You probably aren’t following this important heart health statistic

This story is part of Health in numbersCNET’s deep dive into how we quantify health.

When we think of keep track of our health statisticsthe first one that comes to mind is our heartbeat† Yes, it is very important to keep an eye on, but there is another important health indicator that you have probably never heard of. Enter heart rate variability or HRV. It can tell you about your health, stress, fitness and much more.

Your HRV is the amount of time between your heartbeats. And while that may not sound in-depth, it’s actually an important statistic if you know how to find it. Unlike heart rate or heart rate, it is a bit more difficult to measure.

One of the few wearables that measures HRV, the Whoop tracker, uses these and several other metrics to help you determine if you’ve recovered well enough from your last workout to train again. These detailed statistics are one of the reasons why professional athletes and endurance trainers are huge fans of the product. In fact, I had never really heard of HRV until I checked out the Whoop band on the company site.

Just like any other statistic that fitness trackers HRV is a bit useless unless you understand what it means and how you can use it to improve your health and fitness. Keep reading to learn more about what HRV is, how to measure it and how it can help you optimize your health.

What is heart rate variability?

“HRV is the amount of time between each heartbeat, which is controlled by the autonomic nervous system,” Holly Roser, certified personal trainer, told CNET. The autonomic nervous system is basically your body’s stress or nervous system regulator and contains two major parts: parasympathetic and sympathetic.

Person in workout clothes checking their watch

HRV is controlled by your nervous system, which regulates many important systems in your body.

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The nervous system is so important because it controls involuntary systems in your body, such as heart rate, digestion, and blood pressure, among others. You can think of the sympathetic nervous system response as your stress response, or what kicks you into “fight or flight” mode. The response of the parasympathetic nervous system is known as the “resting and digesting state” and is important in helping your body digest food and lowering your heart rate and blood pressure.

You probably know that lowering stress is important for health, but what does this have to do with fitness? A lot.

Ever since recovery Being such an important part of your overall fitness routine, HRV is one of the most useful metrics for telling you if your body has recovered (i.e. not in a stressed or sympathetic state) so you can get back to training.

For example, maybe you’ve been working out a lot and not sleeping much – but you always stick to your 6 a.m. workout no matter what. You can feel good technically, but you risk overtraining if you push yourself too much (especially without enough sleep). While using a sleep tracker is certainly useful for measuring how well you have slept, HRV is another way of seeing how well you have actually recovered from a previous workout or even just from a stressful situation or a night out.

Measuring and using HRV

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The Whoop fitness tracker takes your HRV into account to show how well you have recovered from exercise.

Screenshot by Mercey Livingston/CNET

To measure HRV, you need some kind of heart rate monitor that can accurately measure patterns in your heart rate. Some of the most popular devices that include HRV tracking are the Whoop and the Apple Watch

Because HRV is quite complicated to measure accurately, it’s helpful if you use a device that also tracks your sleep, resting heart rate, and maximum heart rate, so you can get a bigger picture of your health.

For example, Whoop tracks your HRV, heart rate, exercise and sleep and uses an algorithm to suggest recovery or training. If your HRV is good (higher numbers are better), then you are in the optimal state to exercise or adapt to any kind of stress.

A good HRV is a sign that your nervous system can adapt well to different situations, which is good when it comes to coping with stress and balanced overall health. The average HRV varies by age, but it also varies by person — it’s best to follow your own patterns and notice any changes over time, rather than comparing yourself to others.

Why HRV is important for fitness and overall health

“If your HRV is high, it could be an indication that you’re living a healthier lifestyle and that you’ve been following healthy habits, such as getting a good night’s sleep, exercising regularly, staying hydrated, eating a healthy diet and reducing stress,” Roser said.

Since your HRV pattern is a reflection of the amount of stress your body is experiencing, virtually all facets of your lifestyle can affect it. Remember that stress is more than mental — things like illness, emotional hardship, lack of sleep, and dehydration are all examples of things that put stress on your body.

Everyone experiences some level of stress (and some types of stress, such as exercise, can be helpful), but it’s important to understand how well your body handles it. If not, you risk overtraining or straining your body when it’s best to take a break. And this can quickly lead to burnout, getting sick, or just plain exhausted.

“When things are ideal, your beat-to-beat timing is very variable. If your interval timing between heartbeats is the same, you haven’t recovered yet. That suggests you might be overtrained, or you just aren’t yet recovered and need either a lighter recovery day or a rest day to achieve a more optimal fitness,” said Debra Atkinson, MS, CSCS.

Who can benefit from HRV tracking?

Although HRV is more popular in the world of professional sports and endurance training, it can be beneficial for everyone to keep track. Even if you don’t exercise much or exercise professionally, HRV can help you get a better picture of your body’s stress level, as well as recovery and fitness levels. If you’re the type to be prone to burnout or overtraining, HRV tracking can be a useful tool to make sure your rest days and recovery are a priority.

“For individuals who have a tendency to persevere and work hard to get better results, HRV monitoring can provide concrete evidence of much-needed rest. If you are probably not resting yourself, but find yourself frequently injured or ill HRV can provide the evidence you need to pull back and recover sufficiently so that your fitness, immune system and overall stress level are all more optimal,” Atkinson said.

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The information in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified healthcare professional if you have any questions about a medical condition or health goals.

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