EDWARDSVILLE- In a first of its kind long-term study on the accuracy of popular activity bands, like FitBit and Jawbone, researchers at Southern Illinois University Edwardsville discovered some of the most popular brands overestimate the number of steps a person takes in a day.

SIUE Kinesiology Professor Bryan Smith and former student researcher Kristin Dierker, studied four of the most popular activity tracking devices during the 2013-2014 academic year to answer that question.

Contrary to other research on this topic that measured only short-term accuracy, Smith and Dierker examined how well the devices measured daily activity for a full week.

"People wear these for 24 hours a day, seven days a week, and no one else had asked the question: How accurate are these devices over the course of the day?" Smith explained.

Smith and Dierker's research analyzed what they considered the four most popular devices at that time: Nike FuelBand, FitBit One, FitBit Flex and Jawbone UP.

Nearly 40 participants wore each of the four activity monitors at the same time. Three were worn on the wrist. The FitBit One was worn on the waist, along with an ActiGraph GT3X+. The Actigraph is a research grade accelerometer that also measures steps. It was used as the standard for comparing the data collected.

Findings indicated two of the four devices were fairly accurate in their measurements. However, the other two greatly overestimated the participant's data.

"The Nike FuelBand, worn on the wrist, and the FitBit One, worn on the waist, had the best agreement with the Actigraph," Smith said. "On average, the Nike FuelBand was better than the FitBit One. The other two were not as accurate. They weren't very good at all."

Smith attributes the difference in devices to their sensitivity. He noted that both the FitBit Flex and Jawbone UP measure movement during sleep, while the Nike FuelBand does not. Smith believes that sensitivity caused the two devices to pick up extraneous movements of the upper body, leading to overestimated results.

Despite inaccurate measurements on some devices, activity trackers are still worth using, according to Smith.

"I think they're definitely worth it," Smith said. "Are they 100% accurate? No, they're not. But, if it motivates someone to be more physically active over the course of the day, I think it's doing its job."