Measure your resilience with Heart Rate Variability using your smartphone


In our day and age many of us have to deal with a growing load of information and chronic stress. Dealing with this can be very challenging and requires us to actively manage the amount of information and stress we take in each day. One very helpful resource in this can be measuring your Heart Rate Variability. Let’s take a look at what Heart Rate Variability is and how it can help you.

What is Heart Rate Variability?

Heart Rate Variability (HRV) is a way to look into the functioning of your autonomic nervous system (ANS). The autonomic nervous system is essential in surviving and thriving: it regulates your heart rate, respiration, digestion and many other vital functions. If you want to understand more about the role of your autonomic nervous system in resilience and well-being, read these free ebook chapters . For now, it is important to know that the ANS has two parts: a ‘gas pedal’ (sympathetic nervous system or SNS) and a ‘brake pedal’ (parasympathetic nervous system or PNS). The gas pedal is responsible for mobilization and the well-known ‘fight/flight’, the brake pedal is responsible for ´rest and digest´ functions.


An overview of the autonomic nervous system. On the left you see the parasympathetic nervous system and which organs it innervates, on the right the same for the sympathetic nervous system. Note how both parts of the autonomic nervous system influence almost all the same organs, but in opposite ways (decreasing/increasing).


These two parts of the ANS influence all vital parts of your organism to keep you alive. Relevant to HRV is that both the gas pedal and the break influence our heartbeat. Contrary to what you might think, when our heart beats with, say, 65 Beats Per Minute (BPM) it actually does not consistently beat at this speed. It has a certain variation in the time of each interval between heartbeats. This is Heart Rate Variability and it is produced by the effect that the brake pedal (PNS) has on your heart rate. This is also called vagal tone, since the parasympahetic nervous system influences your organs via the ‘vagus nerve’.


This is a basic representation of your HRV in a graph. Between every heartbeat is an interval of variable length (in milliseconds). HRV is calculated with this raw data, using statistical analysis. (source:


What we get then with HRV, is a measure of the influence and strength of your brake pedal. This means that the higher your HRV measurement, the stronger your PNS and thus the better your nervous system regulates stress. This means that you will be able to tolerate higher stress levels before you start to go into full gas pedal mode (SNS, also known as fight/flight) and that your recover faster when you have been under stress (whether emotional or physical).This is why elite athletes are now also using HRV to measure their resilience and to analyze how quickly their body restores after a training or competition day.


What influences your Heart Rate Variability

Now we know HRV is a measure of the variability of the time inbetween heartbeats, which is a product of how strong your PNS is. This means that when intervals are more variable, your brake pedal is more dominant and your HRV is stronger. Low variability indicates stress as a function of SNS activation, because to fuel the mobilization of energy needed for fight/flight, your heartbeat will start beating more steady. You can see this effect very easily when measuring HRV and doing a short sprint.


Note that there is always a balance between the PNS and SNS: they do not exclude one another, however one or the other is mostly dominant. Now let’s look at what influences your HRV.



As you might expect, stress is a major influence on your HRV level. We differentiate between acute and chronic stress. Acute stress is for example when we play sports, lift something heavy or make a sprint for the train. Acutes stress can help to increase your HRV when balanced with adequate rest and recovery.


In contrast, most of us often experience chronic stress which has a different impact on your HRV. When stress becomes chronic, for example during intense work days, the PNS is not activated often enough to restore our full vitality. Chronic stress may show up in measurements as a low HRV, often coupled with relatively high resting heart rate.



Inadequate sleep can have a strong influence on your HRV. You can notice this immediately during the morning after a night of less than ~6 hours of sleep. Your body and brain experience sleep deprivation as a severe stressor, which is reflected in a lowered HRV and other indicators like increased insulin resistance. Improving your sleep is therefore one of the primary starting points for optimizing your daily functioning.



Nutrition can also strongly influence your HRV. The type of effects can be very wide ranged and complex, which is too much to cover in this article. However keep in mind that if you start measuring HRV, your diet can have a strong impact on your results. This is one of the reasons to measure your baseline first thing in the morning, before having breakfast.



Any form of illness, infection or inflammation can impact your HRV. Again, the interactions can be complex, but generally being in a state of sickness or inflammation will be coupled with a lower vagal tone and high SNS activation. This may be temporary and give a abnormal HRV reading compared to your baseline, which you may return relatively quickly to after the illness has cleared. However, chronic illness can shift your HRV permanently and lowered HRV has been linked to several (chronic) diseases, for example:

  • Heart disease
  • Cancer
  • Chronic lower respiratory diseases
  • Stroke (cerebrovascular diseases)
  • Alzheimer’s disease
  • Diabetes



A lesser known influence on vagal tone is trauma. The impact of trauma however can be quite enormous. Depending on the type and amount of trauma a person has in his or her history, vagal tone will be lowered, sometimes severely. Trauma is where the interactions between the PNS and SNS can become quite complex and is beyond our scope for now. But since trauma has such an important effect on HRV, keep this one in mind as a potentially important piece into increasing your resilience and overall well-being.


