Are fitness trackers actually accurate?

A study by Stanford Medicine concluded that six out of seven fitness trackers measured heart rate accurately. In fact, they did it within 5%. However, not one of the devices in the study calculated calories accurately. For most people, the counts are pretty good, but check your step count on two different fitness trackers or compare it to your smartphone's estimate and you'll see the differences.

A study published in BMC Public Health compared four of the most popular fitness trackers (Withings Pulse, Misfit Shine, Jawbone Up24 and Fitbit Flex) for accuracy, functionality, user experience and user satisfaction. It's no wonder, then, that millions of people use some kind of fitness tracker every day and that the global market is worth billions. Euan Ashley and his team conducted a study to determine how accurately seven types of fitness trackers measure heart rate and energy expenditure. However, even WHOOP, which is considered the current gold standard of trackers, does not have any precise clinical evidence on the accuracy of energy expenditure.

Study participants used fitness trackers while walking or running on a treadmill and pedaling on an exercise bike. Despite all the possible inaccuracies, there is also plenty of evidence that fitness trackers can encourage you to be more active and help you be fitter, as long as you interact with your device and set goals that you actually work towards. Most fitness trackers do this using something called a three-axis accelerometer, a small module that detects (you guessed it) acceleration. So, although FitBit and Garmin can provide a great tool for monitoring specific activities such as walking or running, these fitness trackers are extremely imprecise.

This technology detects movement with electromagnetic sensors and takes advantage of an algorithm that teaches trackers to recognize a step. The following table shows a comparison table of the accuracy of physical activity trackers with respect to tracking different movements and steps. The functions of each type of fitness tracker are similar, but they all use different proprietary calculation algorithms, user interfaces and applications. When it comes to health and diet, for example, Gear Patrol details how studies show that people who didn't use trackers lost more weight compared to those who did.

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