What is HRV and why does it matter?
Many of us wear fitness tracking devices, whether we know it or not. Your smartwatch, be it an iWatch, Garmin, or Fitbit, are just a few I can name that can track all sorts of health and fitness data from heart rate, to step count, to calories burned; they do it all. One of these measurements you might not be as familiar with is Heart Rate Variability (HRV). It seems like everywhere you turn now, people are talking about HRV and why you should care about it.
I'm going to do my best to explain what this is and why it's important in layman's terms.
HRV is the variability between heart beats. For example, at rest, let's say your heart beats 60 bpm. Those beats are not always happening on the second, every second. Some beats are at 0.9 sec between beats and others at 1.1 sec between beats. So it's the variability between your heart beats that HRV is measuring- does that make sense? I hope so!
In order to understand why your HRV measurement may be important you need to be familiar with how our autonomic nervous system (ANS) works. This is the system that regulates our sympathetic nervous system (often referred to as "flight or fight"- in a car analogy lets say the gas pedal- this increases heart rate and blood pressure), and our parasympathetic nervous system (often referred to as "rest and digest"- the brake pedal, this decreases our heart rate). Our body is in constant flux being pulled between these two systems and they are both beneficial in specific circumstances so one is not "better" than the other. It's this tug between the two of these physiological states that creates the variability between our heart beats. You want to have variability because it means not one system is always driving the car, they are sharing the burden of running your system.
What can tend to happen is we end up hanging out in the sympathetic system too much and that can drive our heart rate higher and our beats are much more fixed with less variability between them. This can be good, like when we exercise, or need to be super focused, some degree of stress is healthy for balance. The problem arises when we can't shift from this sympathetic "tone" (as it's often referred to), back to parasympathetic "tone" and relax. Healthy fluctuation in HRV occurs when both of these systems are "fighting" each other to control our heart rate. This is the ideal situation and when our HRV measurement will be higher and healthy.
As mentioned above, when our variability plummets, we are usually stuck in the sympathetic nervous system and it's running the show, not allowing the parasympathetic system to battle for control, and therefore our heart rate is quite static and rhythmic without the variability we should be having if it were more balanced between the two systems.
Ok, I know, this is A LOT of sciency stuff- but hear me out, I'm about to tell you WHY you need to care about this. Having a higher HRV means your body is responsive to both sets of inputs (sympathetic and parasympathetic) and means your nervous system is balanced and this equates to being more recovered and ready for action. Your body is more robust and adaptable when your HRV is higher.
Here is the list of things that can affect you HRV:
Exercise volume and intensity
Rest and recovery from workouts
Chronic health conditions
Sleep habits and quality of sleep
Diet (and alcohol)
Age and gender
Lower HRV is commonly attributed to stress, the "not so good" kind. The unseemly cast of characters that primarily cause this are life stressors, poor sleep, poor nutrition and either lack of movement OR overtraining. It is true that if you work out really hard your HRV may take a dive for a few days, this tells you NOT to train super hard until your HRV starts to rebound meaning you are recovered enough to push your body really hard again. Of course the only way to know this would be to have a consistent string of data, so measuring your HRV daily is in your best interest to develop a pattern.
Comparing your HRV to someone else's is like comparing apples to oranges. The most important metric is having reliable daily data on yourself, and watch for drops in the HRV in your own numbers. Typically athletes, younger people, and men have higher HRV's then their counterparts- but genetics plays a role here too. If you log your daily HRV and also keep a journal of what you did that day/week/month- how much/hard you exercised, what you ate, how well you slept, this would provide a perfect blueprint for assessing any change in your HRV (either up or down) to try to figure out why your numbers have changed.
Many of the wearables will track your HRV without you even doing anything, but it isn't a bad idea to do a 2 min HRV assessment each morning to get a consistent snapshot of your HRV at relatively the same time in the same conditions each day. If you have a heart rate monitor this is fairly easy to do. Click this link to watch a quick video about how to check your HRV using a Polar HR monitor and Elite HRV app. If you wear an Apple Watch you can force your watch to take your HRV by opening the Breath app and taking a reading by doing the breath work for 1-3 minutes. Then open your Health app and check out your HRV score there. Whoop and Aura are fancy devices that use complex algorithms based on your sleep cycle, heart rate and other biometrics to measure your HRV and give you a readiness score.
You do have to use some sort of device to measure your HRV but a simple polar strap and free app would be your cheapest option of those listed above. I hope I was able to shed some light on this mysterious metric, it can be a very beneficital tool in your health and wellness toolbox if used consistently to guide your training and lifestyle choices.