Jun 21, 2014 05:59 AM EDT By Staff Reporter, UniversityHerald Reporter

Activity monitors are not as accurate as it is believed to be, according to an Iowa State University study. Researchers said that some of the popular devices provide false information 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 in a press release.

For the study, the researchers tested the calorie-counting accuracy of eight fitness bands including the Fitbit One Jawbone Up and Nike FuelBand. Around 30 men and 30 women wore one of the eight monitors for a 69-minute workout that included a series of 13 different activities including typing on a computer keyboard, playing Wii tennis and basketball, and running.

Here is the list based on their error rating:

BodyMedia FIT: 9.3 percent; Fitbit Zip: 10.1 percent; Fitbit One: 10.4 percent; Jawbone Up: 12.2 percent; ActiGraph: 12.6 percent; Directlife: 12.8 percent; Nike FuelBand: 13 percent and Basis Band: 23.5 percent.

Researchers said that the benefits of activity monitors overshadow the imperfections.

"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," Glenn Gaesser, the director of the Healthy Lifestyles Research Center at Arizona State University in Phoenix, said, Huffington Post reports.

Researchers said that the devise was previously treated with scepticism about its ability to monitor sleep and movement.

The finding is published in the journal Medicine & Science in Sports & Exercise.

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