Just How Accurate is Your Fitness Tracker?? (Part 2)

In last week’s blog post (You can find that here: Just How Accurate Is Your Fitness Tracker?? (Part 1)) we looked at the accuracy of fitness trackers based on a study from 2016. And while we found out that they weren’t all too accurate, we learned that they we accurate “enough.” In this week’s post I want to look at a slightly more recent study – published in 2017, that found that fitness trackers were pretty good at measuring heart rate and not soooooo good at measuring calories burned (bummer).

Stanford University School of Medicine evaluated 7 (wrist-worn) fitness trackers amongst a group of 60 volunteers showed that 6 of the 7 of devices measured heart rate within an error rate of less than 5%. The team evaluated the Apple Watch, Basis Peak, Fitbit Surge, Microsoft Band, Mio Alpha 2, PulseOn, and Samsung Gear S2. Some devices were more accurate than others, and factors such as skin color and body mass index affected the measurements.


The 60 volunteers, including 31 women and 29 men, wore the seven devices while walking or running on treadmills or using stationary bicycles and each volunteer’s heart rate and metabolic rate was measured. For heart rate, researchers compared the fitness trackers to findings from an electrocardiogram, or EKG. Based on the study, it was seen that the devices were pretty damn accurate with most devices only being off by about 5% (not too shabby if you ask me). For calories burned, researchers compared the findings of the fitness trackers to a sophisticated system of calculating metabolism which measures oxygen and carbon dioxide in people’s breath. When it came to measuring how many calories a person burned, the findings were WAY OFF, showing inaccuracies that ranged anywhere from 20% to 93%  (which means that the worst-performing devices were wrong 93% of the time).

The overall take-home message from this study is clear – a user can pretty much rely on a fitness tracker’s heart rate measurements buuuttttt basing the number of doughnuts you just “earned” on the calories burned after a run on the treadmill is probably not the best idea (womp womp).

** If you want to know more about fitness trackers as well as reviews and advice on which fitness tracker is best for you and your goals check out: http://www.reviews.com/fitness-tracker/

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