This Is HRV: A Deep Dive Into The Most Important Metric For Health, Fitness, And Performance

Older man looking at a watch to check heart rate variability

Alright guys, grab your propeller hats because this is a deep dive article. Full warning, things are gonna get technical, but I promise you it will be worth it.  Today we’re going to talk about what may be the most important marker for health and fitness we can track: heart-rate variability. Heart-rate variability (HRV,) has become quite popular in the fitness world as a measurement of exercise recovery, but the implications go far, far beyond that. 

You see, heart-rate variability isn’t just a measurement of how well you have recovered between workouts. It is a direct reflection of the health of your nervous system. This marker can be used to predict and influence health risks, anxiety, burnout, and sleep quality. 

But what, exactly, is heart-rate variability? And how does it measure the health of our whole nervous system? There is much that goes into this, but at the surface level, HRV is a measurement of the variation of time intervals between heartbeats. You see, the heart is not a metronome. It is not intended to simply beat at an exact pace, and if it did, you would not be able to efficiently respond to stressors nor wind down and relax. 

While HRV cannot tell you everything, it is definitely one of the most widely-relevant markers of your well-being. However, the world of HRV measurements is complex and often confusing. Different devices offer different data, and there isn’t a widely accepted “norm” for HRV. 

This is why my aim is to give you a deep dive. It will get technical, and it will be long, but I believe the effort will be worth it. By going beneath the surface and creating a foundation, you will have more power to use this measurement than almost everyone else sporting a WHOOP wristband or Oura Ring. 

So strap in, buckle up, and get ready because this is HRV.


The Autonomic Nervous System

Picture of cells to represent the autonomic nervous systems role in heart rate variabilty.

To understand the incredible usefulness of HRV scores, we must understand the role of the autonomic nervous system.

Though the term “autonomic nervous system” may not mean anything to you, you actually know what it is. Ever heard the term “fight-or-flight?” Well, that’s one part of the autonomic nervous system. The autonomic nervous system is made up of the sympathetic nervous system and the parasympathetic nervous system. These systems are also known as the fight-or-flight response (sympathetic) and the rest and digest response (parasympathetic.)

The Sympathetic, Fight-or-Flight, System

The sympathetic nervous system creates a sympathetic response to the world around you. If you are faced with a threat, you need to turn off unnecessary functions and be ready to face, or flee, from danger. You can remember this by thinking of the literal meaning of the word “sympathetic.”

From the Latin “sympathia,” sympathetic means to react to an external feeling with a similar internal feeling. We most often think of this in terms of emotion, such as when sympathizing with a friend. We are feeling the same feeling that our friend does. In the case of the sympathetic nervous system, you are “sympathizing” with a stressful or potentially dangerous scenario in the world. You are responding to stress with stress, a heightened and alert state that is prepared to fight, flee, freeze, posture, or submit, depending on the scenario.

This system is often referred to as our stress response, and when the sympathetic nervous system becomes active, lower-order functions like digestion and reproduction become diminished, while organs involved with survival such as the heart, muscles, and brain, are bolstered. 

You may notice that all these parts are pretty useful during a workout. Yep, when you exercise, you are activating your sympathetic nervous system. This is a good thing. The sympathetic nervous system needs to be strong and ready. 

In terms of physical location, the sympathetic nervous system resides in the grey matter of our thoracic and lumbar spine. These cells directly influence our adrenal glands, which are responsible for releasing the neurotransmitters epinephrine and norepinephrine, aka adrenaline and nor-adrenaline. 

Basically, this system is in charge of rallying all the parts of our physiology most suited for physical action. 

The Parasympathetic, Rest & Digest, System

The parasympathetic system balances the sympathetic nervous system by promoting our calm, rested state. This is the state where we are most capable of healthy social interaction, proper digestive function, sexual arousal, and recovery. In essence, the parasympathetic system promotes activities that let us recharge. 

Physically, the vagus nerve is the primary component of our parasympathetic nervous system. The vagus nerve uses the neurotransmitter acetylcholine to slow down nerve firing. This nerve connects to many of our internal organs and can easily modulate their activity. 

