GOLDEN VALLEY, Minn. - When wearing her fitness tracker, Cynthia Hotvedt of Robbinsdale, does not walk alone.
"We went to a family reunion last summer," she said. "It turns out one of my cousins had a Fitbit. We got to talking about it and we all decided to buy them at the family reunion."
She said their group cleaned out two local stores. Now she walks alongside those relatives every single day, thanks to the fitness tracker technology. On her laptop, she can see how many miles each has walked every week.
"We're super competitive so you can go on the website and see what everybody else is doing and you can say, 'Ooh, if I just had 100 more steps I could beat my cousin Christine,'" Hotvedt said.
Fitness trackers, worn on the wrist or hip, can calculate things like steps taken each day and calories burned. They are a popular purchase for those who want to get motivated to move.
Now, a new study out of Iowa State University has looked at the accuracy of these devices. That study, to be published this summer in the journal Medicine and Science in Sports and Exercise, looked at how accurate seven fitness trackers were when it comes to calories burned.
The following trackers were tested: BodyMedia FIT, Fitbit Zip, DirectLife, Fitbit One, Jawbone UP band, Nike+ Fuel Band and the Basis B1 Band.
When it comes to calories burned, the study found all of them were all pretty accurate. Overall, readings were within 10 percent of actual energy expenditure.
The study found the Body Media Fit was most accurate with the Fitbit Zip second.
"They've come a long way. The ones that they had 10-15 years ago were not so good," said Dr. Steve Greer, a sports medicine physician with Health Partners Orthopaedics and Sports Medicine.
Greer said while fitness trackers may not be accurate enough for an elite athlete, "For your average person to get a little bit more activity than they're used to getting, I think 10 percent is more than adequate."
Hotvedt said her fitness tracker is a great motivator. Of course, her competitive relatives help, too.
"I would say since getting this Fitbit last summer, I have moved more every single day in the last 10 months," she said.
Study author Jung-Min Lee, now at University of Nebraska at Omaha, said the fitness trackers were tested in the summer of 2013. Lee said most of those models remain on the market but there are new versions of the Jawbone UP and Nike+ Fuel Band.