How Accurate Are Fitness Trackers and Should You Rely on Them?

Fitness trackers are now part and parcel of working out for many people across the world. For example, runners can benefit from features showing them the distance they’ve ran, their heart rate, the number of calories burned and track how much sleep they’re getting, among other functions. Although these benefits are great, here on EnMotive Hub, we have also noticed some drawbacks to using these devices, like becoming too dependent on them. With more companies manufacturing fitness tracking devices, now would be an appropriate time to discuss how much we should be relying on this developing technology, specifically when it comes to running.

In an article on The Wired Runner, the author notes how overtraining is a common cause of injuries and that using a fitness tracker with heart rate monitoring can help runners be more aware of their body. The heart rate monitor can alert you if you’re pushing your body too hard to a point where it can leave you vulnerable to injury. It's worth noting that before being commercially available, heart rate monitors, came to the consumer market from professional sports. An article by The Innovation Enterprise on the impact of technology on sports, notes how heart monitoring technology can pick up abnormalities where previously issues would have gone undetected. This means that these devices monitor an athlete’s heart to see how much it strains under exercises like running. Commercial fitness trackers use that same technology to keep track of your heart health by measuring resting and active heart rates, with a lower resting rate generally an indicator of better health.

When it comes to heart rate monitoring specifically, the results from a Stanford study conclude that they are fortunately more or less accurate when it comes to measuring heart rate. In this study, 60 volunteers were given fitness tracking devices like the Apple Watch, Fitbit Surge, PulseOn, and Samsung Gear S2. The results showed that the most accurate was the Apple Watch, with only a 2% margin of error. Even the least precise device in this part of the study, the Samsung Gear S2, reported only a 6.8% deviation. Through knowing your heart rate, you will be aware of just how hard your heart is working. Over a period of time, the data can be useful to your doctor, who will be able to give you a deeper understanding of your heart health.

Tech website Tom’s Guide delves into the subject even further, expanding the comparison to include devices like the Apple Watch Series 3 & 4, the Garmin Fenix 5 and the Samsung Galaxy Watch. These devices were measured against the highly accurate, chest-worn Polar H10, which was found to be within one beat per minute of a stress test machine. From here, it was found that the Apple Watch Series 4 and the Samsung Galaxy Watch were able to catch up with the capabilities of the Polar H10 after a run. This shows great promise for heart-monitoring technology in fitness trackers, as wrist-worn devices like the Apple Watch can only become more accurate as technology advances.


Some runners also rely on fitness trackers for calorie counting and counting distance. The bad news, though, is that they can be unreliable in these aspects, and the Stanford study further corroborates this. In fact, none of the devices tested had a margin of error less than 20% for the caloric burn; on average, the lowest recorded across the pack was 27.4%, with an astounding 92.6% average margin of error for the Fitbit Surge. Runners also considering using a fitness tracker to count the distance they've ran should be warned. Many of these devices deduce how much you've ran based on steps counted or arm movement, which the Guardian’s Kate Carter claims can be wildly inaccurate. When training for a marathon, using landmarks in your area as distance markers is still a better alternative.

So, should you rely on these trackers? Relying on any developing technology requires a sense of pragmatism. A huge problem with technology today is that because it is so “smart," many of us become lazy and dependent. A big reason for this is the effect known as a “health halo,” where the health benefits of a product are greatly overestimated due to a simple claim. When it comes to health and eating, for example, Gear Patrol details how studies show that people who didn’t use trackers lost more weight compared to those who did. While this has to do more about human psychology, rather than the technological functions of the device, it can falsely lead users to believe it’s ok to eat more as a reward for burning X number of calories and vice versa. Despite these flaws, however, functions like heart-monitoring look to be quite accurate when compared to a chest strap. Moreover, fitness trackers offer more features and functions than just a heart rate monitor, which can give runners a better understanding and awareness of their overall health.

Written by: Allison Harp