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March 2014 Article

Wearable technology — those wristbands, watches and belt gadgets that track your every move — hold tremendous promise for improving health and physical performance. But as often happens, the technology has outstripped the research, and scientists are still struggling to understand whether the monitors work as promised, how to keep people motivated to use them, and exactly what the devices are supposed to accomplish, anyway.

To measure the accuracy of activity trackers worn on the wrist or waistband, researchers from Arizona State University conducted two studies, with equivocal results. The research, presented last summer at the annual meeting of the American College of Sports Medicine, tested the devices against bulkier, high-tech masks placed over volunteers’ faces to measure oxygen consumption. These are considered the scientific gold standard for determining energy expenditure (if not for providing comfort, convenience or style).

After asking participants to engage in activities like exercise, playing games and housework, the researchers found that the trackers were able to record some but not all of the subjects’ movements. The devices reliably tracked forward motion; they counted how many steps volunteers took while walking or jogging, and accurately determined corresponding energy consumption.

But the trackers were inept at measuring volunteers’ more subtle movements, such as when they stood, played Scrabble, gently pedaled a stationary bicycle, or used a broom to sweep up around the physiology lab. Over all, the results suggest that consumer activity monitors “do not detect light-intensity activities very well,” said Glenn Gaesser, a professor and the director of the Healthy Lifestyles Research Center at Arizona State University, who oversaw one of the studies.

The devices rely on mathematical equations that “were developed using activities easy to measure, such as brisk walking or jogging,” he said.

Also, the Food and Drug Administration does not regulate these devices; no outside agency or reviewer vets their accuracy. But that seeming shortcoming may not matter to casual users.

“There’s a difference between accuracy and precision,” said Ray Browning, an assistant professor of exercise science at Colorado State University, who has been studying activity trackers for several years. Today’s models may not be especially accurate, he said; their numbers for energy expenditure would not jibe with those from sophisticated laboratory testing.

Plus activity trackers can’t promise to change behavior. “The motivation piece is the elephant in the room,” he said.

Today’s monitors often incorporate motivational components, including social networking and friendly electronic reminders from an integrated electronic nagger to get up and move. But to date, no long-term, peer-reviewed study has shown that people using activity trackers become and remain more active. And people can be complex and perverse fitness consumers.

“Suppose you’re having a terrible week at work,” Dr. Browning said. “You’re tired and overwhelmed.” It may well be that the last thing you’d want is a device telegraphing your sloth to a network of social acquaintances.

Notably, the trackers may be quite beneficial for a group of people who wouldn’t seem to need them: those who are already active and, in particular, athletes. A review of recent studies published in February in The Journal of Strength and Conditioning Research concluded that the use of GPS and heart rate monitors and similar technology by soccer, cricket, rugby and hockey players could result in “significant improvements in the preparation, training and recovery aspects of field-based team sports.”

Most of these monitors are unobtrusive, integrated into watches or athletic clothing, including shoes, shirts, socks and sports bras, “although we call them vests, for the sake of the guys” who occasionally must don them, said Lynda Ransdell, dean of the College of Education, Health and Human Development at Montana State University, who oversaw the review.

Using data from these devices, she said, coaches and athletes can plot precisely where each player is on the field during successful or feeble plays.

As it turns out, tech nudies — those of us who don’t wear any electronic devices — can gauge our workouts effectively without technology. Studies have shown that simply asking someone how hard they are exercising produces estimates nearly as accurate as measuring it. That’s because humans, unlike digital devices, are able to detect a unique mix of factors, including heart rate, oxygen consumption, muscular effort and mental fatigue “that technology cannot yet measure.” Yet.

The New York Times

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