The Accuracy of Fitness Trackers Varies with Their Location on the Body (P16-019-19)

Abstract

ObjectivesAdvances in low cost physiologic monitoring devices have led to the possibility of making objective measures of physical activity in clinical practice. In a previous study, total daily step counts measured by a pedometer were lower than those obtained from a smartphone application, while exercise step counts were similar. It is uncertain which is the more accurate value for total daily steps. Most pedometers are worn on the torso while most fitness trackers are worn on the wrist. Overestimation of daily step counts by wrist-worn fitness trackers have been demonstrated by others.Specific aims: To estimate the precision of pedometer step counts measured during a 400 m walk. To compare daily step counts using a pedometer on the torso and fitness trackers worn on the wrist or on the torso. MethodsSix subjects wore a pedometer (Omron Alvita HJ327T) and an activity monitor (Letscom Fitness Tracker ID130Plus ColorHR). Each subject wore the pedometer on the torso and two activity monitors for 3 days; both activity monitors on one wrist, one activity monitor on a wrist and the other on the torso (belt), and the reverse positions of the activity monitors. In addition, each subject completed a 400 m walk on two occasions and walked a total of 500 counted steps. Total and 400 m step counts for the pedometer and activity monitor and the test/retest results during the 400 m walk were compared by paired T test and inter-individual variations were compared by one-way analysis of variance (ANOVA). ResultsPedometer-measured and counted steps differed by 1%. Test/retest pedometer step counts and times to completion for the 400 m walk both differed by 1.4%. Wrist-worn fitness trackers produced higher step counts than did the pedometers (18.6 + 0.18%, P < 0.002). Fitness trackers worn on the torso gave lower step counts than did the pedometer (−9.2 + 0.08%, P < 0.001). The inter-individual differences were not statistically significant for wrist or torso step counts. ConclusionsA pedometer worn on the torso is a precise measure of step counts during a 400 m walk and accurate compared to counted steps. Wrist-worn fitness trackers overestimate total daily step counts, at least compared to a pedometer. The location of the fitness tracker on the body greatly influences its estimation of total daily step counts. Funding SourcesDiscretionary funds.