Are You Being Fooled By Your Fitness Tracker?

It can count your steps and log your sleep, but your activity tracker may not be as accurate as you think during certain exercise routines


It's no secret that we're a little bit obsessed with our fitness trackers at Shape, but determining which one is the best bet isn't easy (and we do this for a living!). But new research may help shed some light on which tracker is the best option for you, while serving as another reminder that our handy gadgets aren't exactly the be-all-end-all-at least when it comes to tracking certain stats.

According to a study recently published in the journal Medicine & Science in Sports & Exercise, activity trackers can provide a good overall estimate of calories burned, but they're less accurate when measuring certain activities, such as strength training. (Want to think outside the box? See 5 Cool New Ways to Use Your Fitness Tracker That You Probably Haven't Thought Of.)

Researchers at Iowa State University (the same ones, in fact, who last year discovered that your fitness tracker may be overestimating your calorie burn) tested four consumer fitness trackers-the Fitbit Flex, Nike+ FuelBand SE, Jawbone UP 24, and Misfit Shine-to see how well they measured aerobic, sedentary, and resistance activity. (They also tested two research monitors-the BodyMedia Core and Actigraph GT3X-shown in the results chart below, but since these aren't fitness trackers you or we would use at the gym, we've omitted them from our analysis.)

In the study, 56 participants were asked to complete 20 minutes of sedentary activity-such as reading a book, working at the computer, or watching a video-followed by 25 minutes of their aerobic activity of choice, and then 25 minutes of a resistance exercise with 5 minutes rest between each activity (this schedule was designed to mimic real life daily activities).

Overall, the Fitbit Flex was the most accurate, with the lowest error rate of 16.8 percent. However, it's worth noting that Nike and Jawbone were a very close second and third, at 17.1 and 18.2 respectively. The least accurate-with a 30.4 percent error rate-was the Misfit Shine.

However, when looking at the activity breakdowns, certain trackers definitely performed better than others. For both cardio and strength training, the Nike+ Fuelband SE beat out the others by a significant lower percentage of error.


And while accuracy is obviously important-after all, the worst error rate of 60 percent on a three mile run means it's over or under estimating your calorie burn by almost 180 calories-it's not everything. "I think the key to a consumer is not so much if the activity monitor is accurate in terms of calories, but whether it's motivational for them and keeps them accountable for activity in a day," said Greg Welk, Ph.D., professor of kinesiology at Iowa State University.

So while it's helpful to keep in mind that your tracker likely isn't giving you a totally accurate measurement of your gym time, if yours gets you to the gym, no need to ditch it! To ensure your tracker is more than just a sporty accessory, read up on the The Right Way to Use Your Fitness Tracker and Your Fitness Tracker's Stats-Explained to translate all that tracking into healthier behavior.

Was this page helpful?
Related Articles