Which Fitness Monitor is Most Accurate?

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AMES, Iowa -- We've all heard we need to get up and move more throughout the day. That has more people wearing fitness monitors to track their exercise. A new study by Iowa State University researchers looks at how accurate those devices are.

Iowa State University Professor of Kinesiology Greg Welk says, "The market is exploding and new monitors are coming on the market every day."

Fitness monitors measure movement letting you know how many calories you're burning and how much you're moving throughout the day. Many people use it for weight loss goals. Researchers have long used monitors to track movement, but the technology became available for health-conscience consumers a few years ago. Now, several companies sell devices for $100 to $150.

ISU Graduate Student Yang Bai is on the team of researchers. She says, "I have lots of friends and family. They start to use those trackers, and then they keep asking me questions, how accurate are those and which one is better than the other ones?"

ISU researchers recruited 60 study participants to find out. Each spent five minutes doing 12 different real world activities like walking, running and sitting. Researchers compared the monitors you would buy at the store to the established ones scientists use for studies.

Welk says, “They're not 100 percent accurate, so I think people have to know these are estimates, but they're within 10 to 15 percent error of what a measured value of energy expenditure would be, which isn't bad."

The research was published in the journal Medicine and Science in Sports and Exercise. The top performer in the study was Bodymedia Fit. It had a 9.3% error rating. The Fitbit Zip and Fitbit One followed with about a 10% error rating. Jawbone Up, Actigraph and Directlife all had about a 12% error rating. Nike Fuel Band followed with 13% and Basis Band was about 23% off, according to the study.

ISU researchers plan to start a new study soon. They’ll test new models coming on the market. They’ll also look into the accuracy of the monitors in different kinds of settings. Welk says, "We'll be testing some of those monitors under a simulated workout condition where participants wear the monitors for 25 minutes doing an aerobic routine, then 25 minutes doing a resistance routine, similar to what they could do in a fitness center."

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