Step It Up and Go
All about fitness trackers in 3,969 steps: our author treks across campus to learn more about a UMass Amherst study on the precision and accuracy of consumer activity trackers.
I’m playing in my regular Monday night tennis game with a Fitbit, an Apple Watch, a Garmin Vivofit, and 11 other activity trackers around my wrists, waist, and ankle. As I race toward the net for a drop shot, I almost trample a UMass student research assistant who is recording my moves with a GoPro camera. I’m frustrated when I miss the drop shot, but think, “At least I got my step count up.”
The video of my clumsy tennis is part of a UMass Amherst study on the precision and accuracy of consumer activity trackers. Decades before millions of people bought personal activity trackers, UMass kinesiologists were working with research-grade trackers to study activity and health and investigating the trackers themselves. UMass has been on the forefront of such research, using trackers to study everything from cardiovascular rehabilitation to sitting habits. What can the global experts at UMass teach new tracker-wearers and the step-obsessed about our activity monitors? Are they accurate? Can they help us become more fit? Will taking 10,000 steps per day make you healthier? Should you walk faster? And what kind of activity trackers will we wear in the future?
Starting at Munson Hall with a Garmin Forerunner on my wrist, I set off around campus to find out.
Patty Freedson, longtime professor of kinesiology and activity tracker pioneer, was just weeks from retirement when I sought her out in the gleaming new Life Science Laboratories (1,054 steps from Munson and 40 steps up to Room 325.) Having worked with trackers since the mid-1990s, when pedometers were paramount, Freedson was not surprised to see consumer trackers like Fitbit take off soon after they were introduced, about seven years ago.
“The accelerometer used in activity trackers is the same type of device that is used in air bags and video-game consoles,” Freedson explains. “As more were produced, the cheaper they became. At the same time, public health awareness of the importance of physical activity for health has been increasing. Cell phones are now minicomputers capable of running sophisticated apps for trackers. These factors came together and sent sales of activity monitors skyrocketing.”
Don’t expect your Fitbit to drive behavior change—wearing the device won’t make you walk more—look at it as a facilitator of change.Patty Freedson
Like those of us who fret about being shortchanged on our daily step counts, scientists like Freedson are concerned about the reliability of consumer activity monitors. “We need more evidence, not just that they measure what they say they are going to measure, but just as importantly, how well do they detect change?” she says. Each tracker manufacturer uses proprietary algorithms to measure activity; few independent studies have tested their claims.
“Your activity tracker is only as good as its algorithms,” says Freedson. She’s excited about new algorithms being developed by interdisciplinary teams of UMass researchers in the Center for Personalized Health Monitoring, a component of the Institute for Applied Life Sciences (IALS). For example, Freedson is working with John Sirard, assistant professor of kinesiology, and John Staudenmayer, professor of math and statistics, who have a $2.2 million grant from the National Institutes of Health to develop more accurate methods to measure children and adolescents’ physical activity.
Freedson leaves me with a bit of wisdom: Don’t expect your Fitbit to drive behavior change—wearing the device won’t make you walk more—look at it as a facilitator of change. In other words, use the data it collects to guide your activity and keep you interested in your own fitness. She then directs me 14 steps down the hall of the Life Science Laboratories building to learn about a current UMass study certain to draw attention from those both inside and outside kinesiology.
Based in Room 314, PhD candidate Albert Mendoza and his student research assistants are conducting a comprehensive study of the precision and accuracy of activity trackers in the real world. “A lot of people are using these things, and we want them to have some measure of faith that what they are using is accurate,” Mendoza says. “No one yet has done the research the way we’re doing it—outside of the lab and with many different devices.” He and his team are looking at how well 14 widely available activity monitors measure everyday activities, what kinesiologists call “free living.”
Mendoza will outfit 32 adults with activity monitors and videotape them riding bikes, watching Netflix, baking cookies, grocery shopping, and more. After the taping, a student researcher will watch the video and laboriously chart the subject’s activity—hand counting steps and coding other movements. They will then compare the directly observed data with data from the 14 monitors.
Mendoza is looking for research subjects, so I sign on. Over the next few weeks, his crew monitors my steps while I wear 14 trackers simultaneously for three two-hour research sessions—on a typical morning at the office, on the tennis court, and on a weekend hike. When the research is complete, we’ll know the truth behind anecdotal evidence suggesting that fitness trackers are better at slower speeds and at counting forward and back steps than other movement, and that waist-worn monitors are more accurate than those worn on the wrist. (The results of the study will be available this summer at umass.edu/magazine.)
Illustrations by Donough O’Malley