Ever wondered how stressed you are? Heart Rate Variability (HRV) is one practical way to objectively quantify your stress and health. While some amount of stress can be good, being in a constant, long-term state of stress can be very bad for our bodies and minds. HRV helps you objectively understand the state of your body and what factors trigger a stress response in you.
As a long-time biohacker and self-tracker, HRV has become one of my favorite biomarkers to track. It allows me to understand my overall state of stress on a day-to-day scale as well as contextualize what’s affecting my stress. It’s even something I can improve.
Quite simply: By measuring your HRV and capturing contextual factors like sleep, exercise, lifestyle stress, drinking, etc. you can understand your physiological stress.
What is Heart Rate Variability? Unlike Heart Rate (HR), which is the average number of beats of your heart in a minute, HRV is measuring the variance of intervals between heart beats. You can then use your calculated HRV to know if your heart rate is showing higher or lower variability in the moment and in comparison to your baseline average (typically last 7 days). Somewhat counterintuitively, lower variability is a sign of an increase in stress and activation of your sympathetic nervous system, and higher variability is a sign of being a state of rest and activation of your parasympathetic nervous system.
Your body is a complex system, and it deploys a number of systems to keep you alive and responds to its environment and internal states. Its goal is homeostasis or a kind of living balance. In order to maintain homeostasis and stay alive, your body responds to different situations through its different cells, organs, and organ systems. One of the most important is your nervous system, which transmits to different parts of the body to control actions.
In terms of the science that backs up HRV as a valuable biomarker it all comes down to how HRV acts as a proxy to a subset of your nervous system called Automatic Nervous System (ANS) and its two main branches, the Sympathetic Nervous System (SNS) and Parasympathetic Nervous System (PSNS). In order to better understand HRV and how stress works, we need to understand how HRV relates to your ANS.
In this post, which is a continuation of a previous post on HRV as a biomarker and how to track your HRV, we will be looking at Heart Rate Variability from a more scientific angle. Specifically, in order to understand our HRV scores and what factors affect our HRV, we need to understand how our nervous system acts through these two different subsystems. One of the main reasons HRV is such a key health indicator or biomarker is its ability non-invasively to tell us about the state of our automatic nervous system. For example, are we in a state of so-called “rest and digest” or in a mode of “fight or flight”?
Let’s dig in.