title: Validation of Fitbit-Flex as a measure of free-living physical activity in a community-based phase III cardiac rehabilitation population.
abstract: Accurate physical activity monitoring is important for cardiac patients. Novel activity monitoring devices may enable precise measurement of physical activity. This study aimed to validate Fitbit-Flex against Actigraph accelerometer for monitoring physical activity.
  
  
  
  A validation study with a comparative design.
  
  
  
  Cardiac patients and family members participating in community-based exercise programs wore Fitbit-Flex and Actigraph simultaneously over four days to monitor daily step counts and minutes of moderate to vigorous physical activity (MVPA).
  
  
  
  Participants (N = 48) comprised 52.1% males, with a mean age of 65.6 ± 6.9 years and 58.9% had a cardiac diagnosis. Fitbit-Flex and Actigraph were significantly correlated in males, females, total participants and cardiac patients for step counts (r = .96; r = .95; r = .95; r = .95), though less so for MVPA (r = .81; r = .65, r = .74; r = .71). As step counts increased the differences between Fitbit-Flex and Actigraph also increased. Fitbit-Flex over-estimated step counts in females (556 steps/day), males (1462 steps/day) and total participants (1038 steps/day) as well as for minutes of MVPA in females (4 min/day), males (15 min/day) and total participants (10 min/day). Fitbit-Flex had high sensitivity and specificity in classifying participants who achieved the recommended physical activity guidelines.
  
  
  
  Fitbit-Flex is accurate in assessing attainment of physical activity guideline recommendations and is useful for monitoring physical activity in cardiac patients. The device does, however, slightly over-estimate step counts and MVPA.
authors.affiliation: Charles Perkins Centre, University of Sydney, Australia malh1196@uni.sydney.edu.au.
authors.forename: Muaddi
authors.initials: M
authors.lastname: Alharbi
authors.affiliation: Charles Perkins Centre, University of Sydney, Australia.
authors.forename: Adrian
authors.initials: A
authors.lastname: Bauman
authors.affiliation: Charles Perkins Centre, University of Sydney, Australia.
authors.forename: Lis
authors.initials: L
authors.lastname: Neubeck
authors.affiliation: Charles Perkins Centre, University of Sydney, Australia.
authors.forename: Robyn
authors.initials: R
authors.lastname: Gallagher
mesh_terms: D056044:Actigraphy / Q000295:instrumentation*; D000368:Aged; D000369:Aged, 80 and over; D000072038:Cardiac Rehabilitation; D004734:Energy Metabolism; D004867:Equipment Design; D015444:Exercise / Q000502:physiology*; D005260:Female; D006331:Heart Diseases / Q000503:physiopathology / Q000534:rehabilitation*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018670:Monitoring, Ambulatory / Q000295:instrumentation*; D015203:Reproducibility of Results; D016138:Walking
keywords: Actigraph; Coronary heart disease; Fitbit; accelerometer; activity monitor; cardiac rehabilitation; physical activity; validity