Public Release: 

Smartphone apps just as accurate as wearable devices for tracking physical activity

JAMA paper among the first to compare smartphone app vs. Wearable device accuracy

University of Pennsylvania School of Medicine

PHILADELPHIA - 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 10 of the top-selling smartphone apps and devices in the United States 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. Led by researchers at the Perelman School of Medicine and the Center for Health Incentives and Behavioral Economics at the University 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 behavior 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. After all, if a device is going to be effective at monitoring -- and potentially changing -- behavior, individuals have to be able to trust the data," said lead study author Meredith A. Case, BA, a medical student at Penn. "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

  • Pants 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 percent relative difference in mean step count), but the data from the wearable devices differed more (with a range of -22.7 to -1.5 percent).

"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, MD, MBA, MS, assistant professor of Medicine and Health Care Management at Penn and an attending physician at the Philadelphia VA Medical Center. "Compared to the one to two percent of adults in the U.S. 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 behaviors."

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The other Penn study author is Kevin G. Volpp, MD, PhD. This study was funded in part through a grant from the National Institute on Aging (RC4 AG039114-01). Patel's work was supported by the Department of Veterans Affairs and the Robert Wood Johnson Foundation.

Penn Medicine is one of the world's leading academic medical centers, dedicated to the related missions of medical education, biomedical research, and excellence in patient care. Penn Medicine consists of the Raymond and Ruth Perelman School of Medicine at the University of Pennsylvania (founded in 1765 as the nation's first medical school) and the University of Pennsylvania Health System, which together form a $4.3 billion enterprise.

The Perelman School of Medicine has been ranked among the top five medical schools in the United States for the past 17 years, according to U.S. News & World Report's survey of research-oriented medical schools. The School is consistently among the nation's top recipients of funding from the National Institutes of Health, with $392 million awarded in the 2013 fiscal year.

The University of Pennsylvania Health System's patient care facilities include: The Hospital of the University of Pennsylvania -- recognized as one of the nation's top "Honor Roll" hospitals by U.S. News & World Report; Penn Presbyterian Medical Center; Chester County Hospital; Penn Wissahickon Hospice; and Pennsylvania Hospital -- the nation's first hospital, founded in 1751. Additional affiliated inpatient care facilities and services throughout the Philadelphia region include Chestnut Hill Hospital and Good Shepherd Penn Partners, a partnership between Good Shepherd Rehabilitation Network and Penn Medicine.

Penn Medicine is committed to improving lives and health through a variety of community-based programs and activities. In fiscal year 2013, Penn Medicine provided $814 million to benefit our community.

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