Treatment option: Heart Rate Variability (HRV) for dysautonomia and exercise intolerance

Using HRV to help restore autonomic nervous system balance

When brain injury creates dysautonomia

One of the hallmarks of post-concussion recovery is an elevated sympathetic nervous system—an overactive “fight or flight” response—complete with heightened levels of vigilance and stress hormones. It’s as if a car alarm is going off in your head almost 24/7, an alarm that may be silent to others, but is easily measured via biofeedback.

Needless to say, matters only get worse with the inevitable arrival of a new stressor—a sudden loud noise, being startled, an emotional argument, a confrontation, a loud environment, etc. This is due in part to a complicating factor: a diminished ability to suppress or filter incoming sensory information, which may have been caused by downstream damage to the thalamus.  

The intractable imbalance of the autonomic nervous system is known as dysautonomia. It makes sense that the autonomic nervous system would be disregulated—since the brain is the centerpiece of the nervous system, an injury to the brain is an injury to the nervous system.

Since the symptoms of dysautonomia include dizziness and brain fog, two of the more common symptoms of post-concussion syndrome, you can imagine how difficult it will be to resolve those symptoms if it’s unclear whether they’re being caused by the injury to the brain or by the dysautonomia.

If one of your challenges is engaging in exercise without triggering your symptoms, dysautonomia is likely at play. The autonomic system regulates one’s heart rate in response to exertion.

Restoring autonomic balance

One of the keys to your recovery is learning how to bring your autonomic nervous system back into balance, and that typically means activating the parasympathetic nervous system, sometimes knows as “rest and digest.”

There are two approaches to doing this, one is top-down (brain to body) and the other is bottom-up (body to brain). In either case, the vagus nerve is involved. This long nerve pathway is a two-way neurological street, and around 2/3 of the traffic (information, neurological signaling) runs from the body to the brain. So “using the body to control the brain” makes sense in this context.

One of the behavior tools that can help ease dysautonomia and steadily restore greater autonomic nervous system balance is called Heart Rate Variability or HRV. Let’s dive into that.

What is Heart Rate Variability?

Heart rate variability or HRV is simply the variation in the time interval (often milliseconds) between one heartbeat and the next. In other words, it’s a measurement of the inconsistencies in the precise timing of those beats. These small variations can occur in response to all kinds of things, including rapid changes in body position, exertion—and the state of one’s nervous system.

Heart rate is controlled by the autonomic nervous system. So your HRV can be thought of as a kind of dashboard gauge showing the relative balance between the parasympathetic and sympathetic systems—the overall tonic of your autonomic nervous system.

When your HRV is high, that’s a biomarker for things like good emotional regulation, good decision-making, high attentional capacity, and other positive states (as well as long term health outcomes).

Low HRV reflects the opposite. It reflects increased fight or flight activity. This is great news—it means that by increasing your HRV, you can decrease fight or flight activation.

How to do HRV training

HRV training is essentially breathing exercise + biofeedback. It can include athletic training (many athletes use it to improve performance).

Since HRV training involves real-time measurements of millisecond intervals between heartbeats, it requires some technology to perform and track those measurements. These technologies are now fairly inexpensive and readily available (I’m guessing they will one day be available in something like an Apple Watch or other discrete wearable).

I personally use an app on my phone called Elite HRV in tandem with a device called the CorSense, which is made by the same company. The app can also be used with hands-free devices from Polar so you can monitor HRV while exercising.

The Elite HRV app allows you to take a baseline reading every morning. The reading shows where you fall on a spectrum between too much sympathetic and too much parasympathetic activation. If you’re in the sweet spot in the middle, you get a high rating and a green light to proceed with training etc.

It should come as no surprise that HRV training is often used by athletes and people who are keen to boost their physical and cognitive performance. After an intense bout of strength or endurance training, an athlete can check HRV and decide whether to continue with training or shift into recovery.

The app includes these breathing exercises:

  • Deep Calm

  • Ease Anxiety

  • Relieve Stress (box breathing)

  • Balance

  • Awaken

  • Focus

As you can see, these exercises exist on a spectrum of nervous system activation and you can use them to increase calm as well as alertness.

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Resonance breathing

Everyone has an ideal resonance breathing rate—a rhythm of inhalation and exhalation that balances one’s nervous system. The average is about 5.5 seconds in and 5.5 out.

Your HRV training will involve some level of experimentation to determine what your own resonance breathing rate is, which you can then use to balance your autonomic nervous system. While you could intuit this, HRV training makes it easily quantifiable.

The first time I did resonance breathing, I felt some tingling in my limbs and near the base of my head. After 20 minutes of resonance breathing, I felt calm yet alert.

Incidentally, one of the tests for dysautonomia involves hyperventilation, which makes perfect sense.

Integrating HRV into rehabilitative exercise

Multimodal concussion recovery clinics sometimes use HRV biofeedback to help their patients before and after they perform rehabilitative exercises. This approach helps provide an on- and off-ramp of up-regulation and down-regulation. It may help prevent the dreaded overstimulation that can prevent you from continuing with rehab.

This means you can use HRV for the same purpose. Within the Elite HRV app are preset breathing exercises called Workout Priming and Post Workout Recovery.

HRV training’s attentional benefits

We’ve already established that brain fog is a symptom of both TBI and dysautonomia.

Below is a small collection of quotes from Wikipedia that should inspire you to take up the practice of HRV for its cognitive and attention-boosting benefits:

  • A systematic review of HRV and cognitive function suggested that resting HRV can predict individual differences in attentional performance.

  • Decision-making skills are found to be indexed by HRV in several studies.

  • Decision making is negatively affected by lower HRV and positively affected by higher levels of HRV. Most importantly, resting-state HRV was found to be a significant predictor of cognitive functions such as decision making.

  • A group of researchers found that groups with high anxiety and low HRV have poor attention.

Can other things help ease dysautonomia?

Apart from HRV, there are other breathing exercises that can help regulate the autonomic nervous system, including certain breathing techniques used in meditation and the Wim Hof Method (which combines breathing exercises with cold exposure). Re-establishing your circadian rhythm is also an essential piece of the puzzle.

When the imbalance has us shifted into perpetual fight or flight, anything that helps promote a rest and digest response is going to add another tool to your recovery toolset. HRV training is one of those tools.

Wrapping up

It’s common for a concussion or TBI to lead to some level of dysautonomia, over-active fight or flight, and under-active rest and digest. Since the symptoms of dysautonomia overlap with TBI and post-concussion syndrome, it can be hard to resolve TBI symptoms without addressing dysautonomia.

Establishing balance between the two halves of the autonomic nervous system can be done via a top-down (brain to body) approach or a bottom-up (body to brain) approach. A tool that falls under the latter category is HRV training, which is used by athletes and others who want to optimize their health and performance.

Since heart rate is controlled by your autonomic nervous system, HRV helps you gauge the state of that system. Unlike some other biomarkers of health, HRV is relatively easy to influence and improve, but it does involve the use of devices that can track HRV in real-time.

As you become more adept with HRV training, you can integrate this tool into your rehab routine, for example, by doing HRV breathing exercises before and/or after therapies that might trigger your symptoms.


Brainwave is an informational resource for people whose symptoms haven’t resolved after a concussion or mTBI. I endeavor to present this information in a clear and concise way, spelling out what’s backed by science and what remains unknown. Nothing here is meant as a substitute for professional medical advice, diagnosis, or treatment. I am not a physician or a healthcare practitioner of any kind; I’ve simply had a lot of sports-related concussions and had to learn this stuff the hard way. If you found this information helpful or know someone who might benefit from it, please share and subscribe to Brainwave.