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Open AccessArticle

On Placement, Location and Orientation of Wrist-Worn Tri-Axial Accelerometers during Free-Living Measurements

1
Department of Epidemiology and Biostatistics, School of Public Health-Bloomington, Indiana University, Bloomington, IN 47405, USA
2
Center for Aging and Population Health, Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15213, USA
*
Author to whom correspondence should be addressed.
Sensors 2019, 19(9), 2095; https://doi.org/10.3390/s19092095
Received: 12 March 2019 / Revised: 28 April 2019 / Accepted: 1 May 2019 / Published: 6 May 2019
(This article belongs to the Special Issue Inertial Sensors for Activity Recognition and Classification)
Wearable accelerometers have recently become a standalone tool for the objective assessment of physical activity (PA). In free-living studies, accelerometers are placed by protocol on a pre-defined body location (e.g., non-dominant wrist). However, the protocol is not always followed, e.g., the sensor can be moved between wrists or reattached in a different orientation. Such protocol violations often result in PA miscalculation. We propose an approach, PLOE (“Placement, Location and Orientation Evaluation method”), to determine the sensor position using statistical features from the raw accelerometer measurements. We compare the estimated position with the study protocol and identify discrepancies. We apply PLOE to the measurements collected from 45 older adults who wore ActiGraph GT3X+ accelerometers on the left and right wrist for seven days. We found that 15.6% of participants who wore accelerometers violated the protocol for one or more days. The sensors were worn on the wrong hand during 6.9% of the days of simultaneous wearing of devices. During the periods of discrepancies, the daily PA was miscalculated by more than 20%. Our findings show that correct placement of the device has a significant effect on the PA estimates. These results demonstrate a need for the evaluation of sensor position. View Full-Text
Keywords: wearable computing; sensor position; physical activity; ActiGraph GT3X+ wearable computing; sensor position; physical activity; ActiGraph GT3X+
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Straczkiewicz, M.; Glynn, N.W.; Harezlak, J. On Placement, Location and Orientation of Wrist-Worn Tri-Axial Accelerometers during Free-Living Measurements. Sensors 2019, 19, 2095.

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