Smart watches called useless for measuring heart rate
Oleg Lischuk, N+1
American scientists have come to the conclusion that fitness bracelets, including smart watches, do not have the necessary accuracy when measuring the pulse. The results of the work are published in JAMA Cardiology (Wang et al., Accuracy of Wrist-Worn Heart Rate Monitors).
In recent years, smart bracelets and watches have become increasingly popular among sports and fitness enthusiasts. They are able to monitor sleep, calorie consumption, physical activity, steps taken, but one of the main indicators that they focus on when dosing physical activity is the pulse rate. At the same time, no serious verification of the accuracy of the measurement of this indicator has yet been carried out.
Employees of the Cleveland Clinic Cardiovascular Institute analyzed the accuracy of optical heart rate monitors built into Fitbit Charge HR, Apple Watch, Mio Alpha and Basis Peak. To do this, they invited 50 healthy volunteers (average age 37 years) with normal body weight and measured their pulse using these devices at rest, during physical exertion of varying intensity (walking on a treadmill at different speeds) and during recovery. In parallel, the heart rate was recorded using an ECG and a Polar H7 chest electrode monitor. The measurement data covered the pulse rate from 49 to 200 per minute.
It turned out that Basis Peak overestimates the heart rate at moderate loads (the median discrepancy with ECG is 8.9 and 7.3 per minute at speeds of 3.2 and 4.8 kilometers per hour, respectively). Fitbit Charge HR, on the contrary, underestimated the value at intense loads (7.2 and 4.6 per minute at 6.4 and 9.6 kilometers per hour, respectively).
In general, 95 percent of the heart rate values measured using the Apple Watch and Mio Alpha were in the range of -27 to 29 per minute compared to ECG data. For the Fitbit Charge HR, this interval ranged from -34 to 39 per minute, and for the Basis Peak – from -39 to 33 per minute. Most precisely, these devices worked at rest. The chest monitor provided a much higher accuracy of readings. The body mass index, gender and age of the participants did not affect the measurement results.
Based on the results obtained, the scientists concluded that wrist optical devices do not provide satisfactory accuracy of pulse measurement. They can only roughly orient a person engaged in physical exercises, but they are not suitable for cardiac patients, since they can give them and their attending physicians false information.
"[Fitness bracelets and smart watches] cannot be used to diagnose or treat anything, you cannot rely on them in this context... If you use them and get an improbable pulse value, too high or low, do not worry – this is most likely a device error," explained one of the authors of the work, Marc Gillinov, in a telephone interview with Reuters.
The head of Fitbit's research partner Fitabase, Aaron Coleman, said that he did not consider the results of the study "too bad", given that amateur devices were compared with professional equipment. However, he admitted that the accuracy of measurements decreases as the sensor moves away from the heart.
Small successes of smartwatches in measuring the pulse do not prevent them from doing many other useful and not very things. For example, scientists were able to use them to determine the passwords and PIN codes entered by the owner, taught them to recognize objects in the hand, and also, using a smartwatch, placed the touch interface directly on the human skin and turned the finger into a handset. In addition, enthusiasts managed to download Windows 95 on similar devices and launch Counter-Strike.
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21.10.2016