{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,12]],"date-time":"2026-03-12T05:54:37Z","timestamp":1773294877600,"version":"3.50.1"},"reference-count":21,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2021,1,29]],"date-time":"2021-01-29T00:00:00Z","timestamp":1611878400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000925","name":"National Health and Medical Research Council","doi-asserted-by":"publisher","award":["2020-APP1180812"],"award-info":[{"award-number":["2020-APP1180812"]}],"id":[{"id":"10.13039\/501100000925","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Body postural allocation during daily life is important for health, and can be assessed with thigh-worn accelerometers. An algorithm based on sedentary bouts from the proprietary ActivePAL software can detect lying down from a single thigh-worn accelerometer using rotations of the thigh. However, it is not usable across brands of accelerometers. This algorithm has the potential to be refined. Aim: To refine and assess the validity of an algorithm to detect lying down from raw data of thigh-worn accelerometers. Axivity-AX3 accelerometers were placed on the thigh and upper back (reference) on adults in a development dataset (n = 50) and a validation dataset (n = 47) for 7 days. Sedentary time from the open Acti4-algorithm was used as input to the algorithm. In addition to the thigh-rotation criterion in the existing algorithm, two criteria based on standard deviation of acceleration and a time duration criterion of sedentary bouts were added. The mean difference (95% agreement-limits) between the total identified lying time\/day, between the refined algorithm and the reference was +2.9 (\u2212135,141) min in the development dataset and +6.5 (\u2212145,159) min in the validation dataset. The refined algorithm can be used to estimate lying time in studies using different accelerometer brands.<\/jats:p>","DOI":"10.3390\/s21030904","type":"journal-article","created":{"date-parts":[[2021,1,29]],"date-time":"2021-01-29T09:25:22Z","timestamp":1611912322000},"page":"904","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":33,"title":["Validity of a Non-Proprietary Algorithm for Identifying Lying Down Using Raw Data from Thigh-Worn Triaxial Accelerometers"],"prefix":"10.3390","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-1377-1923","authenticated-orcid":false,"given":"Pasan","family":"Hettiarachchi","sequence":"first","affiliation":[{"name":"Department of Medical Sciences, Occupational and Environmental Medicine, Uppsala University, 751 85 Uppsala, Sweden"}]},{"given":"Katarina","family":"Aili","sequence":"additional","affiliation":[{"name":"Spenshult Research and Development Center, 302 74 Halmstad, Sweden"},{"name":"School of Health and Welfare, Halmstad University, 301 18 Halmstad, Sweden"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4825-5697","authenticated-orcid":false,"given":"Andreas","family":"Holtermann","sequence":"additional","affiliation":[{"name":"National Research Centre for the Working Environment, 2100 Copenhagen, Denmark"},{"name":"Department of Sport Science and Clinical Biomechanics, University of Southern Denmark, 5230 Odense, Denmark"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7323-3225","authenticated-orcid":false,"given":"Emmanuel","family":"Stamatakis","sequence":"additional","affiliation":[{"name":"Charles Perkins Centre, School of Health Sciences, Faculty of Medicine and Health, University of Sydney, Sydney, NSW 2006, Australia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8165-7236","authenticated-orcid":false,"given":"Magnus","family":"Svartengren","sequence":"additional","affiliation":[{"name":"Department of Medical Sciences, Occupational and Environmental Medicine, Uppsala University, 751 85 Uppsala, Sweden"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9354-6704","authenticated-orcid":false,"given":"Peter","family":"Palm","sequence":"additional","affiliation":[{"name":"Department of Medical Sciences, Occupational and Environmental Medicine, Uppsala University, 751 85 Uppsala, Sweden"}]}],"member":"1968","published-online":{"date-parts":[[2021,1,29]]},"reference":[{"key":"ref_1","unstructured":"World Health Organization (2020, December 14). WHO Guidelines on Physical Activity and Sedentary Behaviour. Available online: https:\/\/apps.who.int\/iris\/handle\/10665\/336656."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"l4570","DOI":"10.1136\/bmj.l4570","article-title":"Dose-response associations between accelerometry measured physical activity and sedentary time and all cause mortality: Systematic review and harmonised meta-analysis","volume":"366","author":"Ekelund","year":"2019","journal-title":"BMJ"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"137","DOI":"10.1111\/joim.12908","article-title":"Measurement of physical activity in clinical practice using accelerometers","volume":"286","author":"Arvidsson","year":"2019","journal-title":"J. Intern. Med."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"76","DOI":"10.1123\/jpah.2011-0347","article-title":"Detection of Physical Activity Types Using Triaxial Accelerometers","volume":"11","author":"Skotte","year":"2014","journal-title":"J. Phys. Act. Health"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"435","DOI":"10.1136\/bjsports-2019-100786","article-title":"Emerging collaborative research platforms for the next generation of physical activity, sleep and exercise medicine guidelines: The Prospective Physical Activity, Sitting, and Sleep consortium (ProPASS)","volume":"54","author":"Stamatakis","year":"2019","journal-title":"Br. J. Sports Med."