title: Validation of the Fitbit One® for physical activity measurement at an upper torso attachment site.
abstract: BACKGROUND
  The upper torso is recommended as an attachment site for the Fitbit One(®), one of the most common wireless physical activity trackers in the consumer market, and could represent a viable alternative to wrist- and hip-attachment sites. The objective of this study was to provide evidence concerning the validity of the Fitbit One(®) attached to the upper torso for measuring step counts and energy expenditure among female adults.
  
  
  RESULTS
  Thirteen female adults completed a four-phase treadmill exercise protocol (1.9, 3.0, 4.0, and 5.2 mph). Participants were fitted with three Fitbit(®) trackers (two Fitbit One(®) trackers: one on the upper torso, one on the hip; and a wrist-based Fitbit Flex(®)). Steps were assessed by manual counting of a video recording. Energy expenditure was measured by gas exchange indirect calorimetry. Concordance correlation coefficients of Fitbit-estimated step counts to observed step counts for the upper torso-attached Fitbit One(®), hip-attached Fitbit One(®) and wrist-attached Fitbit Flex(®) were 0.98 (95% CI 0.97-0.99), 0.99 (95% CI 0.99-0.99), and 0.75 (95% CI 0.70-0.79), respectively. The percent error for step count estimates from the upper torso attachment site was ≤3% for all walking and running speeds. Upper torso step count estimates showed similar accuracy relative to hip attachment of the Fitbit One(®) and were more accurate than the wrist-based Fitbit Flex(®). Similar results were obtained for energy expenditure estimates. Energy expenditure estimates for the upper torso attachment site yielded relative percent errors that ranged from 9 to 19% and were more accurate than the wrist-based Fitbit Flex(®), but less accurate than hip attachment of the Fitbit One(®).
  
  
  CONCLUSIONS
  Our study shows that physical activity measures obtained from the upper torso attachment site of the Fitbit One(®) are accurate across different walking and running speeds in female adults. The upper torso attachment site of the Fitbit One(®) outperformed the wrist-based Fitbit Flex(®) and yielded similar step count estimates to hip-attachment. These data support the upper torso as an alternative attachment site for the Fitbit One(®).
authors.affiliation: Center for Behavioral Cardiovascular Health, Department of Medicine, Columbia University Medical Center, 622 West 168th Street, PH 9-319, New York, NY, 10032, USA. kd2442@cumc.columbia.edu.
authors.forename: Keith M
authors.initials: KM
authors.lastname: Diaz
authors.affiliation: Center for Behavioral Cardiovascular Health, Department of Medicine, Columbia University Medical Center, 622 West 168th Street, PH 9-319, New York, NY, 10032, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Krupka
authors.affiliation: Center for Behavioral Cardiovascular Health, Department of Medicine, Columbia University Medical Center, 622 West 168th Street, PH 9-319, New York, NY, 10032, USA.
authors.forename: Melinda J
authors.initials: MJ
authors.lastname: Chang
authors.affiliation: Department of Psychology, University of Colorado Denver, Denver, CO, USA.
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Shaffer
authors.affiliation: Department of Biostatistics, Mailman School of Public Health, Columbia University, New York, NY, USA.
authors.forename: Yao
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Department of Biostatistics, Mailman School of Public Health, Columbia University, New York, NY, USA.
authors.forename: Jeff
authors.initials: J
authors.lastname: Goldsmith
authors.affiliation: Center for Behavioral Cardiovascular Health, Department of Medicine, Columbia University Medical Center, 622 West 168th Street, PH 9-319, New York, NY, 10032, USA.|Department of Psychiatry, Stony Brook University, New York, NY, USA.
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Schwartz
authors.affiliation: Center for Behavioral Cardiovascular Health, Department of Medicine, Columbia University Medical Center, 622 West 168th Street, PH 9-319, New York, NY, 10032, USA.
authors.forename: Karina W
authors.initials: KW
authors.lastname: Davidson
mesh_terms: D061725:Accelerometry / Q000295:instrumentation* / Q000379:methods; D000328:Adult; D002153:Calorimetry, Indirect; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise / Q000502:physiology; D005080:Exercise Test; D005260:Female; D006801:Humans; D008875:Middle Aged; D018670:Monitoring, Ambulatory / Q000295:instrumentation / Q000379:methods; D015203:Reproducibility of Results; D012420:Running / Q000502:physiology*; D060726:Torso / Q000502:physiology*; D016138:Walking / Q000502:physiology*; D055815:Young Adult
keywords: Accelerometer; Energy expenditure; Fitbit; Physical activity; Validation studies; Walking