Basically, the parasympathetic nervous system uses inhibitory neurotransmitters to calm or slow down our bodily processes. 

Gas Pedals & Brake Pads

One common misconception is that the autonomic nervous system acts as an “either/or” scenario; Either your sympathetic nervous system is on, or your parasympathetic nervous system is on. This isn’t exactly the case. In reality, these two symptoms act more like a car in drive. 

As we all know, if you put a car in drive and take your foot off the brake, the car will move forward. Even if you don’t have your foot on the gas, there is always some level of activity from the engine creating forward motion. This is how the sympathetic nervous system behaves; It is always turned on to some extent in case we need to deal with an emergency or threat. 

The parasympathetic nervous system is like the brakes in your car. Essentially, the pressure of the parasympathetic system overlays the pressure from the sympathetic nervous system to create a state of calm and stillness. 

The sympathetic nervous system has developed a bit of a reputation as the “bad guy” of our biology, but this is simply not the case. 

Good nervous system function is not about turning the sympathetic nervous system “off” any more than driving a car is about turning the engine off. You want your sympathetic nervous system to be strong and capable. You just also want it to be available when needed, and you want the “brake pads” of your parasympathetic nervous system to be healthy and able to slow down your sympathetic nervous system when it isn’t needed. 

The HRV Link

Here’s where HRV comes in. HRV values reflect the ability of your body to switch between parasympathetic dominance and sympathetic dominance as needed. Generally speaking, higher HRV values mean greater health and resilience of the whole Autonomic Nervous system.

This is where things get interesting: HRV has a bidirectional relationship with many things that improve our stress response. This means that things like high blood pressure or poor sleep will lower our HRV scores, but activities that improve HRV will also improve things like blood pressure and sleep quality. 

The reason this is so interesting is that we have known techniques for reliably improving HRV on a daily basis. 

Before we can do these things though, we need a way to track our HRV, and in the world of convoluted and inconsistent wearables and devices, it helps massively to understand just what exactly these tools are measuring. 


How HRV Is Measured

When it comes to the actual numbers HRV measuring devices will give you, there is no universal system. Companies can develop their own algorithms or scoring systems. However, most of these devices derive their scores from a few clinically metrics. The OURA ring and WHOOP wristband, for example, use a score called RMSSD, whereas hospital ECG devices often measure something called the SDNN.

These metrics are useful for different purposes, but if you don’t understand them, you can end up with unhelpful data. 

When it comes to how devices measure your HRV, they will either measure the electrical pattern of your heart or will use infrared light to detect changes in volume. 

ECG devices use electrodes placed on your chest to measure your heart rhythm. The advantage of these devices is that they can remove “artifact” beats that falsely increase HRV scores. These beats, such as heart palpitations, cause abnormally long gaps between heartbeats which results in higher HRV scores. However, high numbers of these beats usually mean dysfunction and your HRV is most-likely too low overall. 

PPG devices measure HRV via infrared light that is shined into your blood vessels to detect changes in blood volume. This is how the majority of devices measure HRV. Wrist straps, rings, ear clips, etc. all use PPG technology. 

Some PPG devices use algorithms to remove artifact beats from their data, but it is more difficult and these devices may be less accurate for 24 hours or other long measurements. 

Time Domain Vs. Frequency

In terms of metrics, the two most fundamental ways of measuring HRV are time-domain measurements and frequency-band measurements. 

Time-domain Measurements 

Time-domain measurements track your HRV by finding an average. A device will measure the amount of time in milliseconds between your heartbeats, and then determine the average variance of those times. 

For example, if 2 of my heartbeats are 800 milliseconds apart, then the next beat comes 750 milliseconds after, I have an average HRV of 50 milliseconds. 

Simply measuring HRV from only a few heartbeats is not very useful, and different types of time-domain measurements require 5 minutes up to 24 hours for optimal HRV measurements. 

When it comes to wearable devices, RMSSD measurements are the most common and useful form of time-domain measurement. This is because of two factors. 

