Fitbit PurePulse accuracy under fire

fitbit-heartrateA study by Edward Jo, Ph.D. and Brett A. Dolezal, Ph.D., looked at the accuracy of Fitbit’s PurePulse. Given Fitbit has been sued under a class action regarding the accuracy of PurePukse, this study from the California State Polytechnic University in Pomona will not help Fitbit’s cause.

The researchers tested Fitbit PurePulse wearables on 43 healthy individuals and found the Fitbit was sometimes out by more than 20 beats per minute.

The full study, titled Validation of the Fitbit SurgeTM and Charge HRTM Fitness Trackers [PDF link], found:

  • During moderate to high-intensity exercise, the Charge HR recorded a heart rate that differed from the ECG by an average of 15.5 bpm
  • During moderate to high-intensity exercise, the Surge recorded a heart rate that differed from the ECG by an average of 22.8 bpm
  • In addition to being inaccurate, the PurePulse Trackers are also inconsistent

Their conclusion:

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.

We are entering an era when individuals are able to purchase all sorts of equipment that was previously only available to health professionals. I’ve got a pulse oximeter, blood pressure monitor, electronic thermometer and a body composition measurement device. My expectation is that the devices are reasonably accurate but not medical grade.

However, the level of variation revealed in this study is troubling. If you’re exercising at a high intensity and using your heart rate to monitor your effort, the differences found in this study could be the difference between working at high intensity and working at a dangerous intensity.

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