Are Fitness Trackers Accurate?
Written by Editor   
Monday, May 29, 2017 09:05 PM

Next-generation activity trackers are wrist-worn trackers measuring heart rate with light-emitting diode (LED) reflection from the skin, reflecting tiny changes in skin blood volume. It is easy to understand their convenience, but their accuracy is questionable.  The data supporting that use has been lacking.

This study tested four trackers on the market (Fitbit Surge, Basis Peak, Fitbit Charge, and Mio Fuse) against the gold standard ECG at rest and at 65 percent of maximum heart rate during exercise on the treadmill. Participants were healthy adults ages 30 to 65 years without cardiovascular conditions. Two trackers were randomly placed on right versus left wrist or proximal versus distal location on the wrist. Heart rates were measured at one-minute intervals for 10 minutes at rest and during exercise.

Fitbit Surge (Fitbit) had the highest agreement with the ECG results (range 5.1 to 4.5 beats/min), followed by the Mio Fuse (Mio Global; 7.8 to 9.9 beats/min), Fitbit Charge (Fitbit; range 10.5 to 9.2 beats/min), and Basis Peak (Basis; range 17.1 to 22.6 beats/min).

Although the level of agreement with ECG results and the repeatability coefficient was comparable to ECG at rest for some devices such as the Fitbit Surge, the accuracy and precision of the measurements seems to vary a lot during exercise.

While these wrist devices may provide a sufficient approximation for assessing daily activity and exercise, more work is needed before using the data clinically.