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Concurrent validity of the Fitbit for assessing sedentary behavior and moderate-to-vigorous physical activity
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Concurrent validity of the Fitbit for assessing sedentary behavior and moderate-to-vigorous physical activity
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Concurrent validity of the Fitbit for assessing sedentary behavior and moderate-to-vigorous physical activity
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Journal Article
Concurrent validity of the Fitbit for assessing sedentary behavior and moderate-to-vigorous physical activity
2019
Overview
Background
Recent advances in sensor technologies have promoted the use of consumer-based accelerometers such as Fitbit Flex in epidemiological and clinical research; however, the validity of the Fitbit Flex in measuring sedentary behavior (SED) and physical activity (PA) has not been fully determined against previously validated research-grade accelerometers such as ActiGraph GT3X+. Therefore, the purpose of this study was to examine the concurrent validity of the Fitbit Flex against ActiGraph GT3X+ in a free-living condition.
Methods
A total of 65 participants (age: M = 42, SD = 14 years, female: 72%) each wore a Fitbit Flex and GT3X+ for seven consecutive days. After excluding sleep and non-wear time, time spent (min/day) in SED and moderate-to-vigorous PA (MVPA) were estimated using various cut-points for GT3X+ and brand-specific algorithms for Fitbit, respectively. Repeated measures one-way ANOVA and mean absolute percent errors (MAPE) served to examine differences and measurement errors in SED and MVPA estimates between Fitbit Flex and GT3X+, respectively. Pearson and Spearman correlations and Bland-Altman (BA) plots were used to evaluate the association and potential systematic bias between Fitbit Flex and GT3X+. PROC MIXED procedure in SAS was used to examine the equivalence (i.e., the 90% confidence interval with ±10% equivalence zone) between the devices.
Results
Fitbit Flex produced similar SED and low MAPE (mean difference [MD] = 37 min/day,
P
= .21, MAPE = 6.8%), but significantly higher MVPA and relatively large MAPE (MD = 59–77 min/day,
P
< .0001, MAPE = 56.6–74.3%) compared with the estimates from GT3X+ using three different cut-points. The correlations between Fitbit Flex and GT3X+ were consistently higher for SED (r = 0.90, ρ = 0.86,
P
< .01), but weaker for MVPA (r = 0.65–0.76, ρ = 0.69–0.79,
P
< .01). BA plots revealed that there is no apparent bias in estimating SED.
Conclusion
In comparison with the GT3X+ accelerometer, the Fitbit Flex provided comparatively accurate estimates of SED, but the Fitbit Flex overestimated MVPA under free-living conditions. Future investigations using the Fitbit Flex should be aware of present findings.
Publisher
BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
Subject
/ Accelerometry - instrumentation
/ Accelerometry - statistics & numerical data
/ Adult
/ Exercise
/ Female
/ Humans
/ Male
/ Medicine
/ Monitoring, Ambulatory - instrumentation
/ Monitoring, Ambulatory - methods
/ Monitoring, Ambulatory - statistics & numerical data
/ Sensors
/ Statistical Theory and Methods
/ Statistics for Life Sciences
/ Theory of Medicine/Bioethics
/ Validity
/ Walking
