Study shows measuring caloric with wrist-worn devices not accurate

May 29, 2017
The researchers note in their introduction that although physical exercise is proved to have a positive effect on coronary heart disease, responsible for one in every four deaths in the U.S., not enough knowledge has been gathered on the benefit of documenting exercise time and calorie expenditure on health. Wrist-worn devices have become a popular method of collecting a lot of data, fast. However, how accurate are these wristbands exactly? The researchers aimed to define how accurate these devices are when measuring physical activity. The study was carried out among sixty participants, 29 males and 31 females.

Seven wristbands studied

The researchers chose a diverse group of participants, selecting people of different ages, height, weight, body mass index, wrist circumference, and fitness level. The seven wristbands used were Apple Watch, Basis Peak, Fitbit Surge, Microsoft Band, MIO Alpha 2, PulseOn, and Samsung Gear S2. These are all commercially available and worn on the wrist.

The participants were measured while sitting, walking, running and cycling, all the while wearing up to four wristbands. Simultaneously, the participants underwent electrocardiographic monitoring, which is the most commonly used way to measure the activity of the heart. The metabolic rate was additionally measured with an instrument for measuring the oxygen and carbon dioxide in breath.

Caloric burn measurement not accurate

After analysing all the collected data, the researchers came to the conclusion that the devices were pretty much up to standard when it came to measuring heart rate. Across all devices and activities, the Apple Watch came out on top: it had the lowest error. All devices had the lowest error when measuring heart rate during cycling. Walking has the highest error.

However, when measuring energy expenditure, the devices did not fare as well. The Fitbit Surge did best with an average error rate of 27.4%. PulseOn turned out the be the least accurate device with an average error rate of 92.6%, which means it was wrong about caloric burn almost every time. The error rate for males was higher than for females across all devices.

The researchers are not entirely sure as to why energy expenditure seems to be so hard to measure. It might have something to do with the incorporation of someone’s height, weight and energy levels in an algorithm. The researchers do think that consumers and practitioners should be more aware of the inaccuracy of these wristbands. They encourage transparency from device companies surrounding these measurements.