I learned about Heart rate Variability (HRV) when I started to investigate methods and protocols to improve recovery from exercise. This led me to study and understand sleep and the role it plays in the recovery process. One of the metrics used when monitoring sleep is your HRV. HRV has been identified as a complex measurement of the variation in time between each heartbeat. We know that having a heartbeat that is either too fast, too slow, or irregular can be a sign of a problem. Using that thought process, you may assume that a steady heartbeat with no difference between beats (which is a low HRV) is the sign of a healthy heart, but you would be incorrect.
You want to strive for a high heart rate variability, which means that there is a constant fluctuation in time between beats. Understand that this is measured in fractions of a second (milliseconds). An example is if your resting heartbeat is 60 beats per minute, instead of 1 second between beats you may have .8 seconds, then 1.2 seconds, then .9 seconds. This is not to be confused with heart arrhythmia or an irregular heartbeat. A heart arrhythmia occurs when the electrical signals that tell the heart to beat don't work properly. The heart may beat too fast or too slow or the pattern of the heartbeat may be inconsistent. A heart arrhythmia may feel like a fluttering, pounding, or racing heartbeat. Some heart arrhythmias are harmless. Others may cause life-threatening symptoms.
According to several studies, high HRV seems to signal a healthy heart, because it reflects the heart's ability to respond quickly to rapid changes occurring throughout the body. HRV reflects your autonomic nervous system rather than your heart. This primitive part of your nervous system works on autopilot, regulating your heart rate, breathing, blood pressure, and digestion. There are two parts: one governs the stress (sympathetic or fight-or-flight) response. The other controls the relaxation (parasympathetic or rest-and-recovery) response. It’s a dance amongst the two responses. You want your heart rate to have the ability to bounce between dancing like Carlton from the Fresh Prince and Patrick Swayze in Dirty Dancing.
In a healthy person, HRV should increase when your heart rate drops, as it does during relaxing activities such as reading or meditating. HRV decreases as the heart rate rises, such as when you exercise or are under stress. In fact, it changes constantly, both throughout the day and from day to day. But chronic stress, poor sleep, lack of exercise, and an unhealthy diet can disrupt the balance, and your fight-or-flight system can shift into overdrive.
This past weekend I received my second dose of the shingles vaccination. It put stress on my nervous system, and you can see the impact on my recovery from the data of my OURA ring. The first picture is the day of the vaccination, the second photo is the day after, when my nervous system started to recover.
Here’s where it can get confusing. HRV is going to vary from person to person. There is no standard HRV variable and it’s highly personalized. The reliability of devices that track HRV such as the OURA ring, Apple watch, and Fitbit have been questioned. In closing, I believe by tracking your HRV you are more probable to make better and healthier lifestyle choices. That should be the goal.