Heart Rate Variability (HRV): It’s More Important Than You Thought!

You may already know that your heart rate is an indicator of your level of fitness, and that the lower your resting heart rate, the higher your fitness. What is less commonly known is how your heart rate is connected to everything happening in your body and, more generally, your life. 

What is HRV? 

Heart Rate Variability measures the variation in time between heartbeats in seconds and milliseconds. Your doctor, when examining your heart, may take 15 seconds to count your heart’s beats. They will then extrapolate how many times your heart beats per minute to arrive at, say, an average of 60 beats per minute. While this is a helpful gauge of your heart health, it’s very likely that your heart is not beating exactly every second. HRV looks at the variability between heart beats in milliseconds and gives a more holistic picture of your body’s functioning and your health more generally. 

HRV is a great standard to measure how your body handles all types of stress, including physical, mental, and emotional. And while, generally, you don’t want a higher resting heart rate, you do want higher HRV. 

HRV and the Autonomic Nervous System

Your heart rate’s variability is a result of two competing branches of your Autonomic Nervous System: your Parasympathetic Nervous System (PNS) and your Sympathetic Nervous System (SNS). 

• The Parasympathetic Nervous System is the ‘rest and digest’ system, which lowers your heart rate in times of relaxation and recovery, conserves energy, and slows the heart rate. It is also largely out of our conscious control, and is in charge of regulating our breathing, heart rate, and body temperature. 

• The Sympathetic Nervous System is the ‘activating’ system, and responds to external stressors by slowing down all ‘inessential’ body systems (which can include our reproductive organs, hair and nail growth, food digestion and more) and elevating our heart rate.

So, your HRV paints a picture of the balance between these two systems. As mentioned above, higher HRV is ideal as it shows that your nervous system is responsive to a wide variety of stimuli. And when your body and nervous system are relaxed, there tends to be greater variability. 

So, you might be thinking: “Sounds like I should always be relaxing”. Yes and no! 

Optimize Exercise to Change your HRV

We do need some measure of stress in our lives for optimal HRV. Exercise, for one, is a stressor that we know improves our health. Highly-trained athletes stress their bodies and their hearts often in order to improve their HRV and thus their performance. They spend more time at their max heart rate, as compared to a non-exercising person. But, as experts state, it’s not the max heart rate that tells the whole story–what matters is that balance is restored once you’re out of the ‘red zone’. They may ask: how long can you comfortably maintain a high heart rate? And how quickly can your body return to its resting state or ‘green zone’?

A sign of excellent HRV is that you are capable of doing more in this max heart rate zone than most people. Many exercisers, when just starting on their fitness journey, will describe feeling ‘out of control’ and ‘dying’ when the heart rate is elevated. As their fitness improves, however, they’ll find that they can do more, go harder and faster than they could previously while in their ‘red zone’. 

So, make sure that you are regularly challenging yourself in your workouts. How hard are you working, really? The RPE scale can be a useful metric for judging your effort (you can learn more about it at this article here). And remember: you don’t have to kill yourself! It’s not necessary to stay in the red zone for more than thirty seconds or a minute at a time.

The recovery after your workout is just as essential. It doesn’t matter how hard you go, and how high your heart rate–if you’re not recovering, it’s all for nought. It’s okay to feel run down the next day after a particularly challenging workout; prioritize your rest and you will see the benefits in your HRV. To learn how to recover constructively, read our article here! 

Don’t be surprised when your resting heart rate lowers as well. As you grow fitter, your heart will become stronger, so each beat has more ‘stroke volume’. Your body becomes more efficient, so it is capable of doing more with fewer heart beats. A lower heart rate means you have more room for deviation between your lowest and highest heart rate–increasing your HRV. All good news!

What Else Affects HRV?

There are many, many factors that affect our HRV; in fact, HRV is one of the most sensitive body metrics out there.

Age and sex are two factors that are typically out of our control. Women will generally have a lower HRV than men, though the difference seems to level out after the age of 50. HRV tends to also decline as we age, though studies have shown that even that can be controlled, and healthy, exercising individuals can maintain HRV even as they get older. 

Hydration levels, fatigue, alcohol, smoking, the amount and type of food you just ate, the quality of the sleep you had the night before–these will all have a say in your HRV. If you have a food intolerance, this will have a greater drag on your system and your HRV. This is why it’s essential to learn how to sift through the noise to get the most accurate and salient information. 

Remember, our body is always competing for resources; so if you’re putting many demands  on your body, your heart will have to work extra hard. When we’re stressed, our HRV will lower, and there will be fewer resources to allocate to take care of all of our body’s many functions. 

How to Measure your HRV

Unfortunately, medical devices that measure HRV, such an ECG, are not very accessible. This is where fitness trackers can come into play: if you’re serious about keeping track of your HRV, I would recommend investing in a good wearable device. These will track your HRV trends, which will give you more usable information than just tracking once, such as when you’re visiting your doctor or when you remember to do it. You can find our article on the best wearable fitness devices here! 

If you don’t have access to a device, measuring your heart rate immediately after waking up, and before you get out of bed, is the best way to take your resting heart rate. And while you’re working out, especially after an all-out effort, take 15 seconds to take your heart rate. 

Finding one’s max heart rate is an imprecise science, and there are a couple of calculations that you can use:

[ 220 – Age ]: the most common and widely used maximum heart rate formula

[ 207 – 0.7 x Age ]: a more precise formula, adjusted for people over the age of 40

[ 211 – 0.64 x Age ]: a slightly more precise formula, adjusted for generally active people

No matter which calculation you use, Remember, the information gained from tracking your HRV is only meaningful if you’re measuring day after day. Everyone will have good days and bad days, days when you’re dehydrated or when you don’t sleep well, but it’s the trends that matter and that paint the most comprehensive picture.

We hope you enjoyed this article! 

Wishing you all the best on your journey to optimum health!

Written by Theresa Faulder, Master’s in English, Certified Personal Trainer and Infofit fitness blog writer.