ECG explained: The science behind the wearable health tech revolution

What you need to know about technology for serious health tracking
ECG wearables: The state of play
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Heart rate monitors are part and parcel of smartwatches and fitness trackers now, but electrocardiogram (ECG) is the new key sensor in town. Apple threw ECG into the spotlight with the launch of the Apple Watch Series 4 and it's starting to find its way into other smartwatches too. But what is it, and why do we need it?

We're going to break down how ECG works, why it's considered more reliable, and how companies like Apple will seek to use it.

Wareable verdict: How to use the Apple Watch ECG feature

Plus, we'll tell you about the wearables that already offer ECG tech on the wrist and other parts of the body.

ECG and heart rate monitoring

Optical heart rate sensors are good for producing information like on-the-spot readings or resting heart rate data, which can be a good indication of you current state of health. They're pretty useful for adding HR data when you're working out, too.

Generally, all of these heart rate monitors are based on the same technology. We're talking light-based optical tech (PPG) that uses flashing LEDs which penetrate the skin to detect blood flow. The light reflected off that blood flow is captured by those sensors and with algorithm smarts produce the heart rate data. It's a non-invasive way to measure heart rate and that's why a lot of companies use it in their wearables.

But optical heart rate sensors have an accuracy problem, and we've known that for a while. They're getting better, but they still have issues at high intensity and keeping up with the likes of interval training. A variety of things can impact on readings including skin tone, skin temperature or simply making sure the heart rate monitoring wearable is worn securely enough to produce reliable data.

ECG explained

Those three letters above stand for electrocardiogram and, as mentioned, it's a term you'd more commonly hear in the medical industry. You might also hear it referred to as EKG, which means exactly the same thing. It refers to a medical test carried out with a electrocardiograph that's used to detect any cardiac abnormalities.

How does it do that? An electrocardiograph usually requires placing multiple electrodes on the skin situated close to the heart that measures electrical activity produced by the heart as is contracts. This electrical activity is then sent to a receiver that records the information, and this is where the heart's rhythm can be analysed and irregularities can be detected.

The benefits of ECG wearables

ECG heart rate monitoring wearables: The story so far

Improved accuracy

The obvious one is that it's a more accurate method to measure that electrical activity from the heart. You don't have to be plastered with all of those electrodes on your body to do it, either.

Take a chest strap that uses ECG tech, for instance. While many people aren't fans of wearing them, they do concentrate placement of those electrodes close to the heart to record and transmit the data.

Those electrodes will require moisture or sweat to provide a reliable connection, and it's why you are prompted to wet the electrodes a little before sticking that chest strap on.

Read this: Five ways smartwatches could break out as medical devices

Another benefit is that ECG wearables work with smartphones and other wearables (like watches), replacing the need for one of those old school receivers to collate and log the data through companion apps or third-party apps. That means you can analyse the data in the comfort of your home or wherever you need to take a reading.

Healthier insights

ECG heart rate monitors have already been embraced by wearables, but largely for fitness. In the case of chest straps for instance, it's going to give you more reliable data – particularly for high intensity training when the heart activity fluctuates. Optical sensors tend to take longer to adjust to those fluctuations.

ECG and the accuracy that comes with it also opens the door for companies to start exploring more serious health issues, specifically focused around the heart. We already know that both Fitbit and Apple intend to explore the possibility of its devices being used to manage heart health and detecting conditions like atrial fibrillation. The ability for your wearable to detect when there's a serious problem with how your heart is functioning is obviously a huge thing to be able to do without potentially needing to visit a doctor or medical professional to find this out.

Challenges of making ECG wearables

When you start talking about selling wearable devices that enable anyone to diagnose a serious medical condition, you have to be certain that the technology can be relied on. There's no doubt that companies who start exploring serious heart health monitoring realms will perform their own comprehensive testing before saying that their wearables can actually do this. They'll also have to seek approval from the appropriate regulatory bodies. So in the US, that means getting the thumbs up from the FDA.

ECG wearables available right now

Apple Watch Series 4

£399.99, Amazon |

ECG explained: Why the HR tech from the Apple Watch Series 4 is a big deal

The latest Apple Watch uses ECG, with sensors built into the ceramic heart rate monitor under the watch, and also the new Digital Crown. Open the ECG app and place your finger on the crown, and you'll get an ECG examination in 30 seconds, including a check for atrial fibrillation. And Apple has gone out and got FDA approval for its ECG, as well as clearance in the European Economic Area.

Samsung Galaxy Watch Active 2


ECG explained: The science behind the wearable health tech revolution

Samsung's refresh of its Galaxy Watch Active comes just a few months after the first version of the watch, but features a major upgrade by bringing ECG to the table. That said, Samsung has confirmed that the feature won't be active by default - it hasn't yet been approved by the FDA, for one. Samsung says it'll share more details when it's ready to be put to use.

Amazfit Verge 2

From around £115,

ECG explained: The science behind the wearable health tech revolution

Amazfit's latest and greatest, the Verge 2 was recently unveiled, boasting ECG technology to place it as a direct competitor for the Apple Watch. This works by using Huami's Huanghan No.1 always-on AI chip. This nifty chip features a cardiac biometrics engine to monitor your heart rate more accurately, including screening for heart arrhythmia and atrial fibrillation. At the moment, however, the Verge 2 is only available in China, with US and European launches planned.

Kardia Band

£199, Amazon |

fitbit atrial fibrillation trackers devices

AliveCor is a startup that's all about monitoring heart health, and has launched its KardiaBand that works with the Apple Watch. It uses electrocardiogram (ECG) technology, which detects the electrical activity produced by a heartbeat offering real-time detection of AFib. It remains the first and only medical accessory device for the Apple Watch cleared by the FDA.



fitbit atrial fibrillation trackers devices

Qardio's wearable takes the form of a chest strap and uses medical-grade ECG tech that can send live data on your heart rate, heart rate variability, respiratory rate, temperature and activity to your phone. Like AliveCor's Apple Watch strap, the QardioCore is designed as a preventative, everyday (or week) health monitoring device to be used at home in between checkups. It's currently only available to buy in Canada, Europe and Australia, as Qardio seeks approval from the FDA to ship in the US.

Hexoskin Smart


ECG heart rate monitoring wearables: The story so far

Hexoskin's new gen connected garments are equipped with ECG tech that the startup says has been clinically validated to continuously track heartbeats. The iOS and Android compatible clothing can additionally take heart rate variability measurements to offer insights into stress, training effort, training load and fatigue.

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