WASHINGTON — More and more people are wearing activity trackers in order to count the number of steps they take each day, and the number of calories they work off. But a study finds that they have some serious accuracy problems when it comes to certain types of physical activity.
Researchers at Ball State University tested the Fitbit Flex, One and Zip, and the Jawbone UP24, on 30 people to gauge how accurately they measured the steps subjects took and the calories they burned while walking, jogging, cycling and performing household tasks such as sweeping and laundry. They also checked the devices while subjects engaged in passive activities such as lying down and using a computer, Indiana Public Media reports.
The researchers found that the devices worked well at measuring steps during “structured activity” such as walking or jogging, as well as correctly showing no steps taken by someone lying down — “similar to much less expensive pedometers,” Ball State exercise physiology professor Alex Montoye said in a statement.
But they overestimate the number of calories burned by walking or jogging, and underestimate the caloric impact of household activities, the study finds. And they all underestimated the amount of exertion subjects expended while cycling.
The study concludes that if you’re looking to one of these devices to monitor your activity, it’s better suited to “structured ambulatory activity” then to estimating your overall exertion.