For one thing, RMSSD measurements can provide useful data with as little as 10 seconds of measurement (though 5 minutes is optimal,) and RMSSD measurements ignore the effect of respiration on HRV. What this means is that RMSSD measurements are better for understanding your general recovery level independent from activities like conscious breathing or meditation. 

This makes RMSSD measurements particularly useful for tracking sleep quality, determining readiness to exercise, and understanding the strength of your parasympathetic nervous system. 

The second major time-domain measurement is called SDNN. SDNN measurements track HRV between normal heartbeats while excluding artifact beats like heart palpitations and arrhythmia. 

SDNN measurements require at least 5 minutes but are not considered clinically relevant unless tracked for 24 hours. Because of this, SDNN measurements typically come from more invasive ECG equipment like Holter monitors and chest straps. 

In general, you won’t find good devices that use SDNN unless they are ECG chest straps, and even if you do use such a device, we need to remember the data isn’t valuable unless we measure for 24 hours. 

With that in mind, 24-hour SDNN is considered the gold standard for cardiac health and can be very useful information to have. 

24-hour SDNN measurements of less than 50 milliseconds (less than 50 ms average variance between heartbeats) are associated with being unhealthy, 50 to 100 is associated with compromised health, and values greater than 100 are considered healthy. 

In heart attack survivors, those with an SDNN over 100ms are 5 times more likely to survive over the course of a 31 month period than those with an SDNN less than 50. 

Basically, stick with RMSSD when using PPG devices (wrist straps, rings.) If you have access to an ECG device (chest straps or electrode-based devices) you can measure SDNN but it’s most useful with a 24-hour measurement. 

Frequency

The other major classification for HRV measurements is frequency. As opposed to time-domain, which creates a score from the average time between beats, frequency measurements categorize based on the wave structure of our heart rhythm.

Ever heard of brain-waves? It’s the same thing, just for your heart. Neural activity can be classified into brain wave frequencies that all mean different things. The lowest frequency brainwaves are called Delta waves and are associated with sleep, and then higher frequency waves are associated with higher brain activity functions.

With HRV, we have ultra-low, very-low, low, and high-frequency waves. In my opinion, frequency measurements are more confusing than time-domain measurements, but they have been getting much more popular in recent years and they do offer unique information. 

With HRV, frequency measurements are kind-of like shining a light through a prism. As the light passes through the prism, it is split into its multiple wavelengths.

Well, HRV can be split into component wavelengths as well, so-to-speak. For any given HRV measurement, there will be heart-activity waves in the ultra-low frequency band, very-low-frequency band, low-frequency band, and/or high-frequency band. 

The idea is to determine which of these frequency bands is dominant over the course of a given HRV measurement, though multiple bands may be present. Just like the brain produces more than one kind of brainwave at a time, your heart can produce multiple HRV waves. 

Here is a brief description of each frequency band and how to use the info. 

Ultra-Low-Frequency Band: .003hz. Only detectable on a 24-hour measurement. Indicates very slow biology processes. Not much is known about this band currently, but it is guessed to be involved with circadian biology. 

Very-Low-Frequency Band: .003hz to .04hz. Can be detected with 5 minutes of data but 24 hours is the gold standard. Low power levels of this frequency are the most predictive of poor health outcomes. This is associated with high inflammation, low testosterone, and rhythmic death. This frequency band is the most relevant clinically at this time. It is likely that parasympathetic activity promotes the power of this band. 

Low-Frequency Band: .04hz to .15hz. Can be detected in 2 minutes. This band is the most commonly recorded by phone HRV measurements. High power in this band may represent autonomic balance, and breathing exercises are known to increase the power of this band. Coherence and resonance training programs, methods for improving HRV, are mostly concerned with increasing the strength of your low-frequency waves. 

High-Frequency Band: .15hz to .40hz. Can be detected in one minute. High-frequency band strength is associated with anxiety and panic. The power of this band can be lowered with breathing techniques. 

Low-Frequency to High-Frequency Ratio: Lastly, one of the ways we can measure our autonomic nervous system balance is by looking at the ratio of low-frequency to high-frequency band strength. By comparing these two figures, we can see if our parasympathetic nervous system is dominant, or our sympathetic, fight-or-flight system is dominant. Low ratios mean parasympathetic dominance and you should feel calm at these times. High ratios mean sympathetic dominance and you may feel edgy. This is best calculated for over 24 hours.

