{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,17]],"date-time":"2026-07-17T04:04:41Z","timestamp":1784261081816,"version":"3.55.0"},"reference-count":33,"publisher":"MDPI AG","issue":"14","license":[{"start":{"date-parts":[[2026,7,16]],"date-time":"2026-07-16T00:00:00Z","timestamp":1784160000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000038","name":"Mercer On Mission-Prosthetic Program","doi-asserted-by":"publisher","award":["RGPIN-2018-04696"],"award-info":[{"award-number":["RGPIN-2018-04696"]}],"id":[{"id":"10.13039\/501100000038","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Background: Wearable inertial measurement units (IMoCAPs) are increasingly used in clinical gait analysis due to their portability and ability to capture data outside laboratory settings; however, validation across operating conditions is essential. Objective: To evaluate the concurrent validity and reliability of the Noraxon Ultium\u2122 IMU system against a Vicon optical motion capture (OMC) system for lower-limb kinematics during walking across different speeds and time intervals. Methods: Ten healthy adults performed overground walking at slow, normal, and fast self-selected speeds. Kinematics were recorded simultaneously using both systems. Discrete variables (Max, Min, ROM) were analyzed using three-factor repeated-measures ANOVA (Device \u00d7 Speed \u00d7 Time, p &lt; 0.05). Agreement was assessed using Bland\u2013Altman analysis, RMSE, and ICC (3,1), and waveform differences were evaluated using Statistical Parametric Mapping (SPM). Results: Time effects were minimal across all planes. Sagittal-plane kinematics showed strong agreement, with small biases (&lt;3\u00b0), low RMSE (\u22642.5\u00b0), and moderate reliability (ICC = 0.65\u20130.74). Both systems detected increased hip and knee motion with speed, although Device \u00d7 Speed interactions indicated greater IMoCAP underestimation at higher speeds. Frontal-plane agreement was poor to moderate (RMSE: 1\u20133\u00b0, ICC: 0.42\u20130.74). Transverse-plane kinematics demonstrated the largest discrepancies (RMSE up to 6\u20137\u00b0, ICC: 0.17\u20130.26), particularly for hip rotation. SPM revealed significant waveform differences across all planes. Conclusions: The Noraxon Ultium\u2122 IMU provides valid sagittal-plane gait assessment, moderate frontal-plane agreement, and limited reliability for transverse-plane kinematics, requiring cautious interpretation at higher speeds.<\/jats:p>","DOI":"10.3390\/s26144520","type":"journal-article","created":{"date-parts":[[2026,7,17]],"date-time":"2026-07-17T03:12:38Z","timestamp":1784257958000},"page":"4520","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Concurrent Validity and Reliability Between Noraxon Ultium\u2122 IMU and Vicon OMC for Lower Limb Gait Assessment Across Variable Walking Speeds"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0009-0005-7648-4632","authenticated-orcid":false,"given":"Trung T.","family":"Le","sequence":"first","affiliation":[{"name":"Department of Biomedical Engineering, School of Engineering, Mercer University, Macon, GA 31207, USA"},{"name":"Department of Interdisciplinary Engineering, College of Engineering, University of Guelph, Guelph, ON N1G 2W1, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ha V.","family":"Vo","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, School of Engineering, Mercer University, Macon, GA 31207, USA"},{"name":"Department of Orthopedic Surgery, School of Medicine, Mercer University, Macon, GA 31207, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1717-5889","authenticated-orcid":false,"given":"Scott C. E.","family":"Brandon","sequence":"additional","affiliation":[{"name":"Department of Interdisciplinary Engineering, College of Engineering, University of Guelph, Guelph, ON N1G 2W1, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,7,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"4","DOI":"10.1186\/1743-0003-3-4","article-title":"Gait analysis methods in rehabilitation","volume":"3","author":"Baker","year":"2006","journal-title":"J. Neuroeng. Rehabil."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.bspc.2007.09.001","article-title":"Human motion tracking for rehabilitation\u2014A survey","volume":"3","author":"Zhou","year":"2008","journal-title":"Biomed. Signal Process. 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