A lot has changed in the last few years. You can measure and track about every metric you can think of… calories, number of steps, weight, sleep, heart rate and blood pressure are just a few examples. Heart rate variability – or HRV in short- is a fascinating metric which is gaining increasing traction. A number of wearables, like the Oura ring, Whoop and the Apple Watch measure it. But what is HRV and can it help you live better for longer? Let’s explore some of the fundamentals around this variable.

What is heart rate variability?

Heart rate variability is not the same as heart beats. Simply put, it’s the variation in time between each of your heart beats, measured in milliseconds.

If your heart beats at a rate of 60 beats per minute, this doesn’t mean there is a beat every second. There may be 0.8 seconds between two beats, whilst there could be 1.1 seconds between two others. This variation is what heart rate variability is. The greater the variability, the higher is your body’s “readiness” to perform. HRV measures your ability to cope with “stressors”. It’s a measure of resilience and wellbeing.

What does HRV have to do with your nervous system?

HRV is closely linked to what’s called the autonomic nervous system, and the balance between its two branches: the sympathetic and parasympathetic systems.

The sympathetic system reacts to things like stress and exercise and increases your heart rate – it’s also called the fight or flight response. Whilst the parasympathetic branch – also called the rest and digest system – stimulates digestion, helps the body relax and slows the heart rate.  

The signals the two branches of the nervous system simultaneously send to the heart, make your heart rate constantly fluctuate, and this is what determines your heart variability.

By balancing its two branches, the autonomic nervous system helps you respond to everyday stress and regulate body functions like your breathing and heart rate.

Why is HRV important?

HRV is a non-invasive marker of the status of the nervous system. It reflects your ability to respond to different situation. If you’re stressed – meaning you’re more in a fight or flight mode – your heart speeds up limiting space for variability (low HRV). On the other hand, when you’re more in a relaxed state, your heart slows down, giving more room for variability to arise (high HRV).

A high HRV indicates that your body is responsive to stimuli from both the sympathetic and the parasympathetic systems. It’s a sign that your nervous system is balanced, and you’re ready to perform at your best. High HRV is linked to good fitness and recovery.

A low HRV suggests that the balance is shifted towards one branch of the nervous system, which is more dominating than the other. A low HRV could be a sign of stress (physical or mental), illness, tiredness, overtraining or dehydration.

Which factors affect HRV?

A number of factors can affect your HRV. These include:

• Stress
• Diet
• Alcohol
• Sleep
• Exercise volume and intensity
• Rest and recovery after workouts
• Age
• Genetics

What is a good HRV?

There’s no straight answer to this question! HRV varies throughout the day, from day to day and between different people. It’s a highly individual measurement. As already mentioned, there are a number of elements which influence this metric. And as no two people are the same, there’s no point comparing yourself to someone else! 

A number of wearables and apps, like the apple watch, Oura ring, Polar chest strap and Welltory app can track your HRV. These usually establish your baseline after measurements for a few days or weeks. Deviation from your baseline will give an indication as to whether your HRV at the time of measurement is high (your body is rested and ready for activity) or low (your body is stressed and needs recovery).

HRV and longevity

There’s possibly a link between high HRV and a long lifespan. A high HRV is linked to reduced mortality and enhanced wellbeing and quality of life. A study in The American Journal of Cardiology has also shown that high HRV values in the elderly are a good marker to predict longevity. In contrast, other studies show that a low HRV is not only linked to worsening depression and anxiety, but also to a higher risk of death and cardiovascular disease.

How can I improve HRV?

The good news is that there are plenty of things you can do to improve your HRV. These include:

• Regular exercise
• A healthy balance diet
• Avoiding alcohol
• Sleeping well
• Breathing exercises (this is a whole subject in itself!) 

In essence…

HRV is not only a great measure for fitness, but it can also give you insight into your health, readiness and recovery. The good thing is: it’s a variable! So you can do plenty of things to give it a boost and hopefully extend your healthspan and longevity on the way.