CNBC: Fitness Bands best for “Relative Purposes”

fitness bands accuracy

A recent class action lawsuit against the popular fitness tech brand, FitBit, raised the question that its heart rate monitors are grossly inaccurate. Last week, a California university – commissioned by the plaintiff’s lawyers – ran tests that agreed the fitness bands are “highly inaccurate”. So CNBC’s watchdog reporter and Senior Editor, Eric Chemi, decided to run a test of his own, wearing 10 fitness trackers all at once, just to see what would happen.

After a quick trip to the local electronics store, and a few borrowed devices from colleagues, Chemi found himself donning 5 fitness bands on each wrist – 10 in all. They included devices made by GarminJawboneMisfitPolarWithings, two FitBit units, (Flex and Charge HR), and a pair of Apple Watches.

Chemi then ran a series of admittedly “unscientific” tests to see how the fitness bands varied in their results for counting steps, calculating distance and – the most controversial of all – heart rate readings.

FitBit Most Accurate in Step Counting

Chemi ran two separate tests while wearing all 10 fitness bands. During the first, he simply went about everyday tasks while wearing the tech devices for a few hours. In the second test, he went for a walk and actually counted aloud to exactly 500 steps.

In the first test, he found the results to vary between devices by more than 20%, with a total range of 1,592 to 2,818 steps. That’s quite a large leap for individuals who are hoping to reach 10,000 steps in a day. The second test’s results weren’t much better, scaling from 446 to 513. He did point out, though, that the FitBit Charge HR had the most accurate results of 505.

Fitness bands accuracy test results

Apple Watch Prevails in Heart Rate Test

Next, he ran a heart rate test, again pointing out that it was done in a very unscientific manner. Chemi hopped on one of the exercise bike’s at the corporate gym, getting a good pace going before putting his finger to his carotid artery to determine he had a BPM of 140.

He did this two days in a row, and both times found wide variance, noting that “the different devices generally undercounted the correct number.” Some read as low as 90, while others were closer to an accurate count at around 130.

However, he said it could have been the placement of the fitness bands on his wrist (each has specific instructions on how/where to wear it), and in some cases, it appeared to be a delayed reaction on the part of the product. Having rested for a few minutes after the workout, “some of the devices displayed a number that was too high,” he said.

With so many possible variables to throw off the test, actual heart rate readings were not posted by CNBC. Chemi did mention that the two Apple Watches had the most accurate results of 134 and 137.

Withings Fitness Bands Go the Distance

Finally, Chemi tested the distance tracking capabilities of the fitness bands. On the first day, while doing typical tasks for 2 hours, the results were incredibly variable. And since he didn’t track how far he actually travelled, impossible to say which is most accurate. On day two, though, he strode upon a treadmill for exactly half a mile, and got similar variance from each device.

“I could see the distances diverge right in front of my eyes,” he wrote. “The more I walked, the more the watches would show numbers growing further apart.”

Before posting the results (image below), he admitted it’s just as likely that the treadmill could have been inaccurately calculating the distance, so again, it’s impossible to say which of the fitness bands was the most inaccurate. If the gym equipment is to be believed, he said “Withings Pulse O2 most closely matched what the treadmill said.”

Fitness bands and distance

Fitness Bands Best for Relative Purposes

In the end, Chemi concluded that fitness bands should not be used as a precise means of any athletic calculations, nor considered medically attuned devices, especially when it comes to heart rate monitoring.

“Maybe the best thing to do is just to use these devices for relative purposes,” he said. So long as the wearer is getting the intended benefit of being more health conscious, and is doing a little more each day to get fit, “that’s the main goal.”

The full video:

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