How Accurate Is Your Activity Monitor? Fitbit, Jawbone And Others Put To The Test

06/20/2014 04:58pm ET
Four fitness trackers are shown in this photograph, in New York, Monday, Dec. 16, 2013. They are, from left, Fitbit Force, Jawbone Up, Fitbug Orb, and the Nike FuelBand SE. For aspiring health nuts and to inspire couch potatoes to get active, the latest crop of fitness gadgets will record much more than how many steps you took on any given day. From sleep patterns to calorie intake, mood and progress toward exercise goals, few aspects of life are left un-tracked for those in search for a more quantified self. (AP Photo/Richard Drew)

Your trusty activity monitor says you burned 300 calories during your morning run, but can you really trust it?

According to a study conducted by researchers at Iowa State University, activity monitors may not be as accurate as you'd expect them to be, with some of the most popular devices on the market getting it wrong at least 10 percent of the time.

“People buy these activity monitors assuming they work, but some of them are not that accurate or have never been tested before. These companies just produce a nice-looking device with a fancy display and people buy it,” study author Gregory Welk said, per a media release.

For the study, which was published in the journal Medicine & Science in Sports & Exercise, Welk and his team tested the calorie-counting accuracy of eight activity monitors, including the Fitbit One, Jawbone Up and Nike FuelBand.

Here's how they fared (ranked by error rating):

  1. BodyMedia FIT: 9.3 percent
  2. Fitbit Zip: 10.1 percent
  3. Fitbit One: 10.4 percent
  4. Jawbone Up: 12.2 percent
  5. ActiGraph: 12.6 percent
  6. Directlife: 12.8 percent
  7. Nike FuelBand: 13 percent
  8. Basis Band: 23.5 percent

The accuracy of activity monitors has come under scrutiny before.

Researchers, for instance, previously expressed skepticism about the devices' ability to track sleep and movement.

Still, despite the imperfections, some researchers insist the benefits of activity monitors outweigh the flaws.

“They may not be accurate [for counting calories]," Glenn Gaesser, the director of the Healthy Lifestyles Research Center at Arizona State University in Phoenix, told The New York Times last year. “But for many people, they’re inspirational, and if using one gets someone to move more, then as far as I’m concerned, it’s serving a good purpose.”

(Hat tip, CNN)

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