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What is Heart Rate Variability (HRV) and why is it important?

What is Heart Rate Variability (HRV) and why is it important?

How easily do you cope with challenges and stress in your life?
No, in fact, don’t tell me. I can actually predict your answer.

Well, I can predict your answer if I could take one specific and easy measurement from your body.


Your ‘adaptive reserves’

Your in-the-moment ability to handle physical, emotional and mental stress is also called your “adaptive reserves”.

We could say that sleep, physical activity and a nutritious diet build up these adaptive reserves. And that, conversely, stress depletes these.


Easy to measure

It also turns out that there is a simple way to measure your adaptive reserves throughout the day. You can do this by observing a simple metric: your “Heart Rate Variability” (HRV).

It’s not that difficult to do. It can actually be measured in less than a minute, with an inexpensive chest strap or finger sensor, and a simple smart phone app.


What is Heart Rate Variability?

Your heart rate might be 60 beats per minute, or it might be 120 bpm. But what we’re talking about here is the interval between two heart beats.

And that interval might change from heartbeat to heartbeat.

A low HRV means that the interval is always the same.
A high HRV means that there is variation in the length of the interval.

Example: Let’s say your heart rate is 60 bpm. That means every second your heart produces a beat.

As an example, a high HRV could mean intervals like this:

1.05 sec
0.97 sec
1.02 sec
0.99 sec


Or look at this picture to get the idea:

What is Heart Rate Variability?
Variation of beat to beat intervals, in milliseconds. (845 ms = 0.845 second)


Why is HRV important?

A low HRV is a sign of the sympathetic autonomic nervous system (also called the “fight-or-flight” system, or the stress system).

And a higher HRV is associated with the parasympathetic nervous system (or the relaxed state).


Our autonomic nervous system has two components: the sympathetic nervous system and the parasympathetic nervous system. These two take turns in running the show.

When we’re relaxed, or engaged in restful activities like eating and digesting, it’s because our parasympathetic nervous system is active (the “rest-and-digest” response).

On the other hand, it is the sympathetic nervous system that is responsible for stimulating activities associated with the “fight-or-flight” response.


Sympathetic activities such as intense physical exercise, as well as periods of mental stress:

  • increase heart rate (HR)
  • and decrease our heart rate variability (HRV)

Parasympathetic activities (relaxing, doing yoga, meditating), in contrast:

  • decrease heart rate
  • increase heart rate variability


Creating balance

Of course the trick is to have a good balance between the two nervous systems. A healthy person has a strong sympathetic AND parasympathetic system. Including the ability to shift between the two.

But the main weakness of people in our modern day society is a neglected parasympathetic system. There’s so much action going on and stress involved in our daily lives. In general, we’re too busy and don’t get enough rest.


A high variable heart rate is a sign of health

Heart rate variability is an important metric because, in general, a high variable heart rate is a sign of health.

It is a sign of the flexibility of the heart (as opposed to a rigidity) and of the capacity of the autonomic nervous system to adapt to changes in the demands we face every day.

“Heart rate variability turns out to be a generalized, deep measure of health. That’s because higher HRV is a strong indicator of resilience to stress, while low HRV is a sign of reduced capacity to tolerate stress. ”



Who uses Heart Rate Variability measurements?

Clinicians, academics, scientists and doctors

HRV is a marker for heart health, and health in general. There are tons of studies done by academics that prove this. In the last 10 years there have been more than 2000 studies that talk about HRV.

HRV can show changes in stress, even though other markers (such as blood pressure) are still in a normal range.



HRV measurements have been shown to be able to predict a likelihood of diseases occurring in the future (like diabetes or heart disease).

A high HRV has been linked to good health and fitness, while low HRV is linked to stress, fatigue and even burnout.

Although not widely used yet, the use of HRV measurements by doctors to predict illnesses is on the rise. Some believe that HRV measurements will become as common as taking a patient’s blood pressure or pulse.


The good thing is, you can learn to improve your HRV:


Heart Rate Variability biofeedback therapy

Originally, the use of HRV biofeedback therapy began in Russia, where it was applied to the treatment of asthma and many other conditions.

Research is now going on where HRV biofeedback is applied to various medical conditions, like:

  • anger
  • anxiety disorders
  • asthma
  • cardiovascular conditions
  • chronic obstructive pulmonary disorder
  • irritable bowel syndrome
  • chronic fatigue
  • chronic pain

By learning to control HRV, symptoms can be reduced.



Athletes can use HRV analysis in 2 ways:

  • to measure their overall fitness level (as shown by long-term changes in HRV)
  • to measure training load and overtraining (as shown by the short-term or daily changes in HRV)

To measure any signs of overtraining, athletes check their HRV first thing in the morning.

A drop in HRV (too much sympathetic activity) is linked to fatigue and overtraining. That’s when there’s a need to take time out to recover.

It’s easy to do with a chest strap and a smartphone app. A cheststrap like a Polar H7 works fine for this. And there are a few apps on the market, such as ithlete, Sweetwater or HRV4Training (for the latter you don’t even need a chest strap – you can just place your finger over the camera of the phone – as reliable as a chest strap).

Athletes can also use HRV biofeedback to cope with emotions, such as anxiety due to performance pressure. Here’s a study done on basketball players:

The effect of heart rate variability biofeedback on performance psychology of basketball players.

Personal use

You can also use HRV biofeedback to learn to get your HRV in the right ‘zone’. You don’t need to go to a professional for this, there are devices available on the market so you can do it yourself.

And, aside from fitness goals, you can also test activities yourself (with the same tools and apps mentioned before). You can do this before and after those activities. In this way you can see what has a positive effect on your HRV.


What increases HRV?

Read this post where Todd Becker of gettingstronger.org experiments with different activities that boost or decrease his HRV:

The Best Activity to Increase your Heart Rate Variability




3 Responses to What is Heart Rate Variability (HRV) and why is it important?

  1. Hi there, thanks, I like it:) am doing some of my own little experiments with it too. I noticed you wrote ‘And a higher HRV is associated with the sympathetic nervous system (or the relaxed state)’ under the point under ‘why is HRV important’. Must be a typo?

  2. Thanks for this introduction to HRV (heart rate variability). Well done. There are many apps now to measure and manage HRV on the market so it’s become very easy and inexpensive to look after your own HRV health.