So if you use a fancy app like nature beat or EliteHRV and you see Frequency band scores, now you know what they mean. Different devices may use different systems, but seeing which brand is most powerful can give you insight. 

Whoo! Give yourself a pat on the back! You’ve survived the technical jargon. Now we can finally get into devices, and how to use HRV to improve your life!


Wristbands, Rings, Chest-Straps, Oh My!

Guy with a smartwatch measuring heart rate variability.

So, we’ve survived HRV science and now we’re ready to measure. You now know what it means if your HRV device tells you you have a high frequency or low-frequency HRV, as well as how long you should measure depending on if your device uses SDNN or RMSSD. 

Once we have our scores, what do they mean? Well, regardless of the scores you get, there is one simple rule you can remember to always make use of them:

You are your baseline. 

We’ve talked in detail about what HRV scores mean, but when it comes to actually using them, it is far more important to develop your own personal baseline than to compare yourself with the general population. 

You see, many people begin tracking their HRV and start asking “is this a good score?” the very same day. Depending on your age, weight, diet, etc. your HRV scores will vary greatly compared to other people. 

It is far better to compare yourself to who you were yesterday than to who others are today. We’ll get into this more in the next section, but it’s good to know before we start talking gear. 

Most of the devices I recommend using measure RMSSD because it is useful with as little as 5 minutes of analysis. Some devices measure in SDNN anyway, but unless you are taking a full 24-hour measurement, stick with RMSSD. 

The following list contains popular HRV devices and lists what they measure. Mostly these devices give you your exact RMSSD score, but sometimes companies create their own algorithms that will turn this score into a number, say, between 0 and 100. This isn’t a bad thing, it just means you should be aware of the context of the device you’re using. 

Here are some of the best and most popular devices for measuring your HRV. 

Oura Ring

The Oura Ring is an HRV measuring ring that uses RMSSD to measure HRV. It gives you the exact RMSSD score in milliseconds. Oura rings are sold as a one time purchase for $300+ depending on the ring material you purchase. 

The Oura can be worn at almost all times, but I find it difficult to wear during workouts. I do not want it to get damaged or caught on something while I’m rock climbing or doing barbell work. Still, it’s easy enough to slip back on after, and many find this to be the least invasive quality HRV tracker. 

WHOOP Band

The WHOOP wristband also measures HRV using RMSSD. The WHOOP is purchasable through a subscription and is not available to buy as a one-time purchase. WHOOP provides its band for $30 a month, with a minimum of a $180 prepaid 6-month commitment. You can receive a discounted rate by prepaying for longer commitments. 

Like Oura, WHOOP shows you your exact RMSSD score. WHOOP also calculated custom figures it refers to as “strain” based on multiple markers, which can help to guide you if you forget all the technical info in this guide. 

Personally I really like WHOOP and I know Kelly and Juliet Starrett are fans, too. They tie your recovery data to a ton of useful tools, like daily questionnaires and fun reminders. Altogether WHOOP creates a very useful system for improving your recovery and creating positive lifestyle changes using your data. 

Apple Watch

Normally the apple watch measures HRV data in SDNN, which as we’ve discussed is best measured over the course of 24 hours with an ECG device (which the Apple Watch is not.) However, you can export your apple watch data in RMSSD by using the breath app on your apple watch.

This app automatically exports your HRV to the health app on your phone where it can be viewed in RMSSD. 

Though Apple doesn’t always have the most accurate features when it comes to self-quantification, using the breath app to track HRV has been validated. It has been shown to be just as accurate as chest strap ECG devices like the Polar H7.

The big disadvantage compared to something like the polar is the inability to export your data to a third-party app. The apple watch starts at $200. 

The Polar H7 Chest Strap

This is the first device on this list that analyzes ECG data rather than using PPG. Furthermore, this chest strap is $80 on Amazon, making it the least expensive HRV monitoring device so far. 

