Validation And Accuracy Of Fitbit Charge

Abstract

Introduction: Wearable physical activity (PA) monitors (e.g., Fitbit®) have become increasingly popular for both researchers and lay people alike. Recent studies have reported several Fitbit® models correlate with research grade monitors; however none have reported on the accuracy of Fitbit® devices. Furthermore, noneto date have examined the Fitbit® Charge model. Purpose: The primary purpose of this pilot study was to compare step counts assessed by Fitbit® Charge and a research grade accelerometer (i.e. Actigraph®). The secondary purpose of this pilot study was to compare minutes spent in each PA intensity (light, moderate, vigorous) assessed by Fitbit® Charge and Actigraph®.Methods: Participants (n=8) wore Fitbit® Charge and Actigraph® monitors for seven days. All analyses compared step counts and PA intensity assessed by both types of monitors. First, validity was examined through a series of bivariate correlations. Next, accuracy was investigated by a series of paired sample t-tests compared step counts and minutes spent in light, moderate and vigorous intensity activity assessed by Fitbit® and Actigraph® monitors. Results: Significant correlations were found for all study outcomes (p’s < 0.05). Significant differences were observed for step counts on all days and weekly total step count (p’s < 0.05). Significant differences were found on most days for light PA intensity (p’s < 0.05) and moderate intensity activity (p’s < 0.05), and one day for vigorous PA (p = 0.007). Overall accumulated weekly total of minutes were significantly different (p =0.014). Conclusions: Our results indicate that there are high correlations between Fitbit® and Actigraph®monitors. However, our examination of accuracy of Fitbit® Charge devices revealed that these monitors may overestimate step counts, light intensity PA, and vigorous intensity PA. Further research is needed to determine if Fitbit® Charge devices accurately assess PA. Thus, researchers should use caution if considering use of Fitbit® Charge.; ;