title: When a Step Is Not a Step! Specificity Analysis of Five Physical Activity Monitors.
abstract: BACKGROUND
  Physical activity is an essential aspect of a healthy lifestyle for both physical and mental health states. As step count is one of the most utilized measures for quantifying physical activity it is important that activity-monitoring devices be both sensitive and specific in recording actual steps taken and disregard non-stepping body movements. The objective of this study was to assess the specificity of five activity monitors during a variety of prescribed non-stepping activities.
  
  
  METHODS
  Participants wore five activity monitors simultaneously for a variety of prescribed activities including deskwork, taking an elevator, taking a bus journey, automobile driving, washing and drying dishes; functional reaching task; indoor cycling; outdoor cycling; and indoor rowing. Each task was carried out for either a specific duration of time or over a specific distance. Activity monitors tested were the ActivPAL micro™, NL-2000™ pedometer, Withings Smart Activity Monitor Tracker (Pulse O2)™, Fitbit One™ and Jawbone UP™. Participants were video-recorded while carrying out the prescribed activities and the false positive step count registered on each activity monitor was obtained and compared to the video.
  
  
  RESULTS
  All activity monitors registered a significant number of false positive steps per minute during one or more of the prescribed activities. The Withings™ activity performed best, registering a significant number of false positive steps per minute during the outdoor cycling activity only (P = 0.025). The Jawbone™ registered a significant number of false positive steps during the functional reaching task and while washing and drying dishes, which involved arm and hand movement (P < 0.01 for both). The ActivPAL™ registered a significant number of false positive steps during the cycling exercises (P < 0.001 for both).
  
  
  CONCLUSIONS
  As a number of false positive steps were registered on the activity monitors during the non-stepping activities, the authors conclude that non-stepping physical activities can result in the false detection of steps. This can negatively affect the quantification of physical activity with regard to step count as an output. The Withings™ activity monitor performed best with regard to specificity during the activities of daily living tested.
authors.affiliation: Discipline of Physiology, School of Medicine, NUI Galway, Galway, Ireland.|Electrical & Electronic Engineering, School of Engineering & Informatics, NUI Galway, Galway, Ireland.
authors.forename: Sandra
authors.initials: S
authors.lastname: O'Connell
authors.affiliation: Electrical & Electronic Engineering, School of Engineering & Informatics, NUI Galway, Galway, Ireland.|National Centre for Biomedical Engineering Science, NUI Galway, Galway, Ireland.|CÚRAM - Centre for Research in Medical Devices, NUI Galway, Galway, Ireland.
authors.forename: Gearóid
authors.initials: G
authors.lastname: ÓLaighin
authors.affiliation: Discipline of Physiology, School of Medicine, NUI Galway, Galway, Ireland.|National Centre for Biomedical Engineering Science, NUI Galway, Galway, Ireland.|CÚRAM - Centre for Research in Medical Devices, NUI Galway, Galway, Ireland.
authors.forename: Leo R
authors.identifier: http://orcid.org/0000-0002-4011-6732
authors.initials: LR
authors.lastname: Quinlan
mesh_terms: D000328:Adult; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018670:Monitoring, Ambulatory / Q000295:instrumentation*; D009043:Motor Activity / Q000502:physiology*; D016138:Walking / Q000502:physiology*