Saturday, February 14, 2015

Just How Accurate Are Those Activity Trackers?

I've seen many of my patients wearing an activity tracker and I'm sure you've seen someone sporting one on their wrists too. 

Just last week at my hydrotherapy/ deep water running session one of my patients was wearing one in the pool and she complained afterwards that she was really tired from the session but her tracker didn't seem to agree and did not track what she did! Another patient commented besides having a rather "cool" object on his wrist, he used his tracker to monitor his sleep.

Here's my patient with his"cool" Jawbone activity tracker
Well just how accurate and useful are these activity trackers?

ACE (American Council on Exercise) commissioned a study on activity trackers to measure their accuracy with regards to step count and calorie expenditure.

The following brands were tested - Nike+ Fuelband, Fitbit, Jawbone UP, Adidas MiCoach and BodyMedia Fitcore which has since been bought by Jawbone).

The subjects (aged 18 to 44) wore the trackers while walking, running on a treadmill, exercising on an elliptical machine, and performed other exercises including agility ladder drills, shooting free throws and T drills (for baseball). In order to compare, the participants also wore portable metabolic analysers and the NL-2000 pedometer, which were considered accurate and reliable by researchers.

And what did they find? Besides providing wearers with a reasonable estimate of how active they are in the daily lives , activity trackers may not be as accurate as some users believe. 

Some underestimated numbers while others overestimated them. This is true when tracking more complex activities such as playing basketball, weight lifting and cross training. Each brand of tracker has its own strengths and weaknesses. 

The "best" tracker for any given individual depends on his/ her biomechanics and what he/she wants to measure. For instance the researchers found that the Jawbone UP was the most accurate for step count while not so accurate while measuring calorie expenditure running on a treadmill.

Despite not being too accurate with tracking expenditure, the researchers found that people wearing them became 30 to 40 percent more active so maybe accuracy does not matter as much since the trackers got users to keep moving. They can also help to show  wearers when they could move more during their daily lives.

And even if your activity tracker isn’t 100 percent accurate, the researchers say you can still benefit from the feedback it provides. 
Before you go and buy yours, bear in mind that some trackers studied may not be available any more and companies do update their technology so science may not be able to keep up with technology.
Stackpool C, Porcari JP et al (2013). Accuracy Of Various Activity Trackers In Estimating Steps Taken And Energy Expenditure. Masters thesis. University of Wisconsin- La Crosse. See the ACE article here.

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