Heart Rate Variability: A Jack-of-All-Trades Guide

Heart Rate Variability Is A Unique Index, Yet To Unlock Its Full Potential – You Need To Be Aware Of Quite A Lot Of Details And Nuances.

It is a well-established truth that the prevention of the illness – the notion of prophylaxis – is far easier to complete than the actual treatment. In other words, prevention is crucial due to being statistically way more effective at the survival rates and quality of life of patients – and, simultaneously, being more economically efficient – after all, it is way cheaper and simpler to screen than to treat.

Individual Prophylaxis…

There are different kinds of prophylaxis. Mainly it is divided into primary, secondary, and tertiary, but there are also subdivisions of medical vs. non-medical prevention and state vs. collective vs. individual prevention. The latter one – individual prophylaxis – is of utmost importance – ultimately, it is in your best interest to care for yourself.

Yet individual prophylaxis does not only mean getting regular screening procedures like colonoscopies or EGDper, forming ordinary hygiene acts like washing and teeth brushing, or checking normal pulse rate and target heart rate. The most important aspect of your disease prevention is to lead a healthy lifestyle, including getting quality sleep, having proper exercise time, being constantly nutrition, including all kinds of vitamins and essential microelements, etc.

…and Heart Rate Variability

To accompany a healthy routine, more and more people are beginning to use special health-tracking apps that record their progress and often provide helpful advice. Such apps are commonly using an innovative indicator called Heart Rate Variability (HRV). Yet, despite this, the user base remains generally ignorant about HRV, heart rate variability, heart rate definition, good heart rate variability, the technology behind it, how it works, and all the other related subtleties. So, let’s try to fix it, shall we?

To begin with, let me advance you to this masterfully done in-depth article, written and edited by specialists in the field. It takes quite some time to read into, indeed, but the read itself is very informative at describing HRV. Herein, I will try my best to explain the most important points and aspects that concern the public as briefly as it gets. Additionally, I will shed some light on some questions regarding other cardiovascular indices and devices and appliances needed for quality HRV measuring. So, let’s have the show on the road.

The Basics of Heart Rate Variability

The information in this section is not rocket science yet is crucial in the strong understanding of this indicator.

What Is HRV?

Heart Rate Variability is a physiological phenomenon of the difference in times between heartbeats. To simplify – it is an indicator that reflects the unevenness of your heartbeat. Naturally, the heart is not a perfect metronome, and every interval differs from the other one. It is indistinguishably to human senses, but observably enough to be recorded with relatively simple machinery.

What Causes It?

Here, a slight detour into physiology should be made.

Though the heart is able to generate contractive impulses autonomously while fully isolated, in vivo, it is always controlled by the autonomic nervous system, precisely – by the pair of its antagonistic branches – sympathetic and parasympathetic. The sympathetic branch mediates the “fight or flight” response to the potential dangers, while the parasympathetic branch is responsible for the “rest and digest” behavior.

Both branches are perpetually “in a struggle” to control bodily functions, and their power – tonus – depends on the surroundings. During stress or danger, the sympathetic system prevails, increasing the average heart rate, consequently decreasing the HRV. Vice versa – when the threat disappears, the parasympathetic system takes the lead, slowing the heart to its resting heart rate and increasing HRV.

What Is a Good Heart Rate Variability?

As you may have already understood from the previous article, the rule of thumb for HRV is “the higher, the better.” Unfortunately, though, the HRV is yet to come to a “one fits all” type of standards like the resting heart rate (in case you forgot what a good resting heart rate is – it’s 60-80 BPM). For example, the typical value of the SDNN measure is calculated to be 141±39 ms, which is purely inapplicable right now, especially considering the enormous standard deviation.

Therefore, your ideal HRV is the one you are most often experiencing during calm, peaceful moments of your life. Undoubtedly, once you extract these numbers after a couple of weeks accompanied by HRV measurement, you should take a note of them.

How to Measure Heart Rate Variability?

To begin tracking your HRV, you have to download designated apps to have them plow through the field of computing work and gather the cardiovascular readings with the help of specialized heart rate monitors. For iPhone or alternative smartphones, you can even collect the data with the help of an inbuilt camera, using the technology called Photoplethysmography (PPG).

The Instruments of Measurement

Considering that having a healthy lifestyle is literally one of the most significant factors preventing strokes and heart attacks, it is essential to trust your HRV values fully. As such, you need to use quality equipment and software – or, at least, be able to differentiate one from the other.

Ergo, in this section, I want to shortly describe the markets of both: the software and hardware, their peculiarities, and nuances. This information, I firmly believe, will be priceless once you need to make a conscious choice.

The Hardware

What matters is the hardware section is how the data is collected. There are three main ways: strictly hierarchy, with the quality of data gathered being usually inversely related to the device’s convenience. Let’s disassemble this premise, starting with most convenient to least convenient.

