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Physical Activity Among Children – Objective Measurements Using Fitbit One® and ActiGraph

Lotta Hamari, Tiina Kullberg, Jukka Ruohonen, Olli J. Heinonen, Natalia Díaz Rodríguez, Johan Lilius, Anni Pakarinen, Annukka Myllymäki, Ville Leppänen, Sanna Salanterä, Physical Activity Among Children – Objective Measurements Using Fitbit One® and ActiGraph. BMC Research Notes 10, 1–6, 2017.


Background: Self-quantification of health parameters is becoming more popular; thus, the validity of the devices requires assessments. The aim of this study was to evaluate the validity of Fitbit One step counts (Fitbit Inc., San Francisco, CA, USA) against Actigraph wActisleep-BT step counts (ActiGraph, LLC, Pensacola, FL, USA) for measuring habitual physical activity among children.

Design: The study was implemented as a cross-sectional experimental design in which participants carried two waist-worn activity monitors for five consecutive days.
Methods: The participants were chosen with a purposive sampling from three fourth grade classes (9–10 year olds) in two comprehensive schools. Altogether, there were 34 participants in the study. From these, eight participants were excluded from the analysis due to erroneous data. Primary outcome measures for step counts were Fitbit One and Actigraph wActisleep-BT. The supporting outcome measures were based on activity diaries and initial information sheets. Classical Bland-Altman plots were used for reporting the results.

Results: The average per-participant daily difference between the step counts from the two devices was 1 937. The range was [116, 5 052]. Fitbit One gave higher step counts for all but the least active participant. According to a Bland-Altman plot, the hourly step counts had a relative large mean bias across participants (161 step counts). The differences were partially explained by activity intensity: higher intensity denoted higher differences, and light intensity denoted lower differences.

Conclusions: Fitbit One step counts are comparable to Actigraph step counts in a sample of 9–10-year-old children engaged in habitual physical activity in sedentary and light physical activity intensities. However, in moderate-to-vigorous physical activity, Fitbit One gives higher step counts when compared to Actigraph.


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BibTeX entry:

  title = {Physical Activity Among Children – Objective Measurements Using Fitbit One® and ActiGraph},
  author = {Hamari, Lotta and Kullberg, Tiina and Ruohonen, Jukka and Heinonen, Olli J. and Díaz Rodríguez, Natalia and Lilius, Johan and Pakarinen, Anni and Myllymäki, Annukka and Leppänen, Ville and Salanterä, Sanna},
  journal = {BMC Research Notes},
  volume = {10},
  publisher = {BioMed Central},
  pages = {1–6},
  year = {2017},
  keywords = {Accelerometer, Physical activity, Motor activity, Movement, Children, Investigative techniques},
  ISSN = {1756-0500},

Belongs to TUCS Research Unit(s): Turku BioNLP Group, Embedded Systems Laboratory (ESLAB)

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