Will Your Activity Tracker Make You Want to Exercise?

Mature woman checking activity tracker outside
Betsie Van der Meer/Getty Images

If you've resolved to slow down your biological clock by sitting less and moving more in the months ahead, you might be considering an electronic activity monitor to help you stay motivated. These wearable devices track everything from the time you spend sitting or standing to your sleep patterns. But do they actually make you more active?

The short answer is, there's been little research on whether high-tech activity monitors motivate more movement in the people who wear them.

How They Work

Old-style pedometers use a simple lever mechanism which activates a switch each time you take a step. Though they may lose accuracy over time, they generally offer a precise reading on the number of steps taken by the wearer. Any readout of calories burned, or distance traveled, is extrapolated from stride length and the number of steps the pedometer tracks.

The new generation of activity monitors flooding the market since the early 2000s uses more advanced technology to track your movement in three dimensions. Employing a three-axis accelerometer, these devices can detect any motion, rather than just steps forward (or backward) during walking or running.

Risks of Too Much Sitting

The dangers of being too sedentary have led some researchers to coin the term "sitting disease." A 2012 study on more than 220,000 Australian adults, published in the Archives of Internal Medicine, found that prolonged sitting is a significant risk factor for death from any cause.

Mounting evidence suggests that a sedentary lifestyle contributes to many age-related diseases, such as heart disease and diabetes.

There's also a growing appreciation for the health benefits and potential calorie burn of daily movements of any kind. For example, Mayo Clinic researcher James Levine has written extensively about "non-exercise activity thermogenesis" (NEAT), which refers to the energy expenditure in simple actions like standing, walking slowly, or even fidgeting.

How Accurate are the New-Generation Activity Monitors?

Not much research has been conducted on the accuracy of accelerometer-based activity trackers. 

A few small studies published in 2013 compared some commercially-available electronic trackers like the Fitbit with data from a room calorimeter on calories burned and with treadmill readings on steps taken and distance traveled. All the studies found the devices mostly accurate for step counts, but much less so for other data: the first-generation FitBit monitor was found to underestimate energy expenditure by almost 30%, for example.

In a second study assessing the accuracy of the Fitbit One - in which each subject wore three identical trackers while walking on a treadmill - step counts were found to be consistent between all devices. There was more than 39% relative error in the distance readings, however (meaning the readings were off by over 39%). This error prompted the researchers to suggest users disregard distance information.

But How Motivating are They?

High-tech trackers have yet to be assessed for their power to motivate us off our couches. Anecdotally, many people who like them report that the devices are highly motivating, even addictive.

Anne Thorndike, an assistant professor of medicine at Harvard and an associate physician at the Harvard-affiliated Massachusetts General Hospital, has researched activity trackers. She tells me that determining whether monitors actually motivate more movement is a fundamental question.

"This is the big issue," she says. "Do they motivate people who aren't yet motivated? Or do they just prompt people who are already motivated to be active each day? And beyond that, do the people who buy them continue to be motivated over time? In the end, you're either exercising or you're not."

In 2014, Thorndike published a study using activity trackers on medical school residents over a 12-week period. During the second half of the study, which featured a team steps competition, residents recorded more average steps per day than they had before. However, they also had more "noncompliant" days in which the trackers recorded fewer than 500 steps. This may have been due to fatigue; that is, people may have found the feedback motivating at first but less so over time after the device lost its novelty.

Overall, she says, trackers may not be for everyone.

"I think people who love data and love feedback probably will really like these monitors," she tells me. "But the big question is whether they really work to get and keep people moving in the longer-term; there's been no systematic analysis of that yet."

In fact, Thorndike worries that the feedback on activity levels can actually demotivate users.

"If you've set yourself a goal, and the wristband is telling you every time you look at it that you haven't reached that benchmark, you may eventually just take the thing off."

Step Count May Be All You Need

Finally, a 2007 study on simple step-counting pedometers offers clues about the motivational power of a wearable monitor. Researchers from Stanford University's School of Medicine and elsewhere analyzed 26 different studies involving more than 2,700 participants, concluding that using a pedometer for an average of 18 weeks led to significantly more physical activity, lower blood pressure, and lower body mass index (BMI). The benefits were greatest for subjects who set a daily step goal (eg 10,000 steps).

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