An online search of trending Christmas gifts shows fitness activity trackers are what many want to find under the tree this year. Multiple companies promote their particular monitor as the most accurate when tracking a person’s activity. But are they as accurate at tracking daily steps and energy expenditure as claimed?
Southern Illinois University Edwardsville’s Bryan Smith, assistant professor of kinesiology and health education, 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. “Who cares how accurate they are when you’re on a treadmill. How accurate are they during activities of daily living?”
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.
“They were told to wear the monitors while they were awake,” Smith said. “Participants took them off when they exercised. I wanted measurements of activities of daily living only.”
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 the 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.
The question left to answer, according to Smith, is what is the variability of these monitoring devices?
“If a device is off by 1,200 steps per day, and it’s always off by that, I think that’s ok,” Smith said. “At least if there’s a change in physical activity you’ll be able to pick it up. But if it’s 1,200 high one day and 1,000 low the next, you really have no consistency.”
What do these findings mean for consumers in search of an ever-popular activity tracker this holiday season? Are they worth the cost?
“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.”
The market is now flooded with activity tracking devices, beyond those tested, with greater capabilities like interfacing with a heart rate monitor. Smith suggests considering the product’s usability and its applications when deciding which device to purchase. He notes that since this research was completed, the Nike FuelBand has been discontinued.
Dierker was an associate in SIUE’s Undergraduate Research and Creative Activities (URCA) Program. The internal program allows students to lead an independent project and manage the project budget with guidance from a faculty member.
The research conducted by Smith and Dierker was presented at the American College of Sports Medicine in May 2014.
Photo: Bryan Smith, assistant professor of kinesiology and health education.