Heart rate variability (HRV) is simply the measurement of variation between each heartbeat.
Heart rate variability manifests as a function of your heart rate, but it actually originates from your nervous system- Specifically, your automatic nervous system (ANS). Your ANS controls involuntary aspects of your physiology (digestion, breathing, heart beat, blood pressure, etc.), and has two divisions: the parasympathetic nervous system (PNS) and the sympathetic nervous system (SNS).
The parasympathetic branch is known as the "rest and digest" response and inhibits the body from overworking and restores the body to a calm and composed state. Thus, the PNS slows your heart rate.
The sympathetic branch is associated with the "fight or flight" response and reacts to things like stress and exercise. Thus, the SNS increases your heart rate.
Heart rate variability comes from these two competing ANS branches. One telling the nervous system to speed up heart rate and one to slow down. This fluctuation is called the HRV.
Having a high HRV, means that your body is responsive to BOTH sets of inputs (PNS and SNS.) This is a sign that your nervous system is balanced, and that your body is capable of adapting to its environment. It is a sign of resilience and behavioral flexibility.
Some fitness devices (such as the Oura ring, WHOOP, and Fitbit Sense) track HRV. There are questions about the accuracy of these tracking tools, however I encourage you to look at the data in a different way.
If you use the same device and monitor the same data over time, you can observe your trends. These trends can be connected to your lifestyle behaviors such as sleep, stress, nutrition, hydration, recovery, and exercise to see how they are affecting your nervous system and your overall well-being.
Knowledge is power.
HRV can be used as another preventative tool and help you on the path to the best version of yourself.
Read more about HRV below.