Yes, Fitness Bands Are Imprecise. So What?

Now that fitness bands are officially a thing, they’re starting to come under new scrutiny. I keep reading these technology blogs where somebody thinks it’s an ingenious experiment to wear several different bands simultaneously — and then to cluck about how different their step counts are at the end of the day.

(Getty Images)

“The Fitbit Flex registered 7,225 steps for my day, while the UP band registered only 7,095,” you might read. The message: Clearly, these are inaccurate toys. Buyer beware.

In fact, my previous employer, The New York Times, posted a fun, visual exposé of these fitness bands’ inaccuracy. Check it out here.

A fitness band contains an accelerometer — basically a three-dimensional motion sensor. It detects the swinging of your arms and concludes that you’re walking.

But as The Times’ graphic points out, you can fool it in all kinds of ways. You can deadlift a barbell, which certainly should count as exercise, but since the band doesn’t detect arm-swinging, it thinks you’re sitting still.

You don’t get any credit when you’re riding a bike, either, or even when you’re swimming, because the band isn’t seeing the usual arm-swinging motion.

Yet when you’re repetitively stuffing Doritos into your mouth, guess what? Then you get step credit.

Well, these all make good stories for a news cycle or so. But all of it misses the point.

Yes, different bands may give you different step tallies for the day. But the purpose of this kind of product isn’t to record exactly how many steps you take — it’s to motivate you to take more. It’s to meet your goals. Earn those badges. Show off improvement to your social network.

It wouldn’t matter if your fitness band tracked steps or bananas or Scotch-tape dispensers; the point is to rack up more than you’re doing now.

And in that department, these bands do an excellent job. I’m the classic customer: I genuinely do walk more, park farther away, opt for stairs instead of escalators or elevators. I’m much more aware of how well I’m sleeping, too, and I make an effort to do better. The silicone band on my wrist truly has made me healthier. And I’m not alone.

Until you’ve tried one, I realize that it sounds absurd: “Yes, we all know that more exercise is better — why do I need a gadget for that?”

But trust me. Something about seeing it on your wrist and on your phone puts it front of mind. It makes a difference.

I once read about a study involving thermostats that displayed not just the temperature but also the dollars a day a homeowner was spending on heat at that temperature. Those homeowners wound up using a lot less heat than regular thermostat owners. Same idea.

Shamed into shape
One reason the bands work so well is that you can, at your option, share your achievements with friends and family over the Internet. Their phones show not just their own activity, but yours, too. There’s a subtle competition aspect that, once again, motivates you.

But in that case, you’re competing — doesn’t the difference in step-counting accuracy matter in that case?

No, because you can share your data only with people who own the same brand band that you have. Your UP band steps are the same as your buddy’s UP band steps, even if they don’t correlate with a Garmin band owner’s steps.

And then there’s sleep monitoring.

The UP band shows you a very cool graph that pinpoints what happened during your night of sleep: how long you were in deep sleep, how long you were in light sleep, and how many times you awoke.

Of course, all it has to go on is what movements your wrist makes; it doesn’t have wires connected to your brain. Its software assumes that if you’re lying very still, you’re probably sleeping deeply. If you’re making a lot of movement in a very short time, you probably woke up. And so on.

You’re only cheating yourself
This, too, has skeptics crying foul. “That’s just an interpretation!” they complain. “I could take the band off and leave it on my nightstand, and it would record a night of very deep sleep!”

Well, yes, you could do that. If you’re a nutjob.

The unscientific basis of those graphs is causing some pushback. A recent UP band software update changed the name of the stillness phase from “Deep sleep” to “Sound sleep,” precisely to calm down the sticklers who point out that there’s no way the band could know what your brain is actually doing.

Some bands, like the Garmin, don’t make an attempt to interpret your motion. They just show you a graph of your movements during sleep. Which, really, isn’t useful at all. In their attempt to be technically correct, the software designers have removed almost all meaning from this feature.

The Samsung Gear Fit offers both. It shows you a movement graph and attempts to summarize your night:

The bottom line: People, lay down your swords. These devices will not be hooked up to NASA astronauts to monitor their vital signs. These will not be put on intensive-care patients. We can all agree that these fitness bands are not medical devices (as the Samsung software warns you so often that it becomes absurd).

They’re motivational devices. They call your attention to the amount of time you spend sitting motionless, and to how dangerously little good sleep you’re getting, and they inspire you to do something about it.

And in that regard, they work.

More of them, please, on the wrists of more people!

You can email David Pogue here.