For counting steps, smartphone apps do as well as fitness trackers

That's the conclusion from a University of Pennsylvania study, which compared the accuracy of fitness wristbands and of smartphone apps in counting steps.

Researchers gave participants an iPhone 5s running three fitness apps, a Galaxy S4 running one fitness app and six wearable devices, including products from Fitbit, Jawbone and Nike.

Next, the 14 participants walked on a treadmill while an observer counted the numbers of steps each person took. Fitness apps and tracker devices use step counts to calculate physical activity metrics like distance walked and calories burned.

The apps and the devices were similarly accurate. There was an average 7 percent discrepancy between the counts of the smartphone apps and the human observer, while wearable accuracy ranged between 2 percent and 20 percent.

Fitbit's One and Zip devices were the most accurate, while Nike's Fuelband fared the worst. Nike didn't immediately reply to a request for comment.

A motivation for the study is the scarcity of data about how accurate these apps and devices are at tracking physical activity, said Meredith Case, who co-authored the study. People must be able to trust the data if they're using it to make health decisions.

However, owners of wearable fitness trackers shouldn't feel remorseful over their purchase. Instead, they should "rest assured" knowing that most of the devices tested are properly tracking their workouts, she said.

Fred O'Connor writes about IT careers and health IT for The IDG News Service. Follow Fred on Twitter at @fredjoconnor. Fred's e-mail address is fred_o'connor@idg.com