Healthy Outlook: What is heart rate variability (HRV), and what does it mean for your health?
photo by: Mackenzie Clark/Journal-World Photo Illustration; Shutterstock Images
Not too long ago, if you’d asked the average guy about wearable technology, he might have gestured to the Walkman clipped to his cargo pants, next to his beeper.
The phrase has taken on an entirely different meaning. Today’s wearable technology gives us access to a massive amount of our own medical data — whether we understand it or not.
One of those numerical treasure troves is heart rate variability, or HRV. It’s gotten a lot of attention in recent years in the world of athletics and fitness, as the technology to measure and track it has become more accessible for home use. In fact, a 2018 update to the Apple Watch added that stat to its capabilities.
But what is it, and why do people care?
Put most simply and generally, variability in our heart rate is something we want. It’s a good thing.
Dr. Andrew Sauer is a cardiologist and medical director of the University of Kansas Health System’s Center for Advanced Heart Failure & Heart Transplantation. He explained that the heart rate naturally oscillates — for example, it goes up when we exercise and when we experience stress or anxiety; it goes down when we recover and when we sleep.
“A sign of health is that the heart rate will respond to the normal interactions of the brain and the kidneys in a predictable way, and a sign of cardiovascular disease in general is when we start to lose those normal variations,” Sauer said.
photo by: University of Kansas Health System/Contributed Photo
Joseph Weir, chair of KU’s Department of Health, Sport and Exercise Sciences, holds a doctorate in exercise physiology. He said HRV is driven by the autonomic nervous system, or ANS — basically, the functions your body manages on its own, such as heart rate, blood pressure, temperature, blood flow distribution and so on.
He provided the explanation he gives to undergrads. He said the ANS comprises two branches: the sympathetic branch, which governs our “fight-or-flight” response, and the parasympathetic branch, nicknamed the “rest and digest” branch. He said — although this is a gross oversimplification — that in general, the more variability, the healthier your system and the more you’re tilted toward the parasympathetic side.
Tracking the number over long periods could help provide an indication of overall cardiovascular health.
photo by: University of Kansas/Contributed Photo
“What is pretty clear is that if you get more fit, heart rate variability improves,” Weir said.
HRV readings and athletic recovery
There has been research on HRV for decades now, but it has much more recently become something that people can monitor regularly on their own, using a smartphone app. But there are lots of apps out there that measure a lot of different numbers — some more intricate than others.
Weir noted that the specific numbers measured may differ by vendor, and he would suspect some of it is proprietary in terms of the data that apps collect and the readings they provide.
“Healthy systems have more variability, and all these different numbers that are out there are quantifying the amount of variability in different ways,” Weir said.
HRV tech proponents say that athletes and fitness enthusiasts can use the data to measure their body’s recovery and to watch for warning signs of overtraining. Weir said he’s still skeptical about how much HRV changes during periods of overtraining.
“I think it’s probably a little bit more popular than the data warrants right now,” he said. “I’m not saying it’s not useful; I’m just saying that there’s enough studies out there that kind of makes me a little bit skeptical about the overtraining stuff.”
Chris Dellasega, owner of Athletic Strength Institute at 720 E. Ninth St., No. 3, holds a master’s degree in exercise science and is a certified strength and conditioning specialist.
Dellasega also serves as a strength coach for the USA Cycling men’s track team, and he’s actually hoping to start using HRV data to help those endurance athletes who are hardwired to keep pushing themselves.
“Sometimes trying to get them to back off their training a bit can be a little bit tough,” he said. “But the cool thing about things like HRV is … it is a physiological value. It is something that you cannot cheat.”
Dellasega agreed, though, that HRV is “not the end-all be-all” measure of recovery; there are a lot of different ways to measure it, each with its own perks. He also cited grip strength, basic resting heart rate, and cortisol to testosterone ratios — but the latter involves blood testing, which is not feasible for most people on a day-to-day basis.
“I think that using multiple methods to assess someone’s recovery generally paints a better picture than just using one method,” he said.
Sauer said that in regard to this technology, one concern is about “almost excessive diagnostic monitoring,” which could lead to overtreating patients by giving them medicine or procedures they don’t need — plus the risks, side effects and complications that come with that.
“I think overall it’s good that patients are having more information in their hands, and generally it’s an empowering thing. And I’m supportive of it; I think most people are,” he said. “I think we just have to have patients understand that for specific questions about what their device is showing for them, those questions are best suited for a cardiologist or at least a very good primary care physician that they know and trust, that knows them.”
Another concern Sauer raised is that some people may start to obsess over this kind of data, therefore bringing more stress and anxiety upon themselves — perhaps even an anxiety disorder if they focus on it too much, he said.
Dellasega agrees, and he said the same theory applies to some people who are trying to lose weight and might weigh in every day or even twice a day. That, then, can lead to obsessive calorie-counting.
“It doesn’t make any difference what the goal is. The only way to obtain that goal is to consistently do what you need to do over time to get you there, and obsessing about those numbers is not the way to do it,” he said.
My HRV experience
I bought a heart rate-sensing chest strap and downloaded an app called Elite HRV back in May, and I’ve been monitoring my HRV fairly consistently since then (in hopes of one day penning this article).
Elite HRV connects to the chest strap to collect a two-minute “morning readiness” reading, and over time it determines your baseline. It breaks down the numbers from your reading and allows you to input your mood, how much sleep you’ve gotten, whether you exercised the day prior and various other factors, so that those are available alongside the HRV data.
This particular app uses several numbers to determine the morning readiness score, which is a scale of 1-10 intended to show how much stress your body is experiencing, or how much it’s recovered. The key number it uses is the exact time in between heartbeats, or what it calls RR intervals or interbeat intervals.
In my experience, my data seems to align with what the science says: When my own physical activity has dropped off for a time frame and I am less healthy overall, my HRV is lower. My morning readiness score is usually lower on mornings when I haven’t gotten enough sleep, and my stress levels definitely affect it.
However, by virtue of being technology, it has its flaws. I got a series of very bizarre readings in October and eventually determined that the problem was caused by a low battery in the chest strap — but before I came to that conclusion, I was somewhat convinced that my heart was on the verge of imploding.
On the other hand, I love to see the heart rate data the chest strap allows me to collect during workouts. One problem with wrist devices, such as the Apple Watch and Fitbit, is that the heart rate readings during exercise can get thrown way off when your arms are moving in multiple directions — they may stay steady during a run, for instance, but oftentimes, aerobics or weightlifting can render them practically useless. The chest strap is far more accurate.
Elite athletes — which I am most certainly not — may look at the data to know when to take a step back from training. In my case, it’s the inverse: sometimes my morning reading shows that my HRV is relatively low when I haven’t exercised for a while. It’s been a good indicator to me that I need to go work out, which helps me relieve some stress and tension, and generally my reading is better the next day.
About Healthy Outlook
Healthy Outlook is a column written by Journal-World reporter and Health section editor Mackenzie Clark, in hopes of helping readers make their lives a little bit happier, healthier and more active.
Have questions about the world of health and wellness in Lawrence, or a health story idea? Contact Mackenzie:
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