Researchers tested 10 of the top-selling smartphone apps and devices in the US by having 14 participants walk on a treadmill for 500 and 1,500 steps, each twice (for a total of 56 trials), and then recording their step counts.
The study was led by researchers at the Perelman School of Medicine and the Center for Health Incentives and Behavioural Economics at the University of Pennsylvania.
"In this study, we wanted to address one of the challenges with using wearable devices: they must be accurate," said lead study author Meredith A Case, a medical student at Penn.
"After all, if a device is going to be effective at monitoring - and potentially changing - behaviour, individuals have to be able to trust the data. We found that smartphone apps are just as accurate as wearable devices for tracking physical activity," she said.
Each of the study participants, all healthy adults recruited at Penn, had wearable devices on during the treadmill trials. Each participant wore one pedometer and two accelerometers on the waistband; three wearable devices on the wrist; two smartphones in pants pockets, with one running three apps and the other running one.
At the end of each trial, step counts from each device were recorded. The data from the smartphones were only slightly different than the observed step counts, but the data from the wearable devices differed more.
"Since step counts are such an important part of how these devices and apps measure physical activity, including calculating distance or calories burned, their accuracy is key," said senior author Mitesh S Patel, assistant professor
of Medicine and Health Care Management at Penn.
"Compared to the 1 to 2 percent of adults in the US that own a wearable device, more than 65 percent of adults carry a smartphone.
"Our findings suggest that smartphone apps could prove to be a more widely accessible and affordable way of tracking health behaviours," Patel said.
The research was published in the journal JAMA.
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