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"e000874","DOI":"10.1136\/bmjsem-2020-000874","article-title":"Thigh-worn accelerometry for measuring movement and posture across the 24-hour cycle: A scoping review and expert statement","volume":"6","author":"Stevens","year":"2020","journal-title":"BMJ Open Sport Exerc. Med."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"162","DOI":"10.1016\/j.jshs.2016.02.002","article-title":"Considerations when using the activPAL monitor in field-based research with adult populations","volume":"6","author":"Edwardson","year":"2017","journal-title":"J. Sport Health Sci."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"2025","DOI":"10.1249\/MSS.0000000000000326","article-title":"Detection of Lying Down, Sitting, Standing, and Stepping Using Two ActivPAL Monitors","volume":"46","author":"Bassett","year":"2014","journal-title":"Med. Sci. Sports Exerc."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"233","DOI":"10.1177\/0269215517724850","article-title":"Validity and reliability of accelerometry in identification of lying, sitting, standing or purposeful activity in adult hospital inpatients recovering from acute or critical illness: A systematic review","volume":"32","author":"Anderson","year":"2018","journal-title":"Clin. Rehabil."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"742","DOI":"10.1249\/MSS.0000000000000804","article-title":"Differentiating Sitting and Lying Using a Thigh-Worn Accelerometer","volume":"48","author":"Lyden","year":"2016","journal-title":"Med. Sci. Sports Exerc."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1888","DOI":"10.1111\/sms.13203","article-title":"Comparison of single- and dual-monitor approaches to differentiate sitting from lying in free-living conditions","volume":"28","author":"Smits","year":"2018","journal-title":"Scand. J. Med. Sci. Sports"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"88","DOI":"10.2519\/jospt.1998.28.2.88","article-title":"Knee Injury and Osteoarthritis Outcome Score (KOOS)\u2014Development of a Self-Administered Outcome Measure","volume":"28","author":"Roos","year":"1998","journal-title":"J. Orthop. Sports Phys. Ther."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"439","DOI":"10.1111\/j.1600-0838.1998.tb00465.x","article-title":"Knee injury and Osteoarthritis Outcome Score (KOOS)\u2014Validation of a Swedish version","volume":"8","author":"Roos","year":"2007","journal-title":"Scand. J. Med. Sci. Sports"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"738","DOI":"10.1152\/japplphysiol.00421.2014","article-title":"Autocalibration of accelerometer data for free-living physical activity assessment using local gravity and temperature: An evaluation on four continents","volume":"117","author":"Fang","year":"2014","journal-title":"J. Appl. Physiol."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"953","DOI":"10.1080\/00140139.2014.998724","article-title":"Validity of the Acti4 method for detection of physical activity types in free-living settings: Comparison with video analysis","volume":"58","author":"Stemland","year":"2015","journal-title":"Ergonomics"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1186\/s12966-019-0835-0","article-title":"Comparison of physical behavior estimates from three different thigh-worn accelerometers brands: A proof-of-concept for the Prospective Physical Activity, Sitting, and Sleep consortium (ProPASS)","volume":"16","author":"Crowley","year":"2019","journal-title":"Int. J. Behav. Nutr. Phys. Act."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"135","DOI":"10.1177\/096228029900800204","article-title":"Measuring agreement in method comparison studies","volume":"8","author":"Bland","year":"1999","journal-title":"Stat. Methods Med Res."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"992","DOI":"10.1136\/bjsm.2006.030262","article-title":"The validation of a novel activity monitor in the measurement of posture and motion during everyday activities","volume":"40","author":"Grant","year":"2006","journal-title":"Br. J. Sports Med."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"42","DOI":"10.1016\/j.gaitpost.2015.10.020","article-title":"Validity and reliability of the activPAL3 for measuring posture and stepping in adults and young people","volume":"43","author":"Sellers","year":"2016","journal-title":"Gait Posture"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1653","DOI":"10.1088\/0967-3334\/37\/10\/1653","article-title":"Identifying adults\u2019 valid waking wear time by automated estimation in activPAL data collected with a 24 h wear protocol","volume":"37","author":"Winkler","year":"2016","journal-title":"Physiol. Meas."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1867","DOI":"10.1080\/02640414.2016.1140908","article-title":"Identifying waking time in 24-h accelerometry data in adults using an automated algorithm","volume":"34","author":"Willems","year":"2016","journal-title":"J. Sports Sci."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/3\/904\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T05:17:04Z","timestamp":1760159824000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/3\/904"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,1,29]]},"references-count":21,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2021,2]]}},"alternative-id":["s21030904"],"URL":"https:\/\/doi.org\/10.3390\/s21030904","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,1,29]]}}}