Resting heart rate. What it is and what information it provides.

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The resting heart rate is not a new fact, it has been with us for many, many years, and it has never been difficult to know, you simply had to take your heart rate as soon as you got up, and we didn't even need any devices. It was as simple as taking your pulse by putting a finger on your wrist, as you were probably taught to do at school (at least I learned how to do it there).

But with the numerous arrival of watches equipped with optical pulse sensors, capable of taking pulse data over 24 hours, it has become more relevant. These devices allow not only to record your heart rate while you are doing sports, but also while you are travelling in the metro, drinking a beer or working (yes, also when you are doing THAT... you know what I mean).

This is when your doubts start. Is this information useful? What can I do with it? What is the use of knowing my heart rate at rest?

So since you have questions, I have answers. Let's go with them!

What is a resting heart rate?

The resting heart rate is the lowest number of beats per minute that you have while you are awake and at rest. It is not, therefore, the heart rate while you are sleeping, which is usually much lower than usual.

Usually the best time of day to take your pulse and know your resting heart rate (also known as RHR) is in the morning, right after waking up and while lying in bed.

If you want to keep a constant record of your RCF over different days, you should always take it in the same condition, so before you get up to drink your coffee, remember to take your pulse so you can write it down later.

What is the purpose of knowing your resting pulse?

Your resting heart rate is one of the best indicators of assimilation of training. When your resting heart rate decreases as a result of training, it is a sign that you are improving your aerobic capacity (because you are increasing the size of your heart). But above this, monitoring your HRF will help you to know how much fatigue you have accumulated and when you might be too tired, knowing whether you should rest or whether you can hit it hard during the day's training.

For this it is necessary to control our pulse at rest and, as I say, always do it in the same conditions so that the data is comparable. The importance is not in a specific data, which by itself is not worth anything. If today you take your heart rate at rest and it gives you 55 beats per minute, what do you do with the data? Nothing, because without being able to compare it with something else it does not tell us anything.

The value of all this is the daily record and therefore the trend over time. This is when we can know more about our physical condition, whether we are training well or if you are overdoing it, or if you are catching a virus or have a fever. To give you an example, I know that my usual resting heart rate is between 46-48 beats per minute. If I train hard, I also know that the next day my resting pulse will increase, hovering around 53-54 beats per minute. If I have been training hard for a week and I am in that range or slightly higher, I can also recognize that this is a normal state.

But if I'm not doing intensity training and my resting pulse goes up to that range or above, I can tell that something is wrong. It may indicate that there is an injury, that I'm about to get sick, fever, general tiredness or stress. By the time I get to 58-60 resting pulses I have to ask myself what can cause that rise in pulse rate.

What you should not do is compare your resting CF with anyone else's. You are a unique specimen, with a unique training and physical characteristics. Your fatigue partner's CF may be lower, but it is not indicative of anything or it may be for 20 different reasons. Remember, it is your tendency over time that is important.

How do you take your resting heart rate?

You know, the best time to take your RCF is in the morning in bed, as soon as you wake up and before you get up. You can do it the traditional wayby putting your fingers on your wrist and keeping an eye on a stopwatch. Although today there are technology cheap enough to automate that process a little bit.

If you're around, though, it's because you're interested in sport-focused technology. I'm sure you already have at least one heart rate monitor at home. You'll simply have to put the sensor on your chest, relax for a minute and see on the screen which is the lowest reading that appears while you're lying down. That will be the value you'll have to write down as your resting heart rate for that day.

Using optical sensors to have the pulse at rest automatically

Let's face it: we are very lazy. That the first thing we have to do in the morning is to take our RCF and write it down is not what you want to do as soon as you wake up. As always, technology comes to fill in the gaps. In this case, to compensate our laziness or to free our mind from one more routine task.

With the rise of optical pulse sensor devices, another function is to monitor the heart rate throughout the day, recording all these data and trends associated with our movement and rest. Of course, this includes recording our pulse at rest.

But if you've read this far, you'll remember that we agreed that the resting heart rate is the lowest register while you're awakeHow is a device able to differentiate between the periods of being awake and being asleep? This is where the issue (which until now was very simple) starts to get complicated.

Collecting data

It depends on the manufacturer and how he has prepared the algorithms specifically. Some will not differentiate the sleep period and simply look for the lowest register of the day. Others will forget the lowest value and look for an average over a certain time or an average of the lowest values of the day.

