If you think your Fitbit is better at counting daily steps than your smartphone, you may want to think again. A new study suggests that many smartphone apps are just as good as specialized wearable devices at tracking physical activity.
In the study, 14 participants donned a number of wearable devices and also carried several smartphones loaded with activity apps, while they walked on a treadmill for a set number of steps (either 500 or 1,500). The researchers then compared participants' actual step count with the number recorded by each of the devices or apps.
The participants wore three devices on their waist (the Fitbit One, the Fitbit Zip and the Yamax Digi-Walker SW-200 pedometer) and three devices on their wrist (the Yamax Digi-Walker SW-200, the Jawbone Up24 and the Nike Fuelband). Participants also had one smartphone in each of their pants pockets: An Apple iPhone 5s that was running three physical activity apps (Fitbit, Health Mate by Withings and Moves by ProtoGeo Oy), and a Samsung Galaxy S4 that was running one physical activity app (Moves by ProtoGeo Oy).
Each participant completed the treadmill walk four times, for a total of 56 walking trials. Overall, both the wearable devices and smartphone apps were pretty accurate at tracking steps counts, the researchers said. [ Best Fitness Apps for 2015 ]
The waist-worn wearable devices came closest to reflecting participants' actual step counts: These devices reported step counts that were between 0.3 percent lower and 1 percent higher than the participants' actual step count.
The smartphone applications used in the study reported step counts that were between 6.7 percent lower and 6 percent higher than actual step counts. Although there will be some variability in such step counts, depending on where on his or her body a person keeps the smartphone, it's likely that those apps will still be pretty accurate if the smartphone is carried in other locations, such as in a purse or on the hip, said study researcher Dr. Mitesh S. Patel, an assistant professor of medicine and health care management at the University of Pennsylvania School of Medicine
Wearable devices worn on the wrist were more variable in their step counts, reporting counts that were between 22.7 percent lower to 1.5 percent higher than the participants' actual step counts.
Gadgets that track people's physical activity have the potential to help people become more active, but only about 1 to 2 percent of U.S. adults own a wearable, whereas more than 65 percent carry a smartphone, the researchers said.
"Our findings suggest that smartphone apps could prove to be a more widely accessible and affordable way of tracking health behaviors," Patel said in a statement.
The findings may also reinforce people's trust in using smartphones and wearables to accurately track physical activity. Patel noted that these gadgets often use step counts to calculate other measures of physical activity, such as distance walked and calories burned, so "their accuracy is key."
In an interview with Live Science last year, Dr. Clay Marsh, who at the time was chief innovation officer at Ohio State University Wexner Medical Center, said that a device's accuracy at counting steps is less important than its consistency. As long as a device is consistent in the way it measures movement, it can be useful because it will show your progress, Marsh said.
Because the new study was conducted in a controlled lab setting with a limited number of devices and applications, the results should be confirmed in different settings with other devices and apps, the researchers said.
The study is published today (Feb. 10) in the Journal of the American Medical Association.
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