According to a recent study published by researchers from the Stanford University, wearables do well in measuring heart rate but all perform in an inaccurate manner when counting burned calories. The study focused on seven wearables that claim they can measure both heart rate and calories burned – the Apple Watch, Samsung Gear S2, Basis Peak, Fitbit Surge, Microsoft Band, Mio Alpha 2, and the PulseOn. Those wearables were used by 60 subjects, of which 31 were male and 29 female. All of the subjects measured their heart rate and the total amount of burned calories using wearables and standard medical instruments after running on a treadmill and riding an exercise bike.
The study saw that wearables underperformed in terms of measuring energy expenditure, which is more commonly known as the total amount of calories burned. The researchers saw massive differences between the measurements of wearables and the standard medical instruments used for determining energy expenditure, with the most accurate wearable seeing measurement errors of 27 percent. Meanwhile, the worst performing wearable was off by as much as 93 percent from the data collected by the medical instruments. The researchers think that the main cause for these erroneous measurements is the incorrect assumptions made by algorithms that measure energy expenditure. The wearables use algorithms to calculate the total number of calories burned and in order to determine the desired value, the algorithms make assumptions about the fitness level and body characteristics of individuals using them. Given the wide range of different types of individuals using wearables, it can be difficult to develop an algorithm that is suitable for everyone, as evidenced by this study.
The tested devices were able to properly measure heart rates, with error rates that are much lower than the standard 10-percent threshold for erroneous measurements. Six out of the seven wearables tested were able to determine heart rates within a five-percent error rate. The researchers pointed out that the accuracy of heart rate measurements may simply depend on the sensors used by the device. Given the research group's findings on inaccurate energy expenditure measurements, the group is emphasizing the need for a more open and transparent evaluation of wearables. By opening up the evaluation process, consumers can be more informed about what wearables suit their needs and body types, the researchers believe.