While the H7 does not come with a fancy app for measuring your HRV like the Oura or WHOOP, this is actually an advantage. Unlike the above devices, the polar can be directly paired with third-party apps to analyze your HRV. This means you can use it to get SDNN, RMSSD, or frequency data depending on the app you use. 

Many of these apps are far more extensive and offer great detail on all of your HRV scores. What’s more, is that the Polar H7 can accurately remove artifact heartbeats like arrhythmia and heart palpitations since it directly measures your heart’s electrical activity. 

In terms of data as well as expense, I recommend using the Polar H7 combined with Naturebeat, a clinical-grade HRV app co-developed by biohacker Ben Greenfield, to start measuring HRV. Another phenomenal app is EliteHRV. 

Basically, the Polar H7 gives those who want to nerd-out access to apps like Naturebeat where you can get tons of data such as frequency, SDNN, and RMSSD data, while also being more affordable than other devices on the market. 

It is more invasive and may not be ideal for consistent wear compared to an Oura ring or the WHOOP, but it’s really not that bad, and you can easily use it for a daily 5-minute baseline measurement or for the occasional 24-hour measurement. 

The Heartmath Institute Emwave or Inner Balance Device

The Heartmath Institute uses frequency measurements of HRV to train people to improve their personal scores. This group is heavily research-based, and their devices guide your breathing patterns to reach a state known as “resonance” where the power of your .1hz low-frequency band is strong. 

In the long run, this has been shown to improve HRV as well as many physical and mental health markers.

To use the device, you’ll attach a clip to your ear that monitors your heart rate variability, then the device will prompt you to inhale and exhale on cue. By following the prompts of the device, you will improve your HRV. 

These devices do not work for tracking HRV throughout the day, but you can still use them to develop a baseline. By doing your HRV training with these devices at the same time every day, such as in the morning immediately upon waking, you can see how your HRV is improving over time. 

I think these devices are phenomenal as a method for improving your HRV but fall short as tracking devices. Regardless, they are still powerful tools. Heartmath devices range from $120 to $200 depending on the device. 

Lief Therapeutics Chest Monitor

The Lief Therapeutics device is the Ku De Graw device for seriously using and improving your HRV. This device involves two electrodes that adhere to the left side of your chest and rib cage. 

Where the Lief excels beyond other devices is that it acts as a tracking device and an entrainment device. The Lief is meant to be worn through the day, and it will vibrate slightly when your HRV drops below your personal baseline. It then trains you to use breathing to increase your HRV. 

Because it measures electrically, the Lief system is particularly good at removing artifact beats. As far as price? You can get the Lief either via a subscription of $50 or a one time purchase of $299. 

This device is one of the best ways to both measure and action-ably improve HRV. Many find that after a few days using the device, they can detect when their HRV is dropping without it. This is a good tool to have for the general improvement of your nervous system function. 


Using HRV

The thing that makes HRV such a powerful marker is that it directly reflects the health of your nervous system. HRV is, in essence, a measurement of your resilience. Improving your HRV means improving your ability to adapt to change and stress, whereas declining HRV is an indication that you are burning out.

This section is about how to use HRV measurements from a device like those listed earlier, as well as how to improve your HRV scores over time. 

Develop Your Baseline

Like we mentioned in the last section, our goal is to discover our own baseline HRV and then use it to figure out our level of recovery. 

HRV fluctuates throughout the day, so the best way to begin developing a baseline is to measure your HRV at the same time every day. 

In my opinion, the best time to do this is in the morning immediately upon waking. This lets you get a measurement during a very consistent piece of your day when you are unlikely to be facing unexpected stressors. 

Devices like WHOOP and Oura can be particularly useful in that you are likely to end up wearing them consistently. This can provide data about your HRV trends for multiple parts of the day. 

However, I still recommend having a dedicated and specific time to do a reading first thing in the morning. I use the Polar H7 and the app Naturebeat for 5 to 20 minutes upon waking.

How long does it take to develop a baseline? I’ve heard recommendations as short as one week and as long as two months. The longer, the better, so I personally think you should get in a habit of consistent readings for at least a month before making assumptions about your baseline. 

