Can HRV Really Predict Illness?
What would you do if you knew a virus was about to take you down.
Back in 2004, I was rolling over every morning and pressing my thumb into the indent of a small, square turquoise device. I watched as the light turned my thumb a pulsating red. I was measuring my heart rate variability, or HRV. I had recently returned from Ben Greenfield’s Super Human conference, where he said that if you’re going to measure anything, track your HRV because it’s the single best predictor of illness.
Predicting illness? A crystal ball into my health? Sign. Me. Up. These were the early days of biohacking, and I was here for it.
Think about it. What could you do if you knew that you were about to be sidelined by a bug? You could pull out the juicer, gargle with salt water, load up on zinc and elderberry, schedule naps, prep the mustard plaster, do extra breath work and get through it fast.
As excited as I was, my compliance with the turquoise thing-a-ma-jig was low, and eventually, it was lost. But ever since, I’ve been fascinated with HRV and what it can tell me about my health.
Twenty years later, HRV is still a popular topic, but thankfully, it’s much easier to measure. If you want to measure HRV (or heart rate, body temperature, or VO2 max….), you can get it instantly from any wearable tech on the market.
My wearable tech of choice is Garmin. I recently purchased a Garmin watch to help me train for a cycling trip to Italy (you can read about my love-hate relationship with this watch here.) I am still curious about how HRV is measured and how it knows I’m about to head to bed with a box of Kleenex.
Let’s dive in.
What Exactly is HRV?
You may think your heart rate is steady and beats at the same rhythm, but there are time fluctuations between heartbeats. These fluctuations are only milliseconds and are undetectable to us.
Therefore, HRV is about the irregularity between heartbeats. And this irregularity is very desirable. Normal HRV can range from 20-200 milliseconds depending on age, sex, fitness level, stress and genetics.
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When you first start using wearable tech, it won’t immediately reveal your HRV. It will take a few weeks to measure and create your baseline. HRV is highly individual, so once your baseline is established, it’s only helpful to compare your measurements against your baseline and not anyone else’s.
Typically, for any numbers related to our health, we aim to get lower - low resting heart rate, low blood pressure, low cholesterol - but HRV is the oddball where we want higher numbers.
A higher HRV is an indication of how adaptable you are and how you can quickly react to changing circumstances. A high HRV is linked with overall “good” health, while a low HRV is linked with overall “poor” health.
The magic of HRV is that it’s a peek into your autonomic nervous system (ANS). Your ANS helps you respond to daily stress and regulates some important systems, such as heart rate, respiration and digestion. ANS controls all the keep-you-alive functions without any conscious thought.
Specifically, HRV indicates the balance between your parasympathetic nervous system (rest and digest) and the sympathetic nervous system (fight or flight).
When your HRV is high, you’re closer to the chilled-out, rest and digest state. It indicates good fitness and the ability to recover from stress well. This is good news for your heart and emotional health.
When your HRV is low, you’re closer to the fight or flight state and in a state of stress, illness or overtraining. This is not so good news for your heart and emotional health.
What Does a Drop in HRV Mean?
A drop in HRV indicates an imbalance in your autonomic nervous system. If your HRV goes low for a few days, it usually isn’t much to worry about as long as it recovers within your baseline.
But if it stays low, it indicates that your fight or flight (sympathetic nervous system) has been activated due to mental or physical stress. Mental stress can come from relationships, work, kids, or simply the news(!). Physical stress can come from over-training without giving your body adequate recovery time.
But other factors can also drop your HRV such as a late meal, a late workout or alcohol.
How Can I Improve My HRV?
While there are influences on our HRV that we can’t change, like age and gender, there are several things we can control that can improve our HRV.
Train Appropriately. Too much or too little exercise can lower your HRV. Watching your HRV respond to your training schedule gives you insight into how much recovery you require.
Manage Your Stress. Observing your HRV can show how stress in your everyday life affects your nervous system. Find ways to manage your stress with breath work, gentle movement practices such as yoga.
Drink Water Not Alcohol. Stay hydrated and limit your alcohol consumption. Even a few drinks at night can affect your sleep quality and lower your HRV.
Get Lots of Sleep. Low quality sleep and sleep deprivation is guaranteed to tank your HRV. Find a sleep routine to properly recover from the stresses of the day.
Eat Well. Eat your veggies! A study published in the American Journal of Clinical Nutrition showed that eating fruit, veggies and fish can lower your HRV.
So… Can HRV Really Predict Illness?
Because HRV is an extremely sensitive marker to your body’s stress, it is helpful to indicate a looming illness. Once you have an established baseline, and notice a sudden drop, it does indicate that the immune system is stressed. But what exactly is stressing the immune system is what you need to determine. If you can rule out poor sleep, alcohol consumption or excessive stress, then yes, it may indicate that your immune system is fighting a bug.