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What is heart rate variability (HRV) and why it matters

Heart rate variability is one of the least understandable metrics tracked by fitness bracelets. However, it is also one of the most useful and important metrics when it comes to monitoring your recovery and overall health. So what is heart rate variability and why is it rather important?


HRV - The Basics

Heart rate variability (HRV) can be difficult because it may seem unintuitive.We used to think that a stable heart rate is a good thing.However, heart rate variability seems to say the opposite.The greater the variability of your heart rate, the healthier you are!What is happening here?To understand heart rate variability, we must first understand the parasympathetic tone.Don't worry, it's not as confusing as it sounds.


ANS - Autonomic Nervous System

Your autonomic nervous system (ANS) is part of your nervous system that controls everything that happens "automatically" (except for reflexes and some other functions, but this generalization usually applies). So your ANS is in charge of things like breathing, digestion, pupillary response, urination and of course heart rate.


ANS can be further divided into two branches. They are technically referred to as the "sympathetic nervous system" and the "parasympathetic nervous system". The easiest way to remember them is: "fight or run" and "rest and spend." In short, your body has two modes. During a fight or flight reaction, your heart rate increases, your pupils dilate, your muscles contract, and you begin to breathe hard. Your thoughts will be racing and functions like digestion and the immune response will be somewhat suppressed. The viscosity of the blood increases to increase the likelihood of clotting in the event of an injury.


Imagine facing a wild animal who wants to prey on you in the wilderness. Your body will start and prepare you for survival. Things like digestion are not a priority now! On the contrary, a state of rest and digestion starts when you are fully relaxed. This is the state we are in after a big meal (called a "postprandial state") and after a good workout. Bodybuilders refer to this condition as anabolic. During rest and digestion, we are in charge of the parasympathetic nervous system. This means you can focus on relaxing, repairing tissue, replenishing fuel in your muscles and absorbing nutrients. Muscle tone relaxes, thoughts stop racing and your heart rate calms down.



The exact amount of parasympatetic or sympatetic dominance is constantly fluctuating

The key thing to understand is that these two states are not mutually exclusive binary files.We do not "switch" between two contrasting states, such as flickering a light switch.Instead, we are always somewhere in the spectrum.The exact amount of parasympathetic or sympathetic dominance is constantly fluctuating.


We become more when we see light, for example. On the contrary, we are more parasympathetic when it is warm. And when our phone rings, we become more sympathetic as well. The crucial thing is that when we inhale we become a little more sympathetic. Every breath inside increases our heart rate to give the muscles more oxygen. When we exhale, a parasympathetic reaction occurs and our heart rhythm decreases slightly. The extent to which this happens depends on countless other factors that also affect our likeable tone. So if you are very stressed, exhaling will only slightly reduce your resting heart rate.


High heart rate variability means that your heart rate increases and decreases with each inhale and exhale. This in turn suggests that you are not extremely stressed, which would keep you in a parasympathetic state. Thus: greater variability = balance.



Accidents and illness occur when you continue to train despite what the figures tell you



Overtraining or stiffness occurs when an athlete ignores the signs of excessive tugging and continues training.Many athletes believe that weakness or poor performance signals the need for even harder training. So they keep pushing. This further decomposes the body.


One of the main reasons why your smart watch measures your HRV is to indicate recovery levels. The recovery process is actually a stressful factor for the body.T his is why our heart rate increases when we are drunk, even though alcohol is depressed. The same goes for excessive fatigue (many symptoms of lack of sleep are actually just examples of a reaction to a fight or flight), illness, or burnout.


If you train again before you are ready, you accumulate damage in addition to the damage. This is what can eventually lead to "overtraining". As your immune system spends more and more time in a suppressed state, you are becoming more and more likely to become ill. Therefore, the ideal way to train is to wait until your heart rate variability returns to normal before heading back to the gym. That's why many fitness trackers now display metrics in their respective applications. Others obscure the data and provide a more general "readiness score," but it's the same.


Remember: everything from your current stress level to a cup of coffee (aka stress in a cup) can acutely affect your heart rate variability. So the most reliable way to measure this is to measure the average for the whole day, or better yet, to record the first thing in the morning. If you want the most useful HRV data, don't forget to wear your fitness tracker overnight!

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