Heart Rate Variability (HRV)

Heart Rate Variability (HRV)

This is a phrase you may have heard of in the past couple of years. This is largely due to the massive increase in wearable fitness trackers. Some of these trackers now include heart rate variability (HRV) as one of the markers they monitor. So why is this and why is following your heart rate variability so important.


Well first of all lets look at what is heart rate variability?


Heart rate variability or HRV is the variation in the time interval between consecutive heartbeats in milliseconds. A normal, healthy heart does not tick evenly like a metronome, but instead, when looking at the milliseconds between heartbeats, there is constant variation. In general, we are not acutely aware of this variation; it’s not the same as the heart rate (beats per minute) increasing and decreasing as we go about our daily business. Here’s a tip for anyone who wants to experience it: place a finger gently on your neck or wrist and find your pulse. You should feel that the longest intervals take place when you exhale, and the shortest intervals when you inhale. In addition to respiration, HRV is influenced acutely by exercise, hormonal reactions, metabolic processes, cognitive processes, stress and recovery.


So now you have an idea what your HRV is. Lets look at why its important to track it.


Your HRV can be monitored in several ways from a Electrocardiogram (ECG) in a hospital to a fitness tracker such as the Oura ring. The latter is one of the most comprehensive and popular fitness trackers to date. It obviously doesn't give the exact same data as a £2000 ECG machine however for the price (£250) it gives you a clear indication of your HRV amongst other things.


The Oura ring measures HRV in a 5 minute timeframe. By doing this over a 24 hour period it can assess your HRV pattern which you can then view on an App on your mobile phone.

To summarise if the intervals between your heartbeats are rather constant then your HRV is LOW and if the intervals between your heartbeats are varying then your HRV is HIGH.


To understand what the definitions of HIGH and LOW HRV are then you need to have a brief understanding of our autonomic nervous system (ANS).


The ANS is part of the nervous system that controls and regulates the internal organs such as the heart, respiration rate and digestion without any conscious recognition.


The autonomic nervous system comprises two antagonistic sets of nerves, the sympathetic and parasympathetic nervous systems. The sympathetic nervous system connects the internal organs to the brain by spinal nerves. When stimulated, these nerves prepare the body for stress by increasing the heart rate, increasing blood flow to the muscles, and decreasing blood flow to the skin. This is commonly known as your ‘fight or flight’ system. The opposite of this are the nerve fibres of the parasympathetic nervous system. This is primarily the vagus nerve and lumbar spinal nerves. When stimulated, these nerves increase digestive secretions and reduce the heartbeat.


Which when summarised means when at rest we are in a parasympathetic state and when ready for action were in a sympathetic state. As you can see from the illustration below we are in a state of readiness when in a sympathetic state. This is obviously an advantage when its required however 

for perfect health we need to be in a parasympathetic state more than not.


Hence why tracking your HRV can give you an indication of your overall health and general fitness.

With the aim being to lower our heart rate and increase our HRV.


Now your HRV is unique to you as it is affected by a number of internal and external factors such your age your hormones overall body functions including our fitness, food and nutrition and lifestyle.


As such you should not compare your HRV with others. Instead track your own over a period of time and see which things actually increase your HRV. It is generally accepted that your HRV is generally higher when you are fit and healthy.


So how can you learn from tracking your HRV?


Tracking your HRV is just an indication of your overall health and fitness and should be used in conjunction with other data such as blood pressure etc. By tracking it over a period of time you can assess what your baseline HRV is. The Oura ring over time will show you this. Once this is known you can then assess what lifestyle changes raise or even lower your HRV.


For example if your HRV is low this maybe an indication that your body is under stress such as an oncoming infection or your just tired and aching from too much training.

I find with my tracker that my HRV will lower along with a large increase in my sleeping heart rate when Im coming down with a cold or chest infection. Whats interesting is that you will get this reading before you actually start the feel the symptoms of the infection. So from that point of view you can take some remedial action before the infection really kicks in.


If you do invest in a tracker you will notice that your HRV drops after intense exercise. However if you recover well your HRV will soon jump back up again. If it remains low it is a good indication that your body hasn't fully recovered from that training session.


So as you can see having an understanding of your HRV can help you have an understanding of how your body works and help you live a long healthy life


We are not endorsing any particular fitness trackers or affiliated with them in any way. I just mention the Oura ring as its the one I use and can speak about it personally.


Happy Tracking!