Fitbit will happily advertise the accuracy of its PurePulse heart rate technology in both the Charge HR and Surge, but are the readings accurate?

Participants were assigned to perform several indoor and outdoor tasks, including self-paced jogging, jump roping, treadmill running, stair climbing, and plyometrics, all of which were either followed or preceded by rests and all of which were performed for five minutes.

Unfortunately for Fitbit, results showed that the Charge HR recorded a heart rate that differed from the ECG s data by 15.5 beats per minute bpm .

However, the difference increased to 12.5 bpm when a participant s heart rate reached 124 bpm, a heart rate associated with low intensity activities.

As such, one can t help but think this nugget of information slightly skews the results.

Even so, a 2014 article in the Berkeley Science Review and a February 2016 informal investigation by Indiana news station WTHR also arrived to similar inconsistent results with Fitbit s trackers, with inconsistencies only increasing as the exercise grew in intensity.

The text above is a summary, you can read full article here.