With that said, you can begin to take action as early as day one. You don’t necessarily need to know your personal “normal” in order to adopt tactics for improving your HRV. 

The big reason we develop a baseline is so that we know when we are not normal. We need to know what a “drop” in HRV looks like so we can understand what it means. Start measuring your HRV daily for a month but use the data immediately. 

Using HRV To Detect Overtraining

Exercise is one of many things that can improve your HRV over time. However, exercise may lower your HRV in the short term. For example, if you do a workout and your baseline HRV is 70, you may see an HRV of 60 the next day. 

This doesn’t mean exercise is bad, it just means you are recovering from your workout. Over time, your HRV should return to 70 and then improve.

What you need to watch out for is an HRV score that is steadily declining. If you are working out regularly, you don’t need to take an off day every time your HRV is below baseline; If your HRV is declining for more than a couple days, it may be time to slow down. 

If, for example, I do a hard workout and my HRV drops 10 points for a day, I may still do a hard workout the next day. However, when my HRV drops even lower, then I’ll take a break or do lighter training til’ it recovers. 

You can feel things out, but if you HRV is declining in the long run, you are overburdening your nervous system. 

Many people have found that using HRV in this way allows them to not-only avoid overtraining, but to also avoid injury. I have found that since I began training based on my HRV scores, I rarely get sick or injured following training. 

Furthermore, when I do get injured, it almost always happens when I train during an HRV slump. 

HRV and Booze, Food, and Drugs

Another way you can use HRV is to test the effect of chemical intakes like food, supplements, booze, and drugs. Now, to be clear, I’m not suggesting you avoid taking prescription medication because it’s lowering your HRV scores, but it’s something you can be aware of. 

Booze and certain drugs or medications are known to lower HRV, but one of the more powerful ways you can use HRV is to measure things like supplements and food. 

It’s a little rudimentary, but tracking your HRV as you try a new diet can show you whether it is helping you or hurting you. Big plummets in HRV following a meal may indicate a food allergy or sensitivity, and a steady decline over the course of a few days may mean this new diet isn’t the best for you. 

In essence, you can use HRV to look at how additions to your life, be they food, new routines, etc. affect your nervous system. You can really get quite creative. Take it with a grain of salt, but I’ve even used HRV to test which room of the house I get the best sleep in. Lower scores might mean poorer airflow, mold, too many electronics, or just bad Feng Shui. 

Are you starting to see the value of this measurement? HRV is a constant assessment of your resilience. It tells you how balanced your nervous system is and whether you are improving, or declining, as you go about your life. 


Improving HRV

Many things improve HRV, but I want to discuss a select few that are known to be significantly effective. The 3 main things I focus on for improving HRV are exercise and movement, cold therapy, and meditation. 

Mindset & Self-Image

Before we talk about the actions you can take, I want to address mindset. Those who perceive themselves as stressed out display lower HRV scores, regardless of their athletic level. 

This is super important for all of us to remember: How you see yourself is more important much of the time than what you do. Anyone who has read material like mind-to-matter, psycho-cybernetics, or how to change your brain is already well familiar with this, but for everyone else, your mind-state is highly influential on your biology. 

So first and foremost, seeing yourself as a resilient and healthy person may be the most important thing for actually becoming that way. 

Exercise & Movement

It is well established that HRV is improved in athletic populations. In terms of kinds of exercise, high-intensity exercise such as CrossFit or powerlifting lowers HRV the most immediately following exercise, but yields improvement one the recovery period of one or two days has passed. Like other changes from high-intensity exercise, the long-term HRV improvements from this type of training may be better than other forms of exercise, if you don’t overtrain. 

I believe using high-intensity training is best paired with HRV measurement using a device so you can track overtraining. These kinds of workouts by-far yield the most benefits for our health, but they also offer the greatest risk of overtraining. In a world where many people train in this manner 5 times a week, tracking your HRV to prevent overtraining should be on the mind of every Crossfitter. 

