Is your fitness tracker overestimating your workout?

Is your fitness tracker overestimating your workout?

How many steps did you take today? What was your average heart rate? And how well did you sleep? If you know the answer to these questions, chances are you are one of the millions of Americans using a fitness tracker. While this technology is incredibly popular, a new study says they are not incredibly accurate.

Iowa State University researchers found that these devices are between 15 to 40 percent off in determining the amount of calories burned by those wearing them. Over 50 adults wore all seven trackers at the same time and participated in 20 minutes of sedentary activity, 25 minutes of aerobic activity and 25 minutes of resistance training with a five minute break between each activity. The calories burned according to each fitness tracker was compared to the actual calories burned which was measure by breath monitoring system which has been proven to be accurate.

The most accurate trackers were the BodyMedia Core and Fitbit Flex, however they were off by 15 percent. These were followed by Jawbow, Actigraph, Nike, Misfit Shine and the Polar Loop which was 40 percent off of the actual measurement.

Gregory Welk, lead study author, encouraged buyers to be more educated about the accuracy of the various trackers available. “People buy these activity monitors assuming they work, but some of them are not that accurate or have never been tested before,” Welk said in a statement. “These companies just produce a nice-looking device with a fancy display and people buy it.”

This study does not mean that you should stop using your fitness tracker as they can be great motivational tools. In fact, Colleen Eggers, of the Good Samaritan Health and Wellness Center in Downers Grove, Ill., believes that wearing her fitness tracker is helping her to reach her health and fitness goals in 2015.

“I use my Fitbit every day to keep me motivated and on track,” Eggers says. “I make a conscience effort to enter my food every day and keep track of my work outs. It has helped me to be accountable.”

Eggers does caution that when a workout is entered manually into a fitness track the calories burned may be for the average person. However by also wearing a heart rate monitor that tracks calories you can manually enter the calories you burn into the tracker so that you have a more accurate number.

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  1. I know for me, the Fitbit holds me accountable. That was the piece I was missing. I find the Fitbit pretty accurate for sleep. The times it has me going to sleep and waking are pretty accurate. I have restless leg so my husband loves that it is proving proof to his stories of why the blankets end up on the floor.

  2. I have a fitbit force (now discontinued) which I always felt read high. I checked the settings and found that there was a “dominant hand” setting that would suppress the step count for those who moved the hand with the tracker on it a lot. In my own tests, I found it counted about 15% fewer steps. Problem solved.

  3. Excellent article…I am a member of the health and wellness and I am about to embark on my workouts. Thank you.

  4. Michael Heidkamp MS, Exercise Physiologist February 4, 2015 at 12:47 pm · Reply

    Regarding caloric expenditure, there isn’t a single device that is going to be 100% accurate (not even a breath monitoring system which is the most accurate). There are too many variables that go into calculating caloric expenditure. Most people get caught up with the idea of “calories in vs calories out” and end up incorrectly using the data. I suggest that people focus on the strength of these devices.

    The benefits of a fitness device are consistency, and the ability to use them as an awareness tool. I use a fitbit constantly and I can’t remember the last time I looked at the caloric expenditure. I use the steps as my major data point. These devices help you understand your current activity level and allow you to build goals for improvement. Exercise and activity should be counted seperately and each person should work to increase both regularly. I recommend that people use these devices to move more each day with a focus on following a consistent meal plan, independant of their activity. Then follow this with gradually adding structured exercise to their routine. This model will help with managing weight while improving overall health.

  5. I love my FitBit Flex! I don’t use it to track calories burned, but as a motivator to keep moving. I know take the stairs everyday at work and work out every morning. I highly recommend it or motivation alone!

  6. I love my fitbit, too. I don’t really use it for calories but love to see the steps add up each day. It keeps me moving, makes me walk more than usual and work out a little harder. I think it is a great device.

  7. Wear my Fitbit flex all the time. Was amazed at how inactive one can be. It’s a motivating factor. Use it to cunt steps. Valley counter on treadmill vs map my run and fit bit don’t match very well. I started a Fitbit community just search advocate health care and join the community

  8. I’m using a Garmin Vivosmart fitness band. I’ve never presumed the calorie burn number would be accurate, but I find myself moving more so I meet my step goal every day – that has to be a good thing.

  9. I just purchased a Jawbone UP24 and started using it 5 days ago. I like the sleep tracker which seems pretty accurate as does the steps/distance counters. I dont pay much attention to the calories burned since how could that be close to being accurate , unless it is customized for each person. Overall i’m happy with the product and it is keeping me motivated and off the recliner . Just waiting for my club 54 membership to be reinstated for the G-Sam wellness center

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health enews Staff
health enews Staff

health enews staff is a group of experienced writers from our Advocate Aurora Health sites, which also includes freelance or intern writers.