An Iowa State University study has found that popular fitness trackers are, on average, off by about 15 to 30 percent.
That means your tracker may not be accurately calculating the energy you’re expending during physical activity.
The study consisted of more than 50 people ranging in age from 18 to 65 years old using both consumer- and medical-grade fitness trackers.
The participants first did a sedentary task for 20 minutes, such as reading, working at a computer or watching a video.
That was followed by 25 minutes of aerobic activity of their choice, and then 25 minutes of resistance training. Each activity was separated by a 5-minute rest period.
Among the trackers tested, the medical-grade devices had the lowest rates of error.
Accuracy in measuring resistance activity was a challenge for all of the monitors tested – with error rates for that type of activity ranging from 20 to more than 52 percent.
Issues with accuracy notwithstanding, fitness trackers can still be beneficial to your efforts to stay in shape, researchers say.
“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,” Greg Welk, professor of kinesiology at Iowa State University, said.
