Video-Recorded Validation of Wearable Step Counters under Free-living Conditions

AbstractPurposeThe purpose of this study was to determine the accuracy of 14 step counting methods under free-living conditions. MethodsTwelve adults (mean±SD, age: 35±13 yr) wore a chest harness that held a GoPro camera pointed down at the feet during all waking hours for one day. The GoPro continuously recorded video of all steps taken throughout the day. Simultaneously, participants wore two StepWatch [SW] devices on each ankle (all programmed with different settings), one activPAL [AP] on each thigh, four devices at the waist (Fitbit Zip [FZ], Yamax Digi-Walker SW-200 [DW], New Lifestyles NL-2000 [NL], and ActiGraph GT9X [AG]), and two devices on the dominant and non-dominant wrists (Fitbit Charge [FC] and AG). The GoPro videos were downloaded to a computer and researchers counted steps using a hand tally device, which served as the criterion method.ResultsThe SW devices recorded between 95.3% to 102.8% of actual steps taken throughout the day (P>0.05). Eleven step counting methods estimated less than 100% of actual steps; FZ, DW, and AG with the Moving Average Vector Magnitude algorithm (MAVM) on both wrists recorded 71% to 91% of steps (P>0.05), while the AP, NL, AG (without Low Frequency Extension [no-LFE], MAVM) worn on the hip, and FC recorded 69% to 84% of steps (P0.05), while the AG (LFE) on both wrists and the hip recorded 128% to 220% of steps (P0.05). Eleven step counting methods estimated less than 100% of actual steps; FZ, DW, and AG with the Moving Average Vector Magnitude algorithm (MAVM) on both wrists recorded 71% to 91% of steps (P>0.05), while the AP, NL, AG (without Low Frequency Extension [no-LFE], MAVM) worn on the hip, and FC recorded 69% to 84% of steps (P0.05), while the AG (LFE) on both wrists and the hip recorded 128% to 220% of steps (P

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