Many fitness trackers measure health data such as your heart rate and number of calories burned, but can you really trust the information these devices provide? In a new study, researchers sought to find out
The result? Your fitness tracker may do a good job of measuring your heart rate, but you may not want to trust its readings showing how many calories you're burning.
In this study, researchers tested heart rate and calorie measurements from seven popular fitness trackers: the Apple Watch, Basis Peak, Fitbit Surge, Microsoft Band, Mio Alpha 2, and PulseOn Samsung Gear S2. They analyzed information from 60 volunteers who walked, ran on a treadmill or riding a stationary bike while wearing up to four fitness trackers. They then compared the trackers' data with data from standard medical devices that scientists use to measure people's heart rate and calorie burn in health studies.
The fitness trackers' heart rate measurements were very accurate: six of the seven fitness trackers dropped by less than 5 percent most of the time when they measured people's heart rates while riding stationary bikes, compared with medical-grade electrocardiographs, which the researchers say are the "gold standard" for measuring heart rate.
Heart rates measured while people were walking were higher than those measured while people were walking. Heart rates measured while people were walking were slightly lower than those measured while people were doing other activities, but the readings were still acceptable, the researchers said. Three of the trackers had heart rate measurements below 5 percent, and the rest below 9 percent, the researchers said. [Top 10 Surprising Facts About Your Heart]
In contrast, the trackers did not measure the number of calories people burned nearly enough. Compared to the gold-standard instrument for measuring calories burned, the most accurate instrument was off by about 30 percent, and the least accurate instrument was off by 93 percent, the researchers said.
"The heart rate measurements were far better than we expected," said researcher Euan Ashley, a professor of cardiovascular medicine, genetics, and biomedical data science at Stanford, in a statementBut the measures of energy consumption fell far short of the goal.
Stanford cardiology researcher Euan Ashley and his team used special equipment to test the accuracy of fitness trackers. (Paul Sakuma/Stanford University School of Medicine)Overall, one device was the most accurate - the Apple Watch, which tended to have the lowest measurement error, compared with the other six devices tested
The researchers concluded that people using fitness trackers could rely on the heart rate measurements they read on the devices, but not on the estimates of calories burned.
The researchers aren't sure why the calories-burned estimates are so inaccurate. But the fitness tracker's algorithm for calculating energy expenditure likely makes assumptions that don't necessarily apply to everyone, they said.
"It's difficult to train an algorithm that can be accurate across a variety of populations because energy expenditure is variable," based on a person's fitness level, height weight, and other factors, said researcher Anna Shchebina, a graduate student at Stanford University.
The researchers plan another study to examine the accuracy of fitness tracker measurements under out-of-laboratory conditions; they will have participants wear the trackers in their daily lives.
The study was published online today (May 24) in the Journal of Personalized Medicine.
It was the original article on life sciences.