When it comes to fitness trackers, the psychology behind them is just as important as the technology inside them.
Gadgets like the Nike+ FuelBand, Fitbit Ultra and BodyMedia Fit Link use accelerometers, altimeters and algorithms to track everything from how many steps you took to how many calories you burned. By providing this data instantaneously, and in some cases allowing you to share it via social media, they do more than inform. They reinforce, motivate and reward by turning exercise into a game.
Motivating couch potatoes and providing everyday athletes with data will be an increasingly lucrative business as so-called "wearable" computing devices like fitness trackers take off. Companies like Nike, Adidas and Motorola are expected to ship 90 million "wearables" by 2017, according to ABI Research.
Forrester Research is equally bullish, noting in a report this week that wearables are the "next wave of consumer technology product innovation" and companies like Adidas, Nike and Under Armour should work alongside the likes of Apple, Google and Facebook to maximise their potential.
How these devices work is a straightforward technological issue. Why they work delves into two important facets of activity: measurement and motivation. To know whether you're getting better at something, you need data. As physicist Lord Kelvin said, "If you cannot measure it, you cannot improve it." Once you've got data, you need specific goals or standards to provide the sense of accomplishment that will make you work harder.
One of the best things fitness trackers do is provide an objective measure of activity, said John Bartholomew, a kinesiology and health education professor at the University of Texas at Austin. The truth is, people are lousy at accurately judging their level of physical activity. Few people have any idea how many calories they've burned running for the train or walking to work. Others spend, say, half an hour on the treadmill each day and consider themselves "active." And still more promise they'll "get active" but fall short.
"By having this sort of equipment and this sort of technology, it allows you to actually track and look back to see how active you actually are," Bartholomew said. "You can't lie to yourself."
Once you've established an exercise routine and have a realistic idea of what you're doing each day, fitness trackers delve further into your psyche by motivating you. The routine things you do each day - climbing stairs, schlepping groceries, pushing the lawnmower - are cast in a new light. Suddenly, they're exercise. They always were, of course, but fitness trackers drive the point home by telling you just how many calories you burned raking the lawn. As a result, exercise becomes something you seek to interject into your life, a goal-directed activity that brings a sense of accomplishment. Every goal you reach - "Today I hit 12,000 steps!" - pushes you to do better next time.
"There's incredible power in knowing how you're doing," Stefan Olander, v.p. of digital sport at Nike, said in a discussion at South by Southwest. "It's inherently, incredibly motivational."
That motivation is amplified by the ability to broadcast your results via social media. Posting your stats to Facebook and Twitter lets you do more than boast. It allows others to encourage you or even join you in working toward similar goals like running a marathon. You're part of a community, which makes it that much harder to slack off.
Because these devices are so new (FitBit debuted in 2009, with the FitBit Ultra released in October 2011; the Nike+ FuelBand was announced in January), there's isn't a trove of research into their impact on exercise habits. But plenty of early adopters offer positive anecdotal evidence.
Tech blogger Louis Gray, a product marketing manager at Google, has detailed how "obsessively counting my steps, climbing the stairs and tracking how many miles I make on foot" has changed how he exercises. He found the stats and aura of competition attractive, and Fitbit's social element has pushed him to make healthier choices, much like Foursquare has encouraged him to try new things.
"It's the stinkin' badges - helped along by casual competition with friends, and now, despite my best attempts to not make any actual alterations to how I behave, I am sure I am doing things that are actually better for me," he wrote.
The ability to compare yourself with others via social media and track your progress with colorful graphs, charts and animations turn exercise - so often about repetitions performed, miles run, pace maintained - into a a game. Games are inherently fun, or we wouldn't play them.
In her book Reality Is Broken: Why Games Make Us Better and How They Can Change the World, game designer Jane McGonigal recounts how the game-like qualities of the Nike+ GPS running system immediately improved her running. The app's features, including real-time stats, a system of reward levels and personal achievements, "makes for a very good running game, one that uses better feedback and reward to help you put in a better effort and aspire to more than you would otherwise."
With the Nike+ GPS handling her fitness goals as she trained for a pair of half-marathons this year, McGonigal found the FuelBand created a surprising extra layer of goals. The wristband's system of NikeFuel points - which essentially assign a "score" based upon your daily activity - motivated her to find any excuse to keep moving.
"The points don't motivate me to get better at something - they just motivate me to not stand around or sit around so much," she said. "It disrupts your least active moments and makes you find ways to sneak in more activity."