenberg Health Study found a difference of 4 beats. The direction is therefore stable, while the exact size varies with the study and the measurement method.

Is a low resting heart rate a good sign or a warning signal?

A low resting heart rate can mean two completely different things, and the number alone does not tell them apart. In trained endurance athletes it is the expression of an efficient heart. In others it can be a bradycardia that needs treatment, for instance from a disorder of the sinus node, an AV block, an underactive thyroid or as a side effect of medication.

The ESC guideline on cardiac pacing and cardiac resynchronization therapy of 2021 states the distinction clearly. Sinus bradycardia is physiological in certain situations, for instance in well-trained athletes, in young people and during sleep. And further, a sinus bradycardia of 40 to 50 beats per minute at rest or down to 30 beats during sleep may be accepted as a physiological finding, particularly in trained athletes, that does not require pacemaker therapy.

The decisive criterion is therefore not the number but whether symptoms come with it. The same guideline records that sinus node dysfunction only counts as an indication for a pacemaker if the bradycardia is symptomatic. As possible symptoms it names a range from mild fatigue through light-headedness and dizzy spells to near-fainting and fainting.

In practice that means the following. If you have been training endurance in a structured way for months, for instance with long training in the low intensity range, and your resting heart rate has fallen in parallel with your rising performance, the explanation is close at hand. If on the other hand your resting heart rate falls without anything having changed in your training, or if fatigue and dizziness come with it, that is not a training adaptation but a reason to have it checked.

When is a high resting heart rate a problem?

A high resting heart rate also has harmless and serious causes, and both look the same on the display. Fever, lack of fluids, caffeine, alcohol, acute stress and lack of sleep are harmless and temporary. Persistently raised values, on the other hand, can point to an overactive thyroid, anaemia or a cardiac arrhythmia.

The ESC guideline on supraventricular tachycardia of 2019 defines sinus tachycardia as a sinus rhythm above 100 beats per minute. It describes so-called inappropriate sinus tachycardia as a persistently fast sinus rhythm above 100 beats at rest or on minimal activity that is out of proportion to the actual load. As a typical Holter pattern it names a mean heart rate above 90 beats per minute over 24 hours.

The most important special case is atrial fibrillation. It often shows itself as an irregular, frequently fast pulse and remains free of symptoms in some of those affected. A wearable can raise a suspicion, but it cannot make the diagnosis. More on that below.

A single raised value is not a finding. A resting heart rate that persistently sits above 100 over weeks, measured under the same conditions, is one.

When should you have your resting heart rate checked by a doctor?

It is not the number that decides but the combination of value and symptoms. There are warning signs for which you should seek medical advice regardless of the measured pulse, and there are constellations for which an appointment with your GP or a cardiologist makes sense. The following split does not replace an examination, it only helps with the classification.

Seek medical help immediately, in case of doubt via the German emergency number 112.

• Fainting or near-fainting, especially without a recognisable trigger
• Pressure, tightness or pain in the chest
• Shortness of breath that is new or worsens rapidly
• Palpitations or a racing heart together with dizziness, nausea or cold sweats
• A pulse that suddenly feels irregular and does not become even again on its own

Arrange an appointment soon.

• Resting heart rate persistently above 100 beats per minute over several weeks, without an infection and without a recognisable trigger
• Resting heart rate below 50 beats per minute if you do not do regular endurance sport
• Resting heart rate below 50 together with fatigue, light-headedness, a drop in performance or dizziness, even if you do train
• A change of more than 10 beats per minute over weeks that cannot be explained by training, illness or sleep
• A wearable that repeatedly reports an irregular rhythm

This list is a guide for the conversation, not a diagnosis. Whether a value needs checking depends on your history, your medication and the examination findings, and that can only be judged in a doctor's office.

How do you measure your resting heart rate correctly?

The most informative moment is in the morning right after waking, still lying down, before the first coffee and before you look at your phone. More important than the perfect moment is that you always measure under the same conditions. Otherwise you are comparing daily form with measurement error.

To measure it yourself, place your index and middle finger on the inside of your wrist, below the thumb. Do not use the thumb, it has a palpable pulse of its own. Then count for 30 seconds and double it, or better count a full minute, because that also reveals irregularities.

A look at the reference data is worthwhile, because their measurement conditions show how strictly defined such a value actually is. In NHANES the pulse was palpated seated at the radial artery over 30 seconds after about four minutes of sitting quietly, and doubled. In the Gutenberg Health Study it was measured oscillometrically, seated, after 5, 8 and 11 minutes of rest, using the mean of the second and third measurement. Two serious studies, two different procedures. Anyone comparing their morning value taken lying down with such tables is for that reason alone not comparing exactly.

How accurately does your smartwatch measure the resting heart rate?

The value from your wearable is an estimate, not a measured heartbeat. Watches and fitness trackers on the wrist work optically, with photoplethysmography. They shine light into the skin and work back from the reflected light to fluctuations in blood volume. An ECG, by contrast, measures the electrical activity of the heart directly. These are two different things that mostly deliver the same result and sometimes do not.

