Newswise — The testing of 10 smartphone applications and wearable devices intended to track physical activity found that most were accurate in tracking step counts, according to a study in the February 10 issue of JAMA.

Despite the potential of pedometers to increase physical activity and improve health, there is little evidence of broad adoption by the general population. In contrast, nearly two-thirds of adults in the United States own a smartphone and technology advancements have enabled these devices to track health behaviors such as physical activity and provide convenient feedback. New wearable devices that may have more consumer appeal have also been developed. Even though these devices and applications might better engage individuals in their health, there has been little evaluation of their use, according to background information in the article.

Mitesh S. Patel, M.D., M.B.A., M.S., of the University of Pennsylvania, Philadelphia, and colleagues recruited healthy adults at a university to evaluate the accuracy of smartphone applications and wearable devices compared with direct observation of step counts. Participants walked on a treadmill set at 3.0 mph for 500 and 1,500 steps, each twice. An observer counted steps using a tally counter. At the end of each trial, step counts from each device were recorded.

The participants used applications and devices that were selected from among the top sellers in the U.S.: the Digi-Walker SW-200 pedometer (Yamax); the Zip and One (Fitbit) accelerometers; the wearable devices Flex (Fitbit), the UP24 (Jawbone), and the Fuelband (Nike); an iPhone 5s (Apple) simultaneously running 3 iOS applications, Fitbit (Fitbit), Health Mate (Withings), and Moves (ProtoGeo Oy); and a Galaxy S4 (Samsung Electronics) running 1 Android application, Moves (ProtoGeo Oy).

Across all devices, 552 step count observations were recorded from 14 participants in 56 walking trials. Participants were 71 percent female, with an average age of 28 years. The researchers found that compared with direct observation, the relative difference in average step count ranged from -0.3 percent to 1.0 percent for the pedometer and accelerometers, -22.7 percent to -1.5 percent for the wearable devices, and -6.7 percent to 6.2 percent for smartphone applications. Findings were mostly consistent between the 500 and 1,500 step trials.

“Data from smartphones were only slightly different than observed step counts, but could be higher or lower. Wearable devices differed more and 1 device reported step counts more than 20 percent lower than observed. Step counts are often used to derive other measures of physical activity, such as distance or calories burned. Underlying differences in device accuracy may be compounded in these measures,” the authors write.

“Increased physical activity facilitated by these devices could lead to clinical benefits not realized by low adoption of pedometers. Our findings may help reinforce individuals' trust in using smartphone applications and wearable devices to track health behaviors, which could have important implications for strategies to improve population health.”(doi:10.1001/jama.2014.17841; Available pre-embargo to the media at

Editor’s Note: This study was funded in part through a grant from the National Institute on Aging. Dr. Patel was supported by the U.S. Department of Veteran Affairs and the Robert Wood Johnson Foundation. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, etc.

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