If you’re looking to track your daily activity, you may not need to buy an expensive fitness tracker, as a new study from the University of Pennsylvania shows that your iPhone is just as accurate at tracking activity as a dedicated wearable device.
“In this study, we wanted to address one of the challenges with using wearable devices: they must be accurate,” said Penn medical student and lead study author Meredith A. Case, BA. “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. We found that smartphone apps are just as accurate as wearable devices for tracking physical activity.”
To gather data for the study, researchers equipped 14 subjects with up to 6 wearable devices: a Digi-Walker SW-200 pedometer, the Fitbit Zip and One clip-on trackers and a Flex wristband, Jawbone’s Up24, and the Nike Fuelband. In addition, an iPhone 5s running the Fitbit app, Withings’s Health Mate app, and ProtoGeo Oy’s Moves app was placed in one pocket, while in the other pocket sat a Samsung Galaxy S4 running Moves on Android.
Each participant then walked on a treadmill at 3 miles per hour, twice each for 500 steps and 1,500 steps. The smartphone apps showed a relative difference of -6.7 percent to 6.2 percent difference form the steps the researchers observed the participants taking, while the wearables ranged -22.7 percent to -1.5 percent.
The numbers show the Nike’s Fuelband measurements as off the most, with Jawbone’s Up24 and Fitbit’s Flex showing the second and third-largest deviations. The Fitbit Zip and One were close to perfect.
Apple’s iPhone 5s and iPhone 6 and iPhone 6 Plus all include a motion coprocessor which constantly tracks a user’s motion and steps, and feeds the data to the built-in iOS 8 Health app. A number of apps in the App Store also access this same data.
Apple’s soon to be released Apple Watch also includes a built-in accelerometer, and will have the capability to track steps and body movement.