Stepping Stones

Can Fitness Trackers Really Track Your Fitness?

Is that electronic leash on your wrist really doing anything? Can you rely upon fitness trackers for good information? A pair of recent studies add to the reasons you might doubt it.

Heart Rate, Yes; Calories Burned, No

Researchers from Stanford tested seven fitness trackers and published their result in the Journal of Personalized Medicine. The list of devices covered a broad range: the Apple Watch, Basis Peak, Fitbit Surge, Microsoft Band, Mio Alpha 2, PulseOn, and Samsung Gear S2.

On estimates of calories burned, all seven devices flunked. Error rates ranged from 27% to 93%. They performed much better in estimating heart rate. The Apple Watch was most accurate, with a 2% error rate. The Samsung Gear S2 had the highest errors for heart rate. But even so, the error rate was less than 7%.

Counting Steps? Not on Your Wrist

In the International Journal of Exercise Science, researchers recently published a study of accuracy for different types of Fitbit trackers. They examined step counts in a controlled setting. They compared wristband trackers to trackers worn on your waist like an old style pedometer.

Worn on the waist, the trackers were accurate within 0.5% of actual step counts. On the wrist, they were off by 7-20%.

Stepping Back

Stepping back from all this detail, what have we learned?

These gizmos are surprisingly good for tracking heart rate. For tracking steps, don’t count on a fitness band for precision. They might be good enough to keep you motivated and moving, but that’s it.

For calories? Forget it. And besides, burning calories is not really the point of physical activity. The real benefit of physical activity is better health, not burning extra calories to lose weight.

When people get focused on burning calories through exercise, it often translates into permission to eat more calories. That might be why exercise is a lousy way to lose weight. And fitness trackers aren’t much help for losing weight either.

But then, for health, fitness is a worthy goal all by itself.

Click here for the study of calories and heart rate. For the study of step counts, click here. For an entertaining account by David Sedaris about becoming a slave to a Fitbit, click here.

Stepping Stones, photograph © Youn-Sik Kim / flickr

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May 27, 2017

2 Responses to “Can Fitness Trackers Really Track Your Fitness?”

  1. May 28, 2017 at 11:32 am, Ray said:

    In your article you say “That might be why exercise is a lousy way to lose weight” so then what is a better way to lose weight?

    • May 29, 2017 at 4:06 am, Ted said:

      A complete answer, Ray, would fill many books. The short answer is that changing what you eat is the most effective way to lose weight. And for the weight loss to be sustainable, the new pattern of eating needs to be sustainable. For this, a smart dietitian can be a big help.

      Exercise has many benefits. But weight loss is not one of them.