Fitbit , Jawbone And Others: How Accurately Do Fitness Trackers Measure Calories Burned?

If you want to have a decent estimate of calories you just burned, you can go to any fitness website and look at a table for that kind of activity - or you can spend $70 on a Misfit Shine and get an error rate of over 30 percent.

However, if spending $70 to be motivated to exercise will do the trick, perhaps accuracy is not a problem.

Yet the American Council on Science and Health wants to be sure you are getting the health benefit you pay for - and so do a team from Iowa State University. For their analysis, they tested the Fitbit Flex, Nike+ FuelBand SE, Jawbone UP 24, and Misfit Shine to determine their accuracy in measuring sedentary, aerobic, and resistance activity. Two research monitors, the BodyMedia Core and Actigraph GT3X+, were also included in the study.

They found that the BodyMedia Core had a rate of error of 15.3 percent while the Misfit Shine was the least accurate, with a 30.4 percent error rate. When it comes to things like strength training, the accuracy for all of them was suspect.

The full results are published in Medicine&Science in Sports & Exercise. The following is a breakdown of error rates for each monitor based on activity:

For the test, 56 participants completed 20 minutes of sedentary activity - examples of sedentary activity are things like reading a book, getting smarter at the ACSH.org website, or watching a video. Then they performed 25 minutes of aerobic activity and 25 minutes of resistance exercise with 5 minutes of rest in between.

Some monitors overestimated or underestimated all three activities while some overestimated one type and underestimate the other two categories.

The results shouldn't be an excuse to procrastinate when it comes to exercising, all motivation is good motivation. So if wearing a device gets you moving, they are still worth the money.