Smartphone Photoplethysmography

The paramount convenience of this technology is born of the fact that it requires no purchase of any gadget – just a smartphone, which everyone nowadays owns and a piece of software that supports this tech, like, for example, Welltory. Rationally, smartphone PPG is an excellent way to try the idea for the first time without spending any cash.

With the help of sophisticated algorithms, the smartphone camera detects the changes in the blood volume in the microvasculature of the soft tissues by analyzing the shift in the color saturation of the image. Increased red color saturation corresponds with the heartbeat that just happened, and as such, the data is extrapolated into heart rhythm.

Conveniently enough, even blood pressure can be measured with the help of PPG, though the blood pressure and heart rate app are still required to process the results. While we are here, let’s get a short detour and quickly remind ourselves about the basics of blood pressure as well, shall we?

What Is Blood Pressure?

Blood pressure is essentially the force that the bloodstream applies upon the walls of blood vessels. It is born of a variety of factors, including the strength of heart contraction, the diameter of the vessels, the overall muscular tonus of its walls, and the viscosity of the blood.

What Is Normal Blood Pressure?

The normal resting blood pressure values are less than 120/80 mmHg.

Why Are There Two Blood Pressure Numbers?

The first number means systolic pressure (during heart contraction), and the second number – diastolic pressure (during heart rest).

How to lLwer Blood Pressure?

The primary advice for patients with idiopathic hypertension is to alter their lifestyle to be healthier, limiting the salt’s casual consumption. Should this not help, the physicians prescribe the hypotensive drugs. Their intake should be precisely in prescribed doses. Else what causes low blood pressure can lead to hypotensive crisis.

Alright, We Are Back on HRV-Track

For such convenience, a user pays with accuracy. The algorithms require, for example, a clear visualization, the quality of which fluctuates due to a plentiful number of variables that can influence it. These include the inherent resolution and frames per second of the camera, the surrounding conditions like the brightness and ambient light levels, the placement of the finger, and its movement during the capture.

Optical Heart Rate Trackers

There is an inherent dichotomy among the optical heart rate trackers. They are either integrated into fitness watches (and thus wrist-based) or standalone arm-based. The knowledge of any heart rate variability monitor would not hurt, though.

Watch-Based HR Trackers

The smart- and fitness-watches are equipped with such trackers almost universally, like smartphones – with a back camera. Undeniably then, that this method of collecting cardiovascular data is the most popular.

A sonar-like technology is using to collect these heart readings. First, a LED sends frequent beams of green light waves into the soft tissue, and then the differences in light refraction are evaluated. The more blood, the less light is fully reflected – and reflected light is caught by the photoelement.

Since such heart rate trackers are extremely comfortable while worn, they are good at constant 24/7 monitoring. In addition to that, they are relatively accurate, though not without the ceiling.

The inherent limitations of this method are that dirt and sweat annoyingly tend to disrupt the truthfulness of the readings. At the same time, there is not much subcutaneous soft tissue in the wrist area to begin with, which further decreases the integrity of the data.

Arm-Based Optical HR Trackers

Essentially, such a good heart rate and stress monitor operates within the same bounds as its integrated sibling. Thanks to the upgrade in the localization – now attached around the arm – more accurate readings are offered, mainly due to the increase in the volume of soft vascularized tissue and less sweat produced.

Said HR trackers are, quite unfortunately, undeservedly unpopular – the jack-of-all-trades fitness watches dominate the market and push them aside.

Chest Heart Rate Monitors

The chest heart rate monitors use specialized sensors to detect the electrical potential of the myocardium to draw the heart rate. Rationally, it is a portable ECG device. Such readings can be altered only by the heart stimulator – or powerful magnetic field – so the data produced by the gadget is highly accurate.

Au contraire, the body location of chest HR monitors can be an issue for some users, as well as required regular maintenance after each use. Needless to say, these devices are also costly. Overall, this makes them perfect for professional athletes, but amateurs need to think twice.

The Software

It can be tough to choose one app to check heart rate among the humongous supply. The helpful tip is that there are two main pillars: functionality and user interface. For example, some apps may offer unprecedented blood pressure charts, help you analyze normal blood oxygen levels, and then advise on how to increase the blood oxygen level. But do you really need a blood oxygen level app with a clogged interface, after all?

Contrarily, there are apps with nice and clean and tidy user interfaces, such as Welltory. No – I got the analogy wrong because Welltory offers both: the user-friendliest interface as well as deep and thorough analytics, advice, and conclusions. Just try it out – the app is free for beginners!

In Conclusion

I hope this guide was helpful enough and helped you fill in blank spaces in your grasp of technology basics. Though there is still quite a lot to learn, this was – or should have been, at least – a decent headstart.

Bear in mind, though – no software algorithms can be a decent substitute for the professional doctor. Should you feel unwell or your cardiovascular measurements constantly be in the “unhealthy” range, do not hesitate to contact your physician.