• Fitness Trackers: Good at Measuring Heart Rate, Not So Good At Measurin

    From a425couple@21:1/5 to All on Fri Jun 2 19:15:00 2017
    Fitness Trackers: Good at Measuring Heart Rate, Not So Good At Measuring Calories

    Listen· 3:21

    Patricia Neighmond

    Researchers had participants wear the fitness trackers while walking or
    running on a treadmill and while riding an exercise bike to determine
    how well the trackers measured heart rate and energy expenditure.
    Paul Sakuma/Courtesy of Stanford University School of Medicine
    Sleek, high-tech wristbands are extremely popular these days, promising
    to measure heart rate, steps taken during the day, sleep, calories
    burned and even stress.

    And, increasingly, patients are heading to the doctor armed with reams
    of data gathered from their devices. "They're essentially asking us to
    digest the data and offer advice about how to avoid cardiovascular
    disease," says cardiologist Euan Ashley, associate professor of medicine
    at the Stanford University Medical Center and Stanford Hospital and
    Clinics in northern California. And, being somewhat near Silicon Valley,
    he says he gets a lot of tech-savvy patients bringing fitness-tracker
    data to appointments.

    The problem, he says, is that he just didn't know how reliable that data
    was. So, he and colleagues decided to study seven of the most popular
    devices and compare their accuracy to the gold-standard tests that
    doctor's use.

    They looked at two metrics: heart rate and calories burned. For heart
    rate, the fitness trackers were compared to findings from an electro-cardiogram, or EKG. It turned out the devices were "surprisingly accurate", says Ashley. "Most devices most of the time were 'off' by
    only about 5 percent."

    However, when it came to measuring how many calories a person burned,
    the findings were way off, says Ashley, showing a degree of inaccuracy
    that ranged from 20 percent to 93 percent, meaning 93 percent of the
    time the worst-performing device was wrong. Researchers compared the
    findings of the wrist devices to a sophisticated system of calculating metabolism which measures oxygen and carbon dioxide in people's breath.

    "This is a very well-designed and well-done study," says Dr. Tim Church,
    a professor of preventative medicine at Pennington Biomedical Research
    Center at Louisiana State University who was not involved in the study.
    Church routinely consults with companies about how to introduce wellness strategies into the workplace. Being wrong 93 percent of the time means
    the findings from the fitness tracker are more "fiction than fact," he
    says, which can actually undermine a healthy diet. "It's just human
    nature. People are checking these inaccurate counts and they think
    they've earned a muffin or earned some ice cream and they're sabotaging
    their weight-loss program."

    Church points to a study last year which found participants in a
    weight-loss program who also wore fitness trackers actually lost less
    weight than participants who didn't wear the trackers. "It's an instance
    of no information is probably better than having bad information," he says.

    The Stanford study was published in the Journal of Personalized
    Medicine. It was relatively small, with 29 men and 31 women. In addition
    to the primary results, there were some other interesting findings. In
    certain groups of people — for example, those with darker skin, higher
    BMIs and men — the error made by devices was actually greater than for Caucasian women with a more healthy weight.

    Researcher Euan Ashley and his team in a testing lab at Stanford
    University School of Medicine.
    Paul Sakuma/Courtesy of Stanford University School of Medicine
    "So, for those for whom it might matter the most, who are trying to lose weight, the error was actually greater," says Ashley, who doesn't know
    why this may be the case. He speculates that it could be that companies
    use a fairly narrow group of people for testing the equations they use
    to measure heart rate and calories burned.

    The study didn't look at how well devices count steps or monitor sleep
    or stress. The take-home message, says Ashley, is to not rely on the
    devices to measure total calories burned. Instead focus on eating what
    we know is a healthy diet, which is low in sugar and high in fiber, and
    to "eat not until you're full but until you're no longer hungry."

    And, of course, people should exercise, he says, adding, "we have no
    more important intervention than exercise for the prevention of any
    number of diseases."

    Makers of two devices, Fitbit and PulseOn say they remain confident in
    the performance of the trackers both in measuring heart rate and
    calories burned. In a statement, PulseOn questioned the study's
    methodology, saying that the high errors for calorie measurements
    "suggest that the authors may not have properly set all the user
    parameters on the device."

    Mark Gorelick, the chief science officer at the device-maker Mio Global,
    says, "we agree that more accurate calorie estimation is important for
    the industry as a whole, since most individuals are monitoring calorie
    deficits for weight loss." The other device makers did not immediately
    respond to requests for comment.


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