I'm on a quest for one biometric to rule them all. Wanted: One objective measure to summarize overall state of health. Must be easy to take, affordable, accurate, consistent, comprehensive, and most importantly, actionable.
Modern science has crowned heart rate variability (HRV) the unequivocal winner.HRV quantifies the impact of everyday lifestyle choices on your physical, mental, and emotional health. Click To Tweet
Use HRV to become a more resilient human, capable of handling greater stress, and making better choices. Before we get into the nuts and bolts of tracking and improving your own HRV… let's start with the basics.
What is HRV & Why Track It?
Your heart doesn't actually beat at an exact rhythm. A healthy heart varies its paces from one heart beat to the next. Heart rate variability is the biometric that captures that slight variation between beats. Think of it like morse code. And different messages correspond to different intervals between beats.
What kinds of messages?
Your brain and nervous system constantly communicate. Transmitting information about: hormones, exercise, stress, nutrition, recovery, environment, breathing patterns, light exposure, and even relationships. Tracking heart rate variability helps you correlate decisions with their brain & body impact (positive and negative). Long before they're detectable other ways.HRV demonstrates the intricate link between psychological and physiological processes. Click To Tweet
More precisely, it measures the balance between the sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) branches of your nervous system.
In other words, HRV measures stress. Stress that you may not be aware of. But it's far more useful than that:
HRV demonstrates how the psychological processes of the brain, heart, and emotions influence each other and the rest of your physiology.
Researchers can predict the way you feel with 75 percent accuracy using nothing but HRV data.
Scientists and biohackers use HRV in cool ways:
- Building resiliency to control the fear response
- Reducing stress and anxiety
- Improving attention
- Predicting how well anti-depressants will work
- Estimating user traits
What kind of traits?
HRV can accurately predict age within two years.
Science of Heart Rate Variability
Now you have the “what” of HRV. In order to take advantage of this technology, you should know what to look for and how to interpret scores.
How HRV Works
Several algorithms count and interpret the time between each beat. The algorithms get confusing. Each interprets data in different ways.
Some are better than others. In case you're interested in further research, at the time of this writing the common algorithms include:
The two bolded algorithms are most accurate. Any respectable HRV wearable will use one (or both) in their product.
Optimal HRV Scores
First, heart rate variability varies massively from person to person. It's sensitive to intricacies of your unique biology. Comparing your scores to your friends is meaningless.
But what do the numbers mean?
Think of HRV as a gauge. On one side you're highly stressed (low score). On the other, totally chill (high score).
A highly-relaxed score of 85 may seem better than 80.
But maybe not.
- Higher scores aren't always better.
- Lower scores aren't always worse.
You're normally somewhere in the middle of the window. Middle scores signify a healthy balance between sympathetic and parasympathetic.
Why is a higher HRV sometimes suboptimal?
Extraordinary scores can indicate your parasympathetic branch doing everything it can to recover and bring you back into balance. You've overtaxed yourself.
Your optimal score depends on your lifestyle, schedule, physical and mental workload, routines, and other forms of stress.
How to Measure HRV
There are three main types of HRV devices:
- Apps: provides other ways of using HRV data. Some don't need a wearable.
- HRV monitors: passively identify changes in HRV, requiring the wearer to test different lifestyle changes.
- HRV trainers: actively teaches the wearer effective ways to increase HRV.
Certain apps can unlock your wearable's data and centralize the information into one place.
Especially for those with multiple devices, third-party apps provide more functionality and greater access to your data.
Two apps dominate third-party HRV measurement:
Elite HRV describes their app as: “The free Heart Rate Variability app that emphasizes professional quality and accuracy.”
Indeed, I liked their easy-to-understand daily scoring. A number between one and ten describes your readiness. It's also compatible with 11+ wearables as of now. The app even shows your realtime HRV.
HRV4Training is the best overall app for both professional athletes and teams. It's scientifically validated, feature-packed, and even works with the Oura & Apple Watch. The drawback is the $9.99 sticker price.
Best of all, HRV4Training works without a wearable, using nothing but the iPhone camera.
HRV Monitoring Devices
These days every advanced wearable measures HRV.
Popular, cutting-edge devices all use the ideal algorithms. Although the Apple Watch uses the flawed SDNN algorithm, data collected via the “Breathe” app is still semi-accurate. It just won't show the same level of granularity.
I wrote an entire post dedicated to uncovering the top 10 advanced biofeedback HRV monitors. A few of which include:
Just as important as the algorithm, when you take HRV measurements matters.