Positive impacts

Of course, there are many things that can positively impact HRV as well. Most of them relate to resolving the items mentioned previously. Examples are mindfulness and yoga as stress management methods. Also, any intervention to sleep better will have a major impact on your HRV, which I will spend more time on in a future article. Nutrition is important as it can also influence the amount of inflammation and illness in your body. Any diet that aims to reduce inflammation can indirectly improve your HRV (think of Paleo and Ketogenic type of diets). Depending on your individual needs, getting help in resolving past trauma(s) can also be a major piece in improving your HRV and resilience.


You can also actively train your HRV through stress and recovery training, for example with high-intensity interval training. Keep in mind however that this should be done when you’re not already stressed out from your daily routine. If you are, intense training can actually reduce your well-being further, since you’re just adding acute stress on top of the chronic stress. Sorting out your sleep quality and building in more rest into your day would be priorities in such a scenario, before looking into doing (intense) physical training.


Finally, there are also specific exercises as a way to train your HRV and nervous system. An example are breathing exercises. By inhaling and exhaling for 5 seconds each, your HRV will improve instantly. This of course is a temporary effect, but it will become more permanent if you do breathing exercises more regularly. Also, adding to this gratitude or compassion visualizations can further enhance the effect on your HRV. You can find more about such practices in other articles on my blog or my new ebook.


How to measure your Heart Rate Variability

There are different ways to measure your HRV. There exist apps that use your smartphone camera to read your heartbeat from your finger. These are good for heart rate measurements, but too inaccurate for HRV measurements. Some smartwatches also offer the possibility to measure HRV, but experts disagree over whether the sensors in smartwatches are accurate enough.


One of the most reliable and cheapest ways to start measuring HRV is a heart rate monitor like the Polar H7, which is the one I use myself. The Polar H7 uses bluetooth to connect with your smartphone. You can then download an app of your choice to read the signal. My preferred app for this right now is ElitHRV. This app is free and gives you all the data you need. It also offers some more technical details if you like to get nerdy. Below are some screenshots of what this app looks like.

This is the result of a morning reading of my HRV after being restored fully from a good night sleep and (passive) recovery from physical training. According to EliteHRV's algorithm I score a 10 out of 10, which means there is an optimal balance in the autonomic nervous system. Lower scores can be either on the left and right side, depending if you're sympathetically or parasympathetically dominant.
This is the chart from one of my morning readings. You can clearly see how my heart rate (red line) is quite variable, despite sitting on the couch for 5 minutes, doing nothing. (heart rate is plotted on the right axis, HRV on the left). The purple line is the calculated HRV.
This is a screenshot of my HRV and heart rate during high intensity sprints. You can see that my heart beats very consistently during the sprints at a very high rate, with little variability.

The most important step in using HRV is starting to take daily measurements in the morning, preferably at the same time, sitting in the same position, for reliability. Then you can take short snapshots throughout the day to see how you do in specific situations. Notice the graphs where you can clearly see how my heart rate at rest varies from moment-to-moment. I’ve also added a graph from when I was doing sprints at 100% effort, just to show you what sympathetic activation looks like.


The ElitHRV app gives you a daily readiness score based on your HRV. This is not equal to the ‘raw’ HRV measurement as they use an algorithm to calculate your baseline and subsequent scores. If you want to get technical, you can check out this article on the EliteHRV website about what the technical data means and how your hold up against your demographic.



You now know the essentials of what Heart Rate Variability is and how it can help you get insight into your resilience. Having a high HRV translates to better functioning of your autonomic nervous system and increased capacity to deal with stress. Low HRV indicates that you’re experiencing high stress levels and might need (more) time to recover fully.


Also keep in mind that HRV is highly impacted by several factors like accumulated stress, sleep, nutrition, sickness and trauma. Your HRV changes along with your moment-to-moment physiological state. For example changing your breathing rhythm can instantly shift your HRV, which is good for training your autonomic nervous system, but makes the reading of your ‘natural’ HRV in the moment unreliable.


Although HRV readings might not always be easily attributed to single causes, it definitely gives a very integrated measure of the state of your organism.


Are you considering to start measuring your HRV? Share your questions, ideas and experiences in the comments!

11 april 2017

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