Though high-intensity workouts seem to offer the best improvements for HRV if you don’t overtrain, aerobic capacity is more correlated with high HRV. I think this is because many people who do high-intensity training rather than aerobic training, end up overtraining. However, aerobic training like running or cardio does offer unique benefits for the heart that are not offered by other training types. 

Don’t get me wrong, you can still overtrain with cardio, but I often wonder if the fitness industry pendulum has swung too far into high-intensity training and away from aerobic training. 

I don’t think we need much, but personally I feel the best when doing 1 or 2 high-intensity workouts a week, and doing 2 to 3 low-intensity aerobic workouts such as running or light skill practice (handstand practice, etc.)

Basically, I train aerobically more often then I train anaerobically or at high intensity. The caveat is that I train light. I don’t train like a distance runner or a marathoner, and my aerobic work is rarely “hard.” 

Foam Rolling & Mobility

So in the long run, exercise improves HRV as long as you don’t overtrain. As far as improving your HRV scores right here and now, mobility work (especially foam rolling) is the tool of choice. 

What is the point of these activities? Nothing is proven, but I believe that activities that improve HRV in the short run can improve HRV in the long run. Furthermore, these activities are useful for improving things like sleep or focus. Anytime you need to lower your fight-or-flight and increase your rest-or-digest, these activities are powerful. 

The rest of the techniques in this section are focused on improving HRV right away. 

The Ready State is a powerful tool here. Independent from the mobility benefits, foam rolling before bed is well known to improve sleep quality. This may be because, for most people, it improves HRV. One more reason to do 15 minutes of mobility work if you feel stressed. 

I always do 15 minutes of mobility in the morning and 10 minutes of foam rolling before bed. I also do spot-checks throughout the day. After every 30 to 45 minutes of writing work, I’ll mobilize for 2 to 5 minutes. The Ready State library is stock full of material for this purpose.

Cold Therapy

Cold therapy has become popular in recent years for lowering inflammation and improving recovery from injury. However, outside of extreme cold therapy programs like The Wim Hof Method, there isn’t much data supporting benefits. 

At least not officially. Anecdotally, thousands upon thousands of HRV readings show that cold showers massively improve HRV. 

I try to regularly use cold showers to improve vagal tone and HRV. Most people choose to do cold showers in the morning, but my favorite time is actually 2 hours before bed. 

By boosting my HRV before bed, I am able to massively increase sleep quality. I’m hardly alone in this observation. WHOOP users, Oura wearers, and sleep trackers of all kinds have made the link between cold showers and improved sleep quality.

My only caveat is that these showers can be stimulating. I recommend taking them at least 2 hours before you actually plan on going to sleep, otherwise, the endorphin high from the shower can actually keep you awake. 

If you have a hard time taking straight cold showers, you can alternate between hot and cold. I’ve found this method to be far easier but just as effective. 

A basic hot-to-cold shower involves starting with hot water for 10 seconds and then switching to the coldest you can bear for 20 seconds. Repeat for 10 rounds and end on cold. 

You can change the intervals but always do the cold for twice as long as the hot.

Resonance Breathing & Meditation

Resonance breathing is a pattern of respiration that has been shown to tune HRV with the .1hz frequency. This frequency is part of the low-frequency band and represents the optimal autonomic nervous system balance. 

Institutes like Heartmath have found that we all have a specific breathing cadence that results in this resonance. These institutes are focused on training people to breathe in this way in order to lower stress and improve their HRV. 

To do resonance breathing and learn your personal rate, you’ll need a training device like the Emwave, inner balance, or the lief therapeutics device mentioned earlier. 

The best-case scenario is to use the Emwave or inner balance to practice resonance breathing for 5 to 20 minutes every day or to wear and use the lief system for a day or two. 

Over time with these systems, you can learn to recognize how it “feels” to be in resonance, and you won’t need them in order to breathe into this state. 

Since not everyone cares to drop $120 for this process, I can also recommend simple meditation. 

Having a mindfulness practice is free and highly beneficial. New to meditation? Not to worry. My favorite type of meditation is little more than closing my eyes and breathing. 