How large the difference is was quantified by a study in npj Digital Medicine in 2020 in 53 people against an ECG patch. At rest the mean absolute error of the consumer devices tested was 7.2 beats per minute with a standard deviation of 5.4. The spread between devices was large, the most accurate came in at 4.4 beats, the least accurate at 10.2. During movement the error rose to an average of 10.2 beats. The authors found no statistically significant difference between skin types, but clear differences between devices and activities. A published methodological comment on this work exists, so the numbers are not uncontested.

A validation in JMIR mHealth and uHealth from 2019 over 24 hours against ambulatory ECG arrived at a mean absolute percentage error of 3.12 percent during sleep and 7.21 percent while sitting for an Apple Watch 3. That study, however, had only a single participant and is therefore not a statement about a population but a single-case validation. The evidence on everyday accuracy at rest is on the whole thinner than the matter-of-factness with which we read these numbers off every day would suggest.

The practical consequence is simple. Use the wearable value as a trend over weeks, not as a measurement for a single morning. And do not expect a diagnosis from it. The ESC guideline on atrial fibrillation of 2024 is unambiguous on this point. It requires ECG documentation for the diagnosis and states explicitly that wearables without an ECG function, which typically work with photoplethysmography, are not sufficient for it. The corresponding recommendation carries class of recommendation I and level of evidence A. A hint from your watch is a reason for an appointment, not a finding.

What does the resting heart rate say about your life expectancy, and what does it not?

A higher resting heart rate is associated with higher mortality in population studies. A meta-analysis in the Canadian Medical Association Journal from 2016 pooled 46 prospective cohort studies with 1,246,203 people and 78,349 deaths. Per 10 beats per minute more, the relative risk for all-cause mortality was 1.09 (95 percent confidence interval 1.07 to 1.12) and for cardiovascular mortality 1.08 (1.06 to 1.10). Those above 80 beats per minute had a relative risk of 1.45 for all-cause mortality compared with the lowest category.

Now the classification that is missing from most advice pieces. First, the authors themselves report considerable heterogeneity between the studies and a demonstrated publication bias. Second, and this is the remarkable point, the same authors record that the resting heart rate was not recommended as a measure in the American and European guidelines on cardiovascular risk estimation of the time. An association at population level is simply not the same thing as a usable risk marker for an individual person.

Third, the relationship is not simply linear and open-ended downwards. In 2019 the Gutenberg Health Study found a J-shaped course in 15,010 people, with the lowest mortality risk at 64 beats per minute. Above that value the hazard ratio per 10 beats was 1.30 (1.19 to 1.41), below it 1.36 (1.06 to 1.76). The claim that lower is always better cannot be derived from this.

And fourth, the classic resting heart rate may not even measure the right thing. In the Copenhagen Holter Study in 653 people between 55 and 75 years with no apparent heart disease, only the night-time heart rate remained as a predictor after full adjustment for cardiovascular risk factors, with a hazard ratio of 1.17 (1.05 to 1.30). The daytime resting heart rate and the 24-hour heart rate lost their predictive power. There it was measured by long-term ECG in a 15-minute window between 2 and 2:15 in the morning, not by wearable, so transferring this to smartwatch night-time values is an extrapolation.

That is also why there is no table here that translates resting heart rate values into years of life. Such tables are in circulation, but there is no sound source they could come from. Anyone who wants to know where they stand cardiovascularly cannot avoid measures that are actually used in risk estimation, for instance the number of atherogenic lipoproteins in the blood. You will find further articles on this in our English blog.

How do you lower your resting heart rate?

Regular endurance training is the best-documented lever. A meta-analysis in the Journal of Clinical Medicine from 2018 evaluated 191 studies with 215 samples. For endurance training, across 121 comparisons with 2,924 people training, the resting heart rate in the intervention groups fell on average from 72.4 to 68.0 beats per minute, a decrease of 6.0 percent according to the pooled data, while the control groups barely changed. The standardised mean difference was minus 0.33 (95 percent confidence interval minus 0.40 to minus 0.26).

Two details from the same work are relevant in practice. Strength training alone lowered the resting heart rate only weakly across all studies and not significantly in several subgroups. And the effect depended on the baseline value. The higher the resting heart rate before training, the larger the decrease. So anyone starting at 55 should not expect a dramatic change, while anyone starting at 80 rather should.

For practice that means plenty of volume at low intensity beats sporadic hardness. That is the same training range we described in the article on zone 2 training, and the same one that a solid competition preparation such as building up Hyrox training is based on. Incidentally, the number of training sessions during the interventions was not a significant factor influencing the change in the meta-analysis, which argues against the idea that more sessions are automatically better.

Everything else is less well documented. Less alcohol, more sleep and less caffeine are plausible through the same autonomic mechanisms, but the evidence for them is considerably thinner than for endurance training. And one important caveat at the end. A high resting heart rate can be the expression of a treatable illness. The authors of the meta-analysis point out themselves that training only works as an approach once such causes have been ruled out, for instance anaemia or an overactive thyroid. Do not train against a value whose cause you do not know.