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Heart rate variance: The most important health metric you didn't know about
Summary
While we all know about heart rates and calorie burns, there is one key health metric that is more difficult to access. We talk about Heart Rate Variance and why it is important
It’s always a good idea to get your step-count in every day, and to check your heart-rate and how many calories you have burnt per workout. These are the standard fitness metrics that have gained popularity over the last few years, and most active people use these parameters. But one metric which has gone under is heart-rate variability (HRV).
There are two reasons for this. One is that it’s not always easy to measure without going to a clinic for a checkup. And the other is that while you can access this data on certain fitness wearables, it is buried under a lot of other information, and therefore not particularly easy to find.
“HRV is simply a measure of the variation in time between each heartbeat. This variation is controlled by a primitive part of the nervous system called the autonomic nervous system (ANS). It works behind the scenes, automatically regulating our heart rate, blood pressure, breathing, and digestion among other key tasks," states a Harvard Healtharticle titled, Heart Rate Variability: How It Might Indicate Well-Being.
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Heart rate is the number of times the heart beats in a minute, but variance is measured in milliseconds because that is the space between two beats. This can vary according to age, fitness, and the sleep-wake cycle. “HRV metrics change as you grow older but a ballpark healthy HRV would be 20-70 milliseconds. It would depend on your fitness. But one must take into consideration other factors as well. It will change if you’re anxious, nervous, or in a very high stimulation setting for longer periods of time, and also your sleep patterns," says Dr. Sagar Shah, who is a cardiologist currently in Tokyo for a fellowship to learn additional structural intervention. The 34-year-old has played tennis most of his life and hits the gym five times a week, and keeps a close track of metrics such as HRV.
The most interesting part about HRV is that it doesn’t just give you a marker of your physical fitness, but your overall wellbeing. A higher HRV can mean higher resilience to stress. So, while physical activity is the obvious booster for a better HRV, other practices like meditation and habits that aid better sleep will also help.
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One thing to remember is that heart rate and HRV have an inverse correlation. The heart rate is mostly low when the body is in a resting state and high when it’s doing physical activity. But a high HRV during rest and low levels during activity is equal to a healthier body.
The thing that marvels me the most about HRV is how it is related to the body’s response mechanism. The autonomic nervous system is divided into two parts: the parasympathetic and the sympathetic nervous system. While the former’s job is to decrease the heart rate for the body’s resting state functions, the latter keeps the body ready to spring into its fight-or-flight response.
“High-resting HRV means your ANS is working efficiently and can trigger the exact response you require from your body as soon as you need it," says a post on the popular Ultrahuman blog titled, Why Is Heart Rate Variability After All Important? It adds that HRV can drop in response to strenuous activity, and rise after recovery. “This way, HRV can indicate when you should rest and when you can start pushing yourself again. With successive exercise and recovery sessions, the athletic performance and baseline HRV of a person can increase, building stamina and endurance."
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Shah says that people might be obsessed with heart rate numbers, but it might also be because accessing HRV numbers regularly is difficult. “Finding out your HRV is not an invasive process. And while it might be easy to measure, a single finding is not useful. Keeping track of it during different activities including when resting is important."
A chest strap is the best way to keep track of HRV in terms of accuracy but popular wrist wearables have now started including it. The Apple Watch, most Garmins, the Whoop band, Fitbits and Samsung watches all have HRV options and it is time you turned it on.
