SAN FRANCISCO • Many users of activity trackers have always harboured a suspicion: How accurate are these things?
A handful of tests by journalists and researchers have tried to bring clarity to the issue. Results, alas, have been mixed.
The latest study, released by the plaintiffs in a class-action lawsuit against Fitbit, found that the pulse-monitoring technology used in its wrist-bound Surge and Charge devices was "highly inaccurate during elevated physical activity".
Researchers from California State Polytechnic University, Pomona, had 43 subjects wear the devices as they ran, jogged and jumped rope, among other activities, and then compared the readings with those of an electrocardiogram.
During moderate to high-intensity exercise, Fitbit's sensor was off by an average of about 19 beats a minute.
The study, which was not peer-reviewed and was commissioned by the plaintiffs' law firm, drew a strong denunciation from Fitbit, which released a statement calling it "biased, baseless and nothing more than an attempt to extract a payout from Fitbit".
The lawsuit accuses the company of misleading customers about the reliability of the PurePulse technology in its heart-monitoring wristbands, and says this could potentially have dire medical consequences.
Fitbit, based in San Francisco, is a leader in the wearables industry with a market capitalisation of about US$3 billion (S$4.1 billion). Last year, it sold 21.3 million devices, almost double its sales a year earlier.
Dr Alex Montoye, an assistant professor of clinical exercise physiology at Ball State University, who is not connected to the lawsuit, said the Pomona study needed rigorous vetting before any conclusions could be drawn. "There's a clear interest in finding something in one direction," he said. "That doesn't mean that the science is bad."
In another study on Jawbone and Fitbit devices, a team led by Dr Montoye found that both devices overcounted and undercounted as the activities intensified.
NEW YORK TIMES