For meaningful data, you must hold lifestyle variables constant. One easy way is to compare HRV every day just after waking. Before any urgent emails, texts, or emotional events can add stress.
Especially if using the Apple Watch (and check out this useful article).
HRV Biofeedback Training Devices
HRV training devices coach you to better tolerate stressful situations.
They're a level above passive HRV monitors.
I use an app on my Garmin smartwatch.
The good devices teach you how to overcome stress by balancing emotions and going into a state of coherence.HRV trainers provide real-time coaching to improve your heart rate variability. Click To Tweet
That same list as above also includes the best HRV biofeedback devices. They tend to be slightly more expensive but leaps and bounds ahead of passive monitors. Other popular HRV trainers include:
Causes of Low HRV
Humans today could use an HRV boost.
Chronically low HRV is highly correlated with greater risk of death from all causes.
What does a low HRV measurement mean?
Low HRV signifies greater activation of the stress response (sympathetic nervous system). This is the process responsible for releasing massive amounts of energy, but bursts of energy come at a cost. You cannot digest, relax, and repair in the sympathetic-dominant state.
Even positive forms of “eustress” like exercise and fasting hurt HRV scores temporarily. Only with adequate recovery do they elevate your baseline.
Seemingly anything that affects your biology can impact HRV. Common causes of low HRV include:
- Overtraining or pushing yourself hard without adequate recovery eventually breaks down the body and causes serious symptoms.
- Poor diet. Macronutrients aside, processed foods can interfere with recovery and repair.
- Improper breathing is one of the fastest ways to alter HRV (more on this later). Do it wrong all day, and your score will suffer.
- Electrosmog pollution. Electrosmog blocks the calcium channel “doors” of cells open. Too much calcium rushes in, overstimulates the cell, and activates the stress response.
- Not enough clean water. You need plenty of good, structured, natural water to hydrate. See my article on deep hydration to understand how the best water comes from your food and lifestyle.
- Alcohol ruins your sleep quality (as I discovered through my Oura ring). Poor quality sleep leads to low HRV.
- Sleep deprivation annihilates HRV, a pattern I observe from hundreds of nights of Oura sleep data.
- Stress from negative thoughts & emotions. Work, toxic relationships, and bad environments directly lower HRV score.
In summary: stress drops HRV. Resilience building activities increase HRV.
Plenty of things boost HRV.
Hacks to Increase HRV
“This is because it is not how high HRV is that is important, it is how well you can modulate HRV that demonstrates having control of your nervous system.”Unknown
Recall from earlier that HRV quantification measures the balance of stress and relaxation. The control switch is called the vagus nerve.
Anything that tones or strengthens our vagus nerve should increase heart rate variability.
Self-hacked wrote an article featuring an astounding 32 different ways to stimulate your vagus nerve and increase HRV:
I'm a big fan of the following:
- Breathwork practice: consciously controlling your breathing pattern through the Wim Hof Method, box breathing, or Patrick McKeown's The Oxygen Advantage book exercises are among the most powerful methods of increasing HRV in real-time.
- Exercise: intense high-intensity interval training (HIIT) exercise like slow strength training effectively improve HRV.
- Clean diet: removing inflammatory foods reduces sympathetic stress.
- Infrared sauna: multiple studies found that sauna use increases HRV. Check out my article on building your own near-infrared sauna for about $150.
- Sunlight exposure: normalizes energy levels and circadian rhythm. Believed to increase HRV. Try sun gazing for additional benefits.
- Grounding: walking on bare earth rebalances the autonomic nervous system.
- Cold exposure: cold water deactivates fight-or-flight. Learn how to painlessly start taking cold showers here.
- Singing: another free practice that activates the vagus nerve.
- Meditation: multiple types of meditation increase HRV.
- Supplements: stress reduces HRV, and certain supplements blunt stress. Top choices include Ashwagandha, L-Theanine, adaptogenic mushrooms, and Phosphatidylserine. Make sure to buy from high-quality supplement brands.
Heart Rate Variability: Measure, Track, Improve
Full-body insight in one metric?
Look no further than HRV. This snapshot of the nervous system is a great proxy of overall health. Not just physical health, but mental, and emotional too.HRV correlates the external world with internal biological changes. Click To Tweet
Using nothing but HRV, researchers can accurately predict your age and the way you feel. Learn to control it, and your wellbeing increases.
Not interested in new tech? You can start simply, just by adding one HRV-boosting habit.
For quantitative folk, choose a HRV monitor from the list above. They gamify building new healthy habits. And once ready, upgrade to an advanced HRV biofeedback training device.
What's your favorite all-in-one biometric?