Fitness tracker: good at measuring heart rate, not good at measuring calories.


The researchers asked participants to wear fitness trackers while they were running or running on a treadmill, while riding a stationary bike to determine the rate of heart rate and energy expenditure.
These trendy high-tech wristbands are so popular that they promise to measure heart rate, daytime steps, sleep, burning calories, and even stress.
And more and more patients are taking large amounts of data collected from their devices to hospitals. “They are essentially required us to digest the data, and provides the suggestion on how to prevent cardiovascular disease,” Stanford university medical center and northern California associate professor of medicine at Stanford hospital and clinic Euan Ashley said. And, near silicon valley, he says he gets a lot of tech-savvy patients to bring fitness tracking data into his appointments.
The problem, he says, is that he just doesn’t know how reliable the data is. So he and his colleagues decided to study seven of the most popular devices and compare their accuracy with the gold standard test used by doctors.
They looked at two indicators: heart rate and calories burned. For heart rate, the fitness tracker was compared with the ecg or EKG findings. The devices proved “very accurate,” Ashley said. “Most devices are only about 5 percent of the time.”
However, in the measurement of a person how many calories burned, Ashley said disappointing results, showing a certain degree of inaccuracy, ranging from 20% to 93%, that means 93% of the worst performing equipment made a mistake. The researchers compared the discovery of wrist devices with the metabolic system that measures oxygen and carbon dioxide in people’s breath.
“This is a well-designed, do a very good research,” Louisiana state university professor pennington biomedical research center of preventive medicine, said Dr Tim church, who was not involved in the study. Churches often negotiate with companies on how to bring health strategies into the workplace. Ninety-three percent of the time errors mean that fitness trackers find more “fiction than fact,” which, he says, may actually harm a healthy diet. “This is just the human nature, people are checking these inaccurate figures, they think they’ve got a muffin or won some ice cream, and is destroying their weight loss plan.”
A study published last year by Church found that participants who also wore fitness trackers actually lost significantly more weight than those who didn’t. “This is an example without information, probably better than having bad information,” he said.
The Stanford study was published in the journal of personalized medicine. This is relatively small, with 29 men and 31 women. Besides the main results, there are some interesting findings. In some groups – such as those with darker skin, higher BMI and more men – the errors in equipment were actually greater than those of healthy white women.
Researcher Euan Ashley and his team work at the testing laboratory at Stanford university school of medicine.
“So, for the most important people, who is trying to lose weight, the mistake is actually bigger,” said ASHLEY, who doesn’t know why. He speculated that it might be because the company used a rather narrow group of people to test the equations they used to measure heart rate and burn calories.
The study did not consider how the devices calculated steps or monitored sleep or stress. ASHLEY says the message of the interview is not to rely on these devices to measure the total calories burned. Instead, focus on eating what we know is a healthy diet that is low in sugar, high in fiber and “only eaten when you’re full but not hungry anymore.”
And, of course, people should exercise, he said, adding, “we have no more important interventions than preventing any disease.”
Makers of devices like Fitbit and PulseOn say they remain confident in tracking their heart rate and burning calories. In a statement, PulseOn challenged the study’s methodology, saying that high calorie measurement errors “indicate that the author may not have correctly set all user parameters on the device.”
Equipment manufacturers benefiting from Global chief scientific officer Mark Gorelick, said: “we agree that more accurate calorie evaluation is very important for the industry as a whole, because most people are in monitoring defects of calories to lose weight.” Other device makers didn’t immediately respond to requests for comment.