Studies show Fitbit trackers are ‘highly inaccurate’

“A class action lawsuit against Fitbit may have grown teeth following the release of a new study that claims the company’s popular heart rate trackers are ‘highly inaccurate,'” Kalyeena Makortoff reports for CNBC.

“Researchers at the California State Polytechnic University, Pomona tested the heart rates of 43 healthy adults with Fitbit’s PurePulse heart rate monitors, using the company’s Surge watches and Charge HR bands on each wrist. Subjects were then hooked up to a BioHarness device that produced an electrocardiogram (ECG), to record the heart’s rhythm against the data being produced by Fitbit’s devices,” Makortoff reports. “Comparative results from rest and exercise — including jump rope, treadmills, outdoor jogging and stair climbing — showed that the Fitbit devices miscalculated heart rates by up to 20 beats per minute on average during more intensive workouts. ‘The PurePulse Trackers do not accurately measure a user’s heart rate, particularly during moderate to high intensity exercise, and cannot be used to provide a meaningful estimate of a user’s heart rate,’ the study stated.”

“A separate study by Ball State University in Indiana and journalists at NBC-affiliated TV station WTHR released in February also showed that the Fitbit Charge HR missed heartbeats, marking an average heart rate error of 14 percent,” Makortoff reports. “‘Calculating a heart rate that’s off by 20 or 30 beats per minute can be dangerous — especially for people at high risk of heart disease,’ the report said.”

Read more in the full article here.

MacDailyNews Take: Fitbit peddles inaccurate junk to the undiscerning.

Apple Watch heart rate data vs. Mio dedicated heart rate monitor – May 7, 2015
Apple explains Heart Rate on Apple Watch technology – April 20, 2015


  1. I’d like to believe Apple Watch is much more accurate, but based on personal experience, it isn’t. When it actually gets a reading it seems to be great, but far too often the reading will be way off. I’ll be running up seven flights of stairs, heart racing, and it’ll show 60-70bpm. After exiting the workout app and going to the HR glance, and after several readings, it’ll finally show something more accurate like 120 bpm, which is 30-40bpm off of what my HR actually was at its peak.

    To be fair, I think this is a problem inherent in wrist-worn HR monitors. Blood flow is uneven to the extremities, especially when doing exercises that aren’t rhythmic like running, but weightlifting or Yoga. Selecting the “Other” workout vs a “Outdoor Walk” for example, also makes a big difference. The former, under the same conditions/time, will show a 50%+ higher calorie burn.

      1. Nick is right. I run with both a Garmin Forerunner with a heart rate monitor around my chest, as well as my Apple Watch. My usual heartbeat at my normal speed/cadence is ~147 BPM. My Garmin watch is spot on whereas my Apple Watch often is ~170 BPM. However, after about 15 minutes, the Apple Watch settles down and closely tracks the Garmin, but the initial readings are way off.

        1. If you plot the difference on the recorded data, is it more accurate then or does it show the 15 min lag even after capture?

      1. It seems like some people are easier to read than others, for whatever reason. For me I have to make sure it’s not too tight nor too loose. For others, using my same watch to test it, it doesn’t seem to matter so much.

        1. I think you’re right, it’d be nice to know some of the variables involved though. I wear my Watch at the ideal tightness as far as I can tell. It’s frustrating when you know it’s spot on sometimes (measuring your HR by hand or with a second monitor simultaneously), while other times it’s way off. If physiology is the issue, it’s hard to imagine what Apple can do hardware-wise in future models. Hopefully the sensors get better.

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