Smartphones as good as wearables for tracking physical activity, says report
February 18, 2015
Although wearable devices have received significant attention for their ability to track an individual’s physical activity, most smartphone applications are just as accurate, according to a new research letter in Jama.
The study tested ten of the top-selling smartphone apps and devices in the USA by having 14 participants walk on a treadmill for 500 and 1500 steps, each twice (for a total of 56 trials), and then recording their step counts. Led by researchers at the Perelman School of Medicine and Center for Health Incentives & Behavioral Economics at theUniversity of Pennsylvania, this study is a follow-up to a recent Jama viewpoint suggesting that there’s little evidence that wearable devices alone can change behaviour and improve health for those that need it most.
“In this study, we wanted to address one of the challenges with using wearable devices: they must be accurate,” said lead study author Meredith 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.”
Each of the study participants, all healthy adults recruited at Penn, had the following devices on during the treadmill trials: waistband – one pedometer and two accelerometers; wrists – three wearable devices; and trouser pockets – two smartphones, 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 (with a range of -6.7 to 6.2 per cent relative difference in mean step count), but the data from the wearable devices differed more with a range of -22.7 to -1.5 per cent.
“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 Patel, assistant professor of medicine and healthcare management at Penn and an attending physician at the Philadelphia VA Medical Center. “Compared to the one to two per cent of adults in the USA that own a wearable device, more than 65 per cent 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.”
The other Penn study author was Kevin Volpp. This study was funded in part through a grant from the National Institute on Aging. Patel’s work was supported by the Department of Veterans Affairs and the Robert Wood Johnson Foundation.