Background: The term physical behavior includes sedentary and non-sedentary everyday physical activities. Objective measurement methods are recommended when sedentary behaviors are to be measured. Data from a thigh worn accelerometer can, together with the Acti4 software, be used to distinguish different physical behaviors. Due to different shapes of thighs and how the accelerometers have been placed on the thighs there is a need to compensate for individual differences in reference angles in respect to gravity. Normally this is done by letting the participants perform a reference position when they stand up and that time is noted in a diary. However, this is very time consuming. One alternative is to automatically estimate the compensation angles from walking episodes in the existing data. Objective: The aim of this study was to validate two new features to the Acti4 software, detection of lying and automatic reference angle generation. Methods: Ten participants underwent a 45-minute standardized protocol, and a 48-hour free-living protocol, with recordings of the different physical behaviors lying, sitting, standing, walking, running, stair walking, and cycling. Video recordings of the standardized protocol, and accelerometer data and diaries together with the participants review of the results from the software from the free-living protocol, has been used to validate the software. Results: During the standardized protocol, the overall accumulated performance of the software to identify the same physical behavior as in the video recordings was 81.1% (sensitivity), 96.7% (specificity) and 94.8% (accuracy). Participants agreed that most identified physical behavior episodes were correct, when reviewing the result from the software. When the two different reference angle generation methods were compared, almost no difference was found in the results of the standardized protocol, neither when comparing total time registered per behavior accumulated for all participants during the free-living protocol. Conclusions: The software may be used in research as a valid tool to measure physical behavior. However, the sensitivity to detect lying and stair walking may vary between individuals. When conducting research with thigh worn accelerometers, researchers may use the easier to use method with automatically generated reference angles instead of the more burdensome method with manually recorded diary annotation.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:kth-287457 |
| Date | January 2020 |
| Creators | Höjvall, Christofer |
| Publisher | KTH, Ergonomi |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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