What is heart rate variability? Group of orange stethoscopes on a pink background
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If you own a smartwatch or have been with people who own smartwatches, you may have come across a metric called HRV, or heart rate variability. On the internet and social media, it looks like HRV is a health condition that many people start or like to self-monitor. Vivian Mo, Dr. Whoop, Fitbit, and other smart health and fitness trackers). “When I typed in ‘heart rate variability’ into Google, a definition came out of it, and right after the definition was just all devices that measure HRV,” she adds.
Americans these days are also more proactive about their own health, tracking their health data themselves. Interest in HRV could also be related to the growing focus on wellness and lifestyle medicine, as HRV can be a good metric for improving stress regulation and measure healthy lifestyles, says Tamara Horwich, MD, associate clinical professor of medicine and cardiology at UCLA’s David Geffen School of Medicine.
Perhaps you are one of the many people who monitor their HRV. Or maybe you’re one of the many other people who notice the HRV on their device or app but aren’t sure what to think of it. That’s why we asked the experts to explain – and here’s what you need to know about it.
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What is heart rate variability?
Heart rate variability is the variance in timing between each heartbeat, says Dr. Mo. She explains it this way: When you are at rest, your heart rate is around 60 beats per minute. But if you looked very closely at the timing between each beat, you would find that it doesn’t always beat every second. Sometimes your heart beats every second and sometimes it beats after 1.1 seconds or 0.9 seconds. There is a difference or variance in timing between each beat. This is your heart rate variability.
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A normal HRV for people in their teens and twenties averages between 55 and 105 milliseconds, but most people aged 60 and over have lower heart rate variability averaging between 25 and 45 milliseconds.
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What does heart rate variability tell you?
HRV is a way of measuring what is happening to your autonomic nervous system, which is the part of the nervous system that regulates functions like blood pressure and breathing. The autonomic nervous system has two sides, explains Dr. Horwich, the sympathetic nervous system (SNS), which is involved in the “fight or flight” response that increases your heart rate, and the parasympathetic nervous system (PNS), which helps you “rest and digest” and lower your heart rate.
These two sides always face each other to create some kind of balance in your body. HRV is a reflection of what is going on in the sympathetic versus parasympathetic “struggle”. If you track your HRV for over 24 hours and find that it’s lower than usual, it could mean the sympathetic nervous system is dominating and being activated for longer than necessary, while a higher HRV is a sign of more parasympathetic inputs into the heart, explains Dr. Horwich.
Is there a “better” or “healthier” HRV?
Dr. Horwich explains that it is healthy to have more parasympathetic inputs into the heart. So if you have been measuring your HRV over a long period of time, say 24 hours, and it is higher than your usual HRV, it could be considered better for your health. On the other hand, if you’ve done the same monitoring over 24 hours and your HRV is lower than usual, “generally it is a sign that something is wrong with that person’s lifestyle or their heart health,” says Dr. Horwich.
While this seems simple enough, she adds that it may not always be because the HRV is also a reflection of many other things that are going on in the body. “There are complex mechanisms, various feedback loops, and other things that go into heart rate variability,” she explains. This is one reason why doctors don’t routinely use HRV as a measure of their patients’ health, as there are more objective and definitive metrics that they can use.
What lifestyle factors affect HRV – good and bad?
You now know that your HRV naturally decreases or “worsens” as you age. Aside from just getting older, you may also notice lower HRV if you are under a lot of stress, dehydrated, drink a lot of alcohol, eat unhealthily, do less physical activity, and sleep poorly, says Dr. Mon
The opposite can also happen: your HRV can rise as you begin to manage stress and improve your food choices, exercise regularly, stay hydrated, drink less alcohol, and sleep seven to nine hours each night. Like Dr. Mo points out, it is possible that a 65 year old who is physically fit and active could have a higher HRV.
“You saw that when people get involved [healthy lifestyle behaviors], they tend to have better heart rate variability, “she says.” But they don’t really know the physiological basis for it right now. “
Dr. Mo says it may be related to the effect of these behaviors on the autonomic nervous system. Dr. Horwich agrees. “For example, if someone is not eating healthy, this is when your sympathetic nervous system can be activated, and if it is activated all the time, it is not healthy for your body,” says Dr. Horwich.
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How can you track your HRV?
According to Dr. Horwich, the most accurate way to track heart rate variability is to take a continuous electrocardiogram (EKG), which records the electrical signal from your heartbeat. In order to record the heart rhythm over a certain period of time, the cardiologist has the person wear a so-called Holter monitor or patch, which records an EKG while on the move.
What about smartwatches? Dr. Horwich says smartwatches’ HRV is based on the heartbeats it detects from your wrist pulse, so it may not be as accurate as the measurement you get from an EKG that reads the heartbeats from your chest.
However, it doesn’t mean you need to discredit this number because your smart tracker’s HRV can still be something to talk to your doctor about if you’ve noticed a sharp change over time. But most importantly, if you’re tracking it on your device, don’t get upset about it as it may not be 100 percent accurate (or tell you the full story). So you can take note of it, acknowledge it, tell your doctor – but don’t panic about it.
How much attention should you pay to keeping HRV high?
While you are encouraged to pursue the healthy lifestyle behaviors mentioned above, using the HRV as your end goal (to see it go up or down) may not be very helpful or motivating. In most cases, that adds so much to an individual’s heart rate variability, and “it’s hard to control so many variables in your life just to improve your heart rate variability,” says Dr. Mon
It can be more worthwhile to track these healthy behaviors and measure their effects using other metrics – like how far you can run without catching your breath, or how high your anxiety or stress levels are.
As cardiologists, Dr. Mo and Dr. Horwich both that they don’t use HRV very often to determine what treatment a patient needs because it’s not currently recommended for clinical practice in cardiology.
“In my practice, I know that improving a patient’s diabetes, cholesterol levels, or blood pressure means that their overall health is improving. Therefore, there is no need to work towards improving HRV in addition to all of these measures,” says Dr . Mon
If you already own a smartwatch that tracks HRV and you notice that it is rising or falling over a long period of time, don’t hesitate to let your doctor know. If anything, discussing it with them gives you some peace of mind.
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