Monitoring Heartrate Variability to Help Manage Your Illness
What It Is
Heart rate variability (HRV) is a measure of the variation in time between consecutive heartbeats.
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HRV can be seen in the subtle heart rate fluctuations with respiration: when we breath in, our heart rate speeds up slightly; when we breathe out, it slows down slightly.
HRV reflects the balance between the sympathetic and parasympathetic branches of the autonomic nervous system, which regulates the body’s stress response.
Why It Matters
As an indirect look at how a person’s autonomic nervous system is functioning, HRV can reflect overall health.
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People with ME/CFS, Long COVID and other chronic illnesses often have lower heart rate variability, signaling that the body is under strain and not functioning optimally.
HRV values, which vary within the day, day-to-day and under different conditions, typically range from 20 to 200 milliseconds, with a higher HRV being a sign that a person’s autonomic nervous system is highly responsive (a good thing).
For people with ME/CFS and Long COVID, low HRV has been linked to poor sleep, cognitive issues and increased anxiety and pain.
How to Use It
For people with ME/CFS or Long COVID, HRV can be used to help with pacing and illness management in a few ways:
Average HRV Over Time
If your average HRV (taken at the same time, in the same position and under similar conditions) declines steadily over weeks or months, even by a small amount, it may be a sign you are overdoing it or that your condition is worsening.
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Your illness could get worse very gradually and you may not notice. Monitoring your HRV over time can alert you to be more cautious with your exertion, and may help avoid a crash.
HRV to Test What Works (and What Doesn’t)
Some people use their average daily HRV (along with regular symptom tracking) to test for triggers (things that make symptoms worse) and verify if a new medication, behaviour or treatment is helping.
For example, limit your stress, change your diet, try a new medication, or rest more often (without other major changes), and monitor your daily HRV to see if it goes up. Or use your daily HRV to help monitor if going back to part time work is being tolerated.
HRV in the Morning
For some, measuring HRV in the morning can be a hint as to general health and available energy for the day.
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For example, for one patient, lower morning HRV tends to correlate strongly with worse head, body, and joint pain for the day.
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HRV to Demonstrate Crashes “Objectively”
Some doctors may feel more confident to diagnose ME/CFS or Long-COVID if you can provide data showing a low HRV overall, or decreasing (worsening) HRV correlating to various actions or symptoms.
HRV can help in a similar way with family and friends.
One patient says:“the most surprising benefit I found from HRV tracking has been being able to objectively demonstrate ‘crashes’ to others.”
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How You Measure It
HRV measurement is much more sensitive to error than heart rate. You will need a very reliable device that can detect your heart beat, and software that can analyze the data and calculate your HRV (Apps usually give HRV on a 1-100 scale). HRV cannot be measured and calculated manually.
What to Think about for Devices and Apps
Some people report that wristbands like Fitbit or cameras on smartphones are not good enough and that only a chest strap (like Polar) will work properly.
You can also get a portable ECG for home if you want to (like AliveCor or QardioCore), but most people do not feel this is necessary.
Others say wrist, arm or finger devices such as Apple Watch, Garmin , and Whoop (or even the camera on their smartphone) work fine.
You can use an electrocardiogram (EKG) in a medical setting or have your doctor send you home (usually for a day or two) with a medical-quality monitor, if you want.
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