Heart Rate Variablility (HRV) 101

Heart Rate Variablility (HRV) 101

What is Heart Rate Variability and how can tracking it improve your performance and recovery?

Other than collagen, there’s another buzzword doing the rounds in the sport and fitness community at the moment and that is ‘Heart Rate Variability’ or HRV for short.

What is Heart Rate Variability (HRV)?

Heart Rate Variability (HRV) is quite simply the variance in time between the individual beats of your heart and can actually be one of the most objective measures of how your body is performing AND recovering.


We have been measuring heart rate in sports and activities for over 50 years ever since the very first portable heart rate monitor was created and having this data available has already revolutionised the way we train and recover.

So why fix what isn’t broken? Why do we need to measure HRV? Surely when our heart rate is 60 beats per minute (bpm) it’s beating once a second, right? Wrong.

What a lot of people don’t realise is that your heart rate isn’t as regular or as metronomic as we thought. Before you get worried, your heart will still be beating 60 times in that minute but often there is very small variation between heart beats. So small, that normal heart rate monitors just can’t measure it!

For example, between 2 beats there may have been a 0.8 second gap and maybe even 1.2 seconds between another. But the overall beats per minute was still 60. As a general rule of thumb, the greater the variability, the better prepared your body is to perform at optimal levels. And vice versa. We’ll explain exactly why this is so a little later on.


Whilst HRV is measured from the actual function of our heart and can be measured using specialist devices, it is actually a measure of the activity of your autonomic nervous system which manifests itself in our heart beat.

There it is again… autonomic nervous system. If you’re not sure what that is, don’t worry. Not many people do and our understanding of it continues to grow all the time.

Your autonomic nervous system is the part of your nervous system that controls everything about your physiology that is involuntary; essentially all the body systems that we don’t have direct control over.

To make things even more complicated, the autonomic nervous system is made up of two parts: the parasympathetic nervous system which is associated with being at ‘rest’ and decreases your heart rate.  

And the second being the sympathetic nervous system which is associated with being ‘active’ and increases your heart rate in response to external stimuli like exercise and stress.

The variability in the beats of your heart comes from these two branches functioning at the same time, effectively competing for the body’s resources and in doing so sending two different signals to your heart. You with us so far?

A balanced nervous system is simultaneously telling your heart to both slow down and speed up by your parasympathetic and sympathetic systems respectively and creates the variability in the beating of our heart that we call our HRV. Well that wasn’t so hard, was it!


How can HRV tracking help me in my training?

But that’s not the end of the story. Now we know what it is, we can dive a little deeper into exactly why HRV is a sign of fitness AND fatigue; the most important aspects to consider when living an active lifestyle.

When your HRV is high, your body is switching on and off signals from both branches of the autonomic nervous system with ease. Able to quickly divert key resources and energy to important tasks like digestion and exercise faster than a click of a finger. Making you a highly functional and crucially adaptable performer in all aspects of your life; not just intense physical exercise.

It could be recovering after that workout, socialising with friends, practicing meditation or an important presentation at work. All of these are stressors and demand energy and resources from the body, and if you are running optimally you can perform each of these to the best of your ability and reap the rewards.

But it’s not all butterflies and rainbows. On the other hand, if your HRV is low this means that one branch of the autonomic nervous system is shouting louder than the other. It is usually the sympathetic nervous system as this responds very strongly to intense stimuli like physical exercise, stress and sleep deprivation.

In certain situations this is a good thing. If we are running a race, we want our sympathetic activity to be high (and therefore HRV to be suppressed) as we demand focus and attention from the body on delivering blood, oxygen and carbohydrates to our muscles.

If you’re not so active, low HRV is a great indicator that your body is stressed and working hard for another reason. Think fatigue, stress, illness, dehydration and even injury – all of these can be spotted through downward trends in your HRV relative to the amount of activity you are doing or not doing.


What is a good HRV?

We’re competitive folk at the end of the day so naturally we want to find out how high we can go but… and yes there is a but. Just like our heart rate, your heart rate variability is entirely unique to you. The magic ‘high’ HRV that we think we should all aim for simply does not exist.

We all have our own highs, lows, averages and baseline range and being able to track this consistently and accurately over time will offer you a physical and mental advantage like no other.

Your heart rate variability is also determined by your age, training volume and intensity, even genetics and other health conditions and can fluctuate daily. That’s why looking at long term trends of your HRV is what really matters.

Getting a reading one day and doing nothing with it is almost a case of data for data’s sake which is why technology and software are being developed together to help you understand the science and reasoning behind your HRV on a daily basis.

All of this together will help you take into account the effect of training, sleep, recovery and even your daily routines, behaviours and diet too. Simply drinking water can increase your HRV in the short term.

Because HRV does fluctuate so much, measuring and visualising that measurement 24/7 is incredibly messy and would take an analytics expert to sort through and understand it.

This is why an aggregate measurement is taken whilst you are in deep sleep; a time when your body is least distracted by other stimuli and can therefore give an accurate and objective reflection of how your body is doing. The device and software will then present that data to you in the morning for you to asses and track your daily trends.

How can I improve my HRV?

A few simple methods for improving your HRV:

Hydration – being well hydrated throughout the day helps your body pump blood around your body more easily which leads to improvements in HRV.

Healthy Balanced Diet – the food we eat and the times at which we eat it play a massive role in how our body performs and recovers.

Train Smart – constantly pushing to your absolute limits in training is a sure fire way to overwork your body and lead to massive decreases in your HRV and consequently increases your resting heart rate which is another important metric of physiological condition and readiness.


As technology advances more and more, our ability to measure important metrics like HRV is becoming more and more accessible to you and me; where it might previously have been reserved for only the best athletes in the world and as a result it is already revolutionising (again) our understanding of human performance and thus, the way we train and recover.

Bringing HRV tracking into the hands of everyday athletes and consumers is the talk of the fitness wearables community right now and US based company Whoop is certainly leading the charge; with leading smartwatch companies like Garmin, Polar and even Apple left to play catch up.

So if you’re like us and love the science and data behind human performance and constantly look for that extra 1 percent, then maybe HRV guided training is just what you are looking for.


We hope you enjoyed reading this article? Do you use HRV in your training? Will you consider doing so after reading this? Let us know in the comments section down below. Don’t forget to share this with someone who you know would benefit from reading this. The U Perform family loves sharing ideas and encouraging each other.