When a step is not a step! Specificity analysis of five physical activity monitors

Abstract

IntroductionPhysical 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.MethodsParticipants 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 (TM), NL-2000 (TM) pedometer, Withings Smart Activity Monitor Tracker (Pulse O-2)(TM), Fitbit One (TM) and Jawbone UP (TM). 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.ResultsAll activity monitors registered a significant number of false positive steps per minute during one or more of the prescribed activities. The Withings (TM) activity performed best, registering a significant number of false positive steps per minute during the outdoor cycling activity only (P = 0.025). The Jawbone (TM) 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