A study has conducted a review of reports examining the reliability and effectiveness of Fitbit and Jawbone fitness trackers on estimating steps, distance, physical activity, energy expenditure, and sleep
Wearable activity tracker devices like Fitbits are useful for consumers who want to monitor their physical activity, optimize behaviours, and achieve health-related goals. Most devices enable the user to easily track their steps, distance travelled, and related personal data. However, how reliable and accurate are these trackers in doing so?
A U.S research group recently conducted a systematic review of 22 studies published since 2012 on the reliability and accuracy of popular activity trackers, including the FitBit Classic and Jawbone UP, and their ability to estimate steps, distance, physical activity, energy expenditure, and sleep. Fitbit and Jawbone trackers were accurate in counting steps when compared to pedometers and manual counting by the user, but tended to under-estimate steps at slow walking speeds. The step counts between individual Fitbit trackers were also very consistent.
The distance estimated between same-brand trackers were high, but the trackers were found to overestimate at slow speeds and underestimate at high speeds. In comparison to accelerometers, physical activity measurement of trackers generally over-counted moderate-to-vigorous physical activity, particularly evident with the Jawbone UP, FitBit One, and Zip. The reliability of these trackers in monitoring physical activity was not examined in any of the 22 studies reviewed.
Tracking sleep was reliable between similar trackers, however, they generally over-estimated total sleep time and in comparison to polysomnography, over-estimated sleep efficiency. Furthermore, calorimetry measurements revealed that energy expenditure was overall under-estimated by both FitBit and Jawbone trackers.
The research group suggest that FitBit, Jawbone, and other trackers should be documented prior to use in research studies and can be improved for accuracy by the general user if: 1) the tracker is worn in the same position every day, 2) personal details like age are entered into the application and synched with the tracker, 3) stride length is calibrated, 4) add-on features such as heart rate and respiration and sleep mode are used, 5) the app is updated when needed, and 6) information on specific physical activity is added to facilitate machine-learning.
Evenson, K.R., Goto, M.M, and Furberg, R.D. Systematic review of the validity and reliability of consumer-wearable activity trackers. International Journal of Behavioral Nutrition and Physical Activity, 12 (1), 2015.
Written by Fiona Wong, PhD