Do you track your calories and activity? A lot of people seem to be wearing those fitness trackers.
Have you ever wondered how accurate they really are? Iowa State University just released its latest testing results of four popular commercial fitness monitors: Fitbit Flex, Nike+Fuelband SE, Jawbone UP24 and Misfit Shine.
This poster conflicts with our own scientific studies of accuracy, so we contacted the authors to learn more about what they did. We found numerous methodological problems that we believe skewed the data. We feel that this poster, which presents data from a manuscript that has not yet been published, on a very limited sample of device (n=1), unrepresentative of our devices in general, and including concerning methodology, serves only to misrepresent our product and its performance. We have asked other independent researchers to test our devices and demonstrate its performance, and this data will be released after it has been thoroughly vetted including by acceptance to a peer-reviewed publication.
One of the most concerning things we learned is that all of their claims are based on just one Misfit Shine that from their description would lead us to believe was damaged. (A strength of our device is its long battery life – users can use a Misfit Shine for four to six months being highly active without needing to recharge it – but an author of this study revealed that they had to change the battery every week or two during the study. This is a sign that the one device they used through the entire study wasn’t operating normally.)
We learned that they used total daily calories reported by our device to infer the calories burned through activity but did not measure the calories for that activity directly using our device. Moreover, the conditions in this experiment were artificial; people were asked to do specific activities or break from activity for just short periods of time; they’re not reflective of the real world, long term conditions our device is designed to measure. Despite all of these problems, it’s worth noting that in the portion of their experiment that is most reflective of how we spend most of our day (activities of daily living and office work), Misfit actually performed among the best of the devices tested. It is possible that during the highest intensity aerobic activities, the one damaged device they used was most sensitive to motion artifacts and resulted in the skewed and unrepresentative data they are reporting.
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If the authors had contacted us during their study, we could have instructed them on how to use the devices properly, how to install the battery, and provided a replacement device as needed. Regrettably, we’ve only had the opportunity to comment after the fact, but we’re glad to say that after hearing our concerns, the authors said they would modify the manuscript to provide some explanation of the nature and cause of the errors, before it gets published in final form.
Fitbit’s award-winning products track everyday health and fitness, empowering and inspiring people to lead healthier, more active lives. Understanding there is “no one size fits all” option in fitness, Fitbit has created a diverse product family of affordable trackers that are designed to track all-day trends of everyday activities like steps, distance, calories, stairs climbed, and active minutes. Fitbit’s motivational products and online tools provide users the information that matters most in order to achieve their health and fitness goals.
Fitbit is dedicated to developing easy-to-use, affordable, and the most consistently accurate activity trackers on the market. While there may be a small difference of a few calories or steps between tests, ultimately the success of our products comes from empowering users to accurately see their overall health and fitness trends over time.
For reference, here are articles from Fitbit on accuracy, as well as how Fitbit determines calorie burn: