Commercial fitness trackers are being used for all kinds of things other than tracking steps.
They measure heart rate, track sleep patterns, and calculate basal metabolic rate and calories burned.
Theyre used in clinical trials, research labs, and by insurance companies and corporate wellness programs.
But are they really reliable enough?
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(Well get to that in a minute.)
Users can further personalize those calculations by programming the equipment with their height, weight, and age.
They do detect steps well if its normal paced steps, normal cadence, Feehan said.
They were designed to measure purposeful walking.
Theres a definite bias in there, she said.
How a child moves and how someone whos 90 moves is very different.
Fitbit declined to comment on individual studies.
If youre aiming for those mythical 10,000 steps a day, your count might be off.
Between beats, the blood ebbs away, absorbing less light.
From these measurements, the gadget then calculates heart rate.
But the green LED sensors that track heart rate can be unreliable.
Fitbit says the company has worked hard to calibrate the sensors in their devices to work for everyone.
Smartwatch maker Polar evenlists dark skin and tattoosas factors that can limit the accuracy of wrist-worn monitors.
The Apple Watch usesinfrared sensorsin addition to green LEDs to measure resting heart rate.
Even so, the accuracy of wrist-worn sensors varies a lot depending on the jot down of activity.
The more variation within our exercise, the bigger the difference, said Mattsson.
Calories: A most elusive metric
Heres where things get really murky.
But how many calories you burn during an activity is the most unreliable metric that fitness trackers calculate.
The engineers create algorithms for machines.
But humans are not machines, he said.
As with step counting, Mattsson said the problem lies in the algorithm.
Since they are using an algorithm and proxy measures, its never going to be perfect, he said.
The biggest problem is that theyve done the algorithms for a subset of people.
In most studies you talk about white males in their 30s at average fitness level.
The farther away you get, the bigger the risk of a problem.
Mattsson said the situation lands fitness trackers in an awkward Catch-22.
To improve, companies need a more diverse group of people to buy and use their product.
But then you need a lot of people to use them even if theyre not perfect, he said.
If youre looking to calorie count, dont rely on your fitness tracker.
This article wasoriginally published on The Markupand was republished under theCreative Commons Attribution-NonCommercial-NoDerivativeslicense.
