Researchers from Stanford University, California, and the Swedish School of Sport and Health Sciences in Stockholm, Sweden recently laboratory tested the accuracy of seven commercial wristband devices. They noted that for all these devices, energy expenditure is measured indirectly through surrogate calculations and varies based on fitness level and factors related to your body dimensions. Among those tested, the most accurate device, the Fitbit Surge, still had a median error rate for energy expenditure across tasks of 27.4%; 95% CI, 24.0%-30.8%. This means that the consumer should expect that these devices’ output error to be substantial. In fact, the performance by the PulseOn device demonstrated an error rate of approximately 92.6%; 95% CI, 87.5%-97.7%. On the basis of these findings, it is easy to conclude that most wrist-worn devices poorly estimate energy expenditure. Moreover, each device manufacturer has its own proprietary algorithm for calculating energy expenditure. So, you cannot even compare outputs against each other, rather only against itself or a selected standard, as persons wearing different manufacturers’ devices are producing “apples versus oranges versus bananas…etc.” data even if they are alleging to measure the same thing.
By analogy, another simple device with which many are familiar is the pedometer. These portable tools measure steps/strides, distance and time spent walking, jogging, or running. Available models are too numerous to count, may be expensive or very cheaply made, and they are exceedingly variable in levels of sophistication in construction and apps included. As such, depending upon the quality of the device, you may be challenged when using it to compare even your own performance trends because the devices frequently underperform consumer expectations.
Most personal exercise monitors exhibit problems with accuracy, precision, and reproducibility in measurement. Still, any efforts to stretch, strengthen and increase your heart rate as you engage in exercise is a healthy activity. ISG Health opines that if using wrist monitors or other exercise monitoring devices encourages you to exercise more regularly, use them. Your fitness matters – good health matters.