Every morning, I’ll “box-breath” for 5 to 20 minutes with my eyes closed. To perform box breathing, simply begin a 4 part breathing pattern of inhaling for 4 seconds, holding your breath for 4 seconds, exhaling for 4 seconds, and leaving your lungs empty for 4 seconds. 

See? 4 parts, like the 4 sides of a box. You can choose a different cadence based on your comfort and ability. I personally box-breathe with a cadence of 5 seconds for each part. This way I can also track how long I have been practicing. 

15 cycles of 5 by 5 box breathing is 5 minutes, 30 in 10 minutes, 45 is 15, and 60 is 20. You can also just set a timer, but I find that counting my cycles adds to the meditation experience. 

If you have a resonance training device, I definitely recommend using it daily. You really can’t beat a system that guides you to the optimal breathing pattern. However, I find that box breathing offers other benefits from the meditation experience. Even when I am regularly training in resonance breathing with a device, I still do a 5-minute box-breathing session sometime during the day. 

Diet & Other Factors

There are as many diets as the day is long, and what you eat affects your HRV. Heck, pretty much everything in your life can affect your HRV. Remember, this is a measure of your nervous system health. 

Optimal human nutrition is a topic for debate, but we should all strive to eat a whole-foods diet and eliminate ultra-processed foods. Whether carnivore or vegan, paleo or Wahls protocol, removing junk food is the first step to eating a better diet. 

So if you haven’t already, remove the soda, kick the Doritos, and return to foods you could butcher or garden. If it doesn’t grow in the earth or walk upon it, you probably shouldn’t eat it. 


Conclusion

Great freaking job you guys! You just survived one of the most technical guides to HRV I’ve ever seen. By the way, sorry about that, but I’m glad you stuck with it. 

I could have written a guide that just said “HRV = Nervous System. Track it and optimize your recovery.” But these articles have become a dime a dozen here on the internet, and they leave many readers with unanswered questions. 

By going a little deeper, we can understand what HRV actually is, how it’s measured, and how we can use these measurements to improve our own lives. Sure, most of the time it’s as simple as knowing your baseline and then working to improve it, but without knowing where these numbers come from, we miss out on the power to improve with efficiency and accuracy.

So, to re-cap, HRV is a measurement of the variance between your heartbeats over a period of time. This measurement may be the most useful marker you can track, as it reflects the resilience of your autonomic nervous system which governs your ability to face and handle stress. 

As you can imagine, HRV scores reflect many health markers, and improved scores are correlated with resilient mood, better heart health, lower risk of early death, and improved recovery from exercise and adaptability to stress. 

Good HRV devices use time-domain measurements such as SDNN or RMSSD, or frequency band measurements. Understanding these measurements can give us unique insight we would otherwise not understand. For example, good low-frequency measurements mean good autonomic nervous system function and we can use breathing to increase these values. We also know that SDNN measurements really aren’t useful unless you are measuring with an ECG device for 24 hours.

With this information, we can make an informed decision in picking a device to measure our HRV.

At a minimum, we need something that can measure our RMSSD HRV for 20 minutes every morning upon waking. We can use this consistent information to discover our baseline HRV, and then use this value to see if we are recovering well, or burning ourselves out. 

Good lifestyle choices such as exercise and a whole foods diet will affect our HRV in the long run, but our emotional state may matter more. Seeing ourselves as stressed and unhealthy can undermine athleticism, so first we need to learn to see ourselves as healthy and relaxed. Beyond that, we can definitely take action to quickly improve our HRV. 

Cold therapy, mobility work, and meditation all directly improve HRV scores. Using these methods before bed can give you a one-two punch of improving your HRV and boosting your sleep quality, which also improves HRV. 

If you can afford it, one of the most powerful ways to train your HRV is a resonance training device. The Heartmath Institute has several such gadgets, and the Lief Therapeutics wearable is phenomenal for this as well. 

And there we have it! HRV is a big topic, and there is so much more to it than this article, but now you have a foundation of understanding. I know it got pretty technical, but with this information, you can confidently navigate gadgets and techniques for improvement without confusion. 

Thank you so much for reading, and I hope this helps you continue improving your Ready State!