In the case of those who do average, we get back into somewhat swampy terrain. What's the refresh rate they have? I mean, how often do they take heart rate records? Some manufacturers have a fairly solid recording period, like Fitbit that does it every 5 seconds when you're not recording a specific sport.

Others go to the other extreme, for example the Apple Watch records the pulse every 10 minutes, regardless of what you do in that period of time. You can do an interval at 3:00 min/km going up to 185 beats per minute, which if you are not recording the activity, it may not be recorded anywhere. The reason is none other than not to impact the battery too much.

Garmin, for example, opts for an intermediate solution: varying the recording rate depending on whether there is movement or not. If you are not moving, it will extend the pulse reading range. If you are moving, it will shorten it. However, it lacks an option that allows us to decide for ourselves whether we want to sacrifice autonomy in exchange for greater precision in obtaining data. Garmin fills its watches with options and customisations, but sometimes it leaves the most elementary things on the table.

Therefore not only the accuracy of the optical sensor is important, but also the frequency with which it records data.

Devices that allow it

Today the list of devices that already allow to do this heart rate monitoring is already quite extensive, and what is about to come, because if a year ago optical sensors were becoming an option for the immediate future, most probably within a year all watches will incorporate an optical pulse sensor by default. All brands already have it in their catalog in one form or another, Suunto being the last one to arrive as it will have a Spartan Sport with optical measurement with Valencell sensor by the end of the year (although it is not clear if it will monitor pulse during 24 hours).

As of the date of this article, these are the devices that support it. As I say, in the next months more models will be added to this list until it becomes something totally standard (do you remember when the activity monitor was a novelty?), so if you arrive here in five months and you don't find a device in the list, you can notify it in the comments and I will add it to the list (if I haven't remembered to do it before):

Fitbit Blaze
Fitbit Charge HR
Fitbit Surge
Garmin Forerunner 235
Garmin Forerunner 735XT
Garmin Fenix 3 HR
Garmin Vivoactive HR
Garmin Vivosmart HR
Garmin Vivosmart HR+
TomTom Runner 2

There are other smart watches like the Motorola Moto 360 Sport or Apple Watch that also incorporate it, but they go in a different direction from the type of product I usually deal with on the page.

These other devices, despite having an optical pulse sensor, do not offer constant HR monitoring. Whether or not they do in the future remains to be seen.

Adidas miCoach Smart Run - The sensor is of Mio (Philips) origin, and only supports pulse measurement during training. You will not receive constant measurement update.
Garmin Forerunner 225 - Identical to Adidas. With its Mio origin sensor the measurement during exercise is very good, but there is no possibility of measuring the rest of the day.
Polar A360 - Right now the Polar optical sensor does not offer this function, but the Finns have indicated that they will incorporate it.
Polar M600 - Identical to the previous case, although with a renewed sensor.
External optical sensors - I am referring to "passive" sensors that simply send heart rate data. That is, Mio products (Mio Link, Alpha, Fuseetc.) and Scosche RHYTHM+. They are not "smart" devices nor do they have memory capable of storing data, so even if the sensor would allow it, the device cannot.
Suunto Spartan Sport - At the moment the only thing we know is that the sensor will be from Valencell (same manufacturer as Scosche RHYTHM+) and it is not clear if it will support the function. So for the moment it will remain in this "not supported" section.
TomTom Runner Cardio - The first version of the Optical Sensor Runner featured an optical sensor from Mio. And as you've seen, there's no chance of it supporting it.

Remember that you can find all the information about the above devices and their optical pulse sensor in the test section of the page.

Use it to your advantage

Now that you know what you can do by knowing your resting heart rate and how you can do it, it's up to you to use it to your advantage. So, constantly monitor yourself to be able to identify what is normal and what is not and to be able to determine if it's a good day for an intense workout or if it's better to take it easy. Or even if you're on the verge of getting sick and it's better to keep warm.

You need an adjustment period. It is not by taking the data for three days in a row and then starting to make decisions based on the result on the fourth day. You need to record the data continuously to have a clear trend of what your usual minimum frequency is. Also be careful when you make a change of device or recording method (i.e. from the manual method to an optical sensor watch, for example), to assess how the change may have affected your daily recording.

And with that... thanks for reading!