Wrist-worn activity trackers that measure heart rate with a light-emitting diode offer inconsistent heart rate data. While current trackers may help to motivate people to engage in healthy behaviors, more research is needed before clinicians can use the data to advise patients about health issues or conduct clinical trials that require a high level of accuracy and reliability for heart rate measurement. The clinical observation is published in Annals of Internal Medicine.

Researchers at the University of Wisconsin in Madison, WI, studied 4 commercial, wrist-worn activity trackers to determine the accuracy of their heart rate monitoring. Study participants were 40 healthy consenting adults aged 30 to 65 without cardiovascular conditions. Each participant wore 2 trackers on each wrist in random order. Seated participants were then connected to an electrocardiograph to measure resting heart rate at one minute intervals for 10 minutes using the electrocardiograph and each of the 4 trackers. The measures were repeated while participants walked on the treadmill. Of the four commercial trackers tested, all performed better at rest than during moderately active exercise when compared with measures taken by electrocardiograph, and some of the activity trackers were more consistent than others.