Recent research from Mintel reveals around 4 million fitness watches and bands were sold in the UK in 2017.1 These devices can monitor a number of aspects of your health: from sleep patterns and eating habits to how quickly your heart beats when exercising. But just how reliable are they when it comes to establishing the health of your heart? To help clear this up, we’ve put together this guide on understanding whether fitness watches are an accurate representation of your heart health.
What is a healthy heart rate?
A normal and healthy resting heart rate (when you are in a state of physical and mental relaxation) is around 60-100 bpm, but this can vary from person to person. A number of health and lifestyle factors such as stress, obesity or caffeine, for example, can all cause your heart rate to fluctuate beyond the healthy range.2 Genetics play a big part, too. Even someone who leads a relatively active lifestyle can be left with a very low or very high resting heart rate. As such, there is a very large spectrum of what constitutes a normal heart rate which is determined by a whole range of factors.
How accurate are fitness watches for measuring heart health?
Whether you have a healthy heart, or have been diagnosed with a specific condition, it’s always a good idea to keep an eye on your heart health. With many fitness watches housing features that claim to measure heart rates, it's easy to believe that they provide an accurate picture of how healthy our hearts are, and spot signs of abnormalities. In recent years, there have been a range of studies questioning the accuracy and usefulness of fitness watches in measuring heart health. In 2016, one major watch brand was taken to court after research from California State Polytechnic University found that their heart monitor fitness watch devices “do not and cannot consistently and accurately record wearers’ heart rates”, despite the company's claim that the devices could.10 The study found the devices read on average 9 beats per minute (bmp) less than the wearers’ actual heart rate but could be as much as 23 bpm out – concluding the devices were “highly inaccurate”.
However, as the technology of fitness watches develops, there is evidence to suggest that newer models may be able to detect potentially fatal health conditions. Currently, there are a number of fitness watch prototypes being developed by experts that record blood pressure and heart rate variability, although these are still recommended for use in conjunction with medical expert help.3 A 2017 study found that two brand of fitness tracking devices were almost as accurate as a medical electrocardiogram (ECG) in detecting heart rate abnormalities like arrhythmias — that is, when your heart beats with an irregular rhythm or speed.4 However, the same study also found that fitness watches were less able to identify tachycardia, an abnormally fast heart rate. As such, more research is required in this area to be able to safely rely on these trackers to give an accurate representation of heart health.
Relying solely on yourself to monitor and interpret your heart rate without the help of a medical professional can be an easy way to get an inaccurate perception of your heart health. Many experts continue to suggest that if you do monitor your heart rate on your fitness watch you also check your pulse the old-fashioned way — on your wrist — and use your own information alongside your device’s data to pinpoint anything that seems irregular for you.5
The benefits of fitness trackers on heart health
While there may not be definitive evidence either way to suggest the complete reliability of fitness trackers to monitor heart health, they may still be beneficial in maintaining and supporting an overall healthy heart. Significantly, fitness watches don’t just record heart rate, they can also monitor the number of steps you take, the distances you cover and the amount of time you spend exercising. For this reason, The British Heart Foundation states fitness trackers are beneficial because these features can help users to monitor their physical activity over time, ultimately encouraging them to stick to their exercise routine in order to see their long-term progression. However, they also advise that, “if a medical professional has advised you to keep track of your heart rate, talk to your doctor to make sure you choose a suitable device.”6
Fitness trackers can establish how much water you drink on a daily basis, as well as encouraging users to input their daily food intake via an app on your phone. Since the heart is a muscle, it requires the same amount of hydration as every other part of our body in order to be able to pump blood efficiently around the body. Staying well hydrated means your heart doesn’t have to work so hard to keep the blood pumping through the blood vessels to the muscles. In 2016, one study found that even being mildly dehydrated can affect vascular health as much as smoking a cigarette.7 Logging how much and what you eat can make you more mindful of the foods you are using to fuel your body, encouraging you to eat a more heart-healthy diet.8 What’s more, sticking to a balanced diet means maintaining a healthy weight reducing the risk of heart and circulatory conditions such as high blood pressure and high cholesterol.9 As such, even without monitoring your heart rate, fitness watched can support you in taking significant steps towards reducing your risk of heart disease.
1Mintel Press Team (2017), Sales of fitness bands and watches, Mintel
2Robert H. Shmerling, MD (2017). How’s your heart rate and why it matters?, Harvard University
3Adrian Courage (2017). The health watch that can help get the first signs of heart disease, Map Health Watch
4Anoop Ninan Koshy, Jithin Sajeev, Mark Zureik, Maryann Street, Michael C. Wong, Louise Roberts and Andrew W. Teh (2017). The accuracy of smart watches in arrhythmias, The Journal of American Cardiology
5NHS Guidelines (2018). How do I check my pulse?, NHS
6The British Heart Foundation (2017). Fitness Trackers, BHF
7Giannis Arnaoutis, Stavros A. Kavouras, Nikolaos Stratakis, Marita Likka, Asimina Mitrakou, Christos Papamichael, Labros S. Sidossis Kimon Stamatelopoulos (2017). The effect of hypohydration on endothelial function in young healthy adults, Journal of Nutrition
8Heart UK (2016). Cholesterol and Diet, Heart UK
9Heart Foundation (2016). Healthy Weight, Heart Foundation
10Edward Jo, PhD and Brett A. Dolezal, PhD (2016). Validation of the Fitbit® Surge™ and Charge HR™ Fitness Trackers, Lieff Cabraser Hemann & Bernstein, LLP