Inter-Device Agreement between Fitbit Flex 1 and 2 for Assessing Sedentary Behavior and Physical Activity

Sunku Kwon, Ryan D. Burns, Youngwon Kim, Yang Bai and Wonwoo Byun
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Sunku Kwon: Department of Health and Kinesiology, University of Utah, Salt Lake City, UT 84112, USA
Ryan D. Burns: Department of Health and Kinesiology, University of Utah, Salt Lake City, UT 84112, USA
Youngwon Kim: School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong
Yang Bai: Department of Health and Kinesiology, University of Utah, Salt Lake City, UT 84112, USA
Wonwoo Byun: Department of Health and Kinesiology, University of Utah, Salt Lake City, UT 84112, USA

IJERPH, 2021, vol. 18, issue 5, 1-11

Abstract: This study examined the inter-model agreement between the Fitbit Flex (FF) and FF2 in estimating sedentary behavior (SED) and physical activity (PA) during a free-living condition. 33 healthy adults wore the FF and FF2 on non-dominant wrist for 14 consecutive days. After excluding sleep and non-wear time, data from the FF and FF2 was converted to the time spent (min/day) in SED and PA using a proprietary algorithm. Pearson’s correlation was used to evaluate the association between the estimates from FF and FF2. Mean absolute percent errors (MAPE) were used to examine differences and measurement agreement in SED and PA estimates between FF and FF2. Bland-Altman (BA) plots were used to examine systematic bias between two devices. Equivalence testing was conducted to examine the equivalence between the FF and FF2. The FF2 had strong correlations with the FF in estimating SED and PA times. Compared to the FF, the FF2 yielded similar SED and PA estimates along with relatively low measurement discords and did not have significant systematic biases for SED and Moderate-to-vigorous PA estimates. Our findings suggest that researchers may choose FF2 as a measurement of SED and PA when FF is not available in the market during the longitudinal PA research.

Keywords: sedentary behavior; physical activity; inter-device agreement; epidemiological (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2021
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