Are activity trackers accurate? Researchers put them to the test

Research Triangle Park, NC – It’s a case of good news, bad news for people who wear activity trackers on their wrists.

First, the good news: Such devices reliably and accurately measure step counts during the day, according to a study from the University of North Carolina Gillings School of Global Public Health and RTI International. The bad news: The devices score lower in terms of measuring expended calories and sleep time. Findings on distance and active minutes were inconclusive.

Researchers announced their findings after a systematic review of 22 published articles analyzing popular devices from manufacturers such as Fitbit and Jawbone.

The trackers’ step-counting function proved to be “accurate both in the lab and in the field” in multiple analyses, researchers said in a press release. However, some studies indicated that the devices underestimated calories used and overestimated sleep time.

Experts provided the following recommendations to improve the accuracy of the trackers:

• Wear the device in the same position every day.
• Submit correct height and weight at initial setup; provide updates for significant changes.
• Calibrate the correct length of a walking stride (if the device allows for this function).

“Wearable devices that track physical activity, sleep and other behaviors are growing significantly in popularity,” study co-author Robert Furberg said in the release. “We conducted this review to understand how accurate these devices are.”

The review was published online Dec. 18 in the International Journal of Behavioral Nutrition and Physical Activity.