Activity Bands Can See You Run, But Not Deadlift

Bands are good at walking and running, but lose their accuracy for other types of exercise

Photo: Aaron Muszaklski

Activity trackers—those wearable bands that record the amount of exercise a person does each day—are becoming increasingly popular for both work-out fanatics and people looking to get in shape. But do they really work?

Researchers recently conducted two studies on the bands to quantify what they do and don't measure. They recruited volunteers to take part in a range of activities, The New York Times describes, including running, weight lifting, household chores and walking. The researchers used both activity trackers and scientific devices that measure a user's oxygen consumption—a proxy for how much energy a person is burning.

As the Times explains, an activity tracker relies on accelerometers to quantify exercise. "When still, it records only the force of gravity," the Times explains. "When moved, it records acceleration." So, the activity trackers excelled at recognizing when the user was walking or running. They could quanitfy the number of steps a person took and correctly calculate the energy expenditure those steps equated with. But, in other areas, the trackers fell short:      

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. 

The activity trackers didnt' do a good job, either, of recognizing if a user was undertaking relatively stationary but still energy-taxing activities, such as deadlifts or yoga. (Some of the technologies allow users to program their trackers to better recognize certain activities.) On the other hand, the Times adds, motions such as vigorously stuffing your face with potato chips might register as a calorie-burning session of bicep curls—as long as you're moving your hand fast enough.

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