{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,30]],"date-time":"2025-12-30T17:56:35Z","timestamp":1767117395199,"version":"build-2065373602"},"reference-count":53,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2022,1,13]],"date-time":"2022-01-13T00:00:00Z","timestamp":1642032000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003725","name":"National Research Foundation of Korea","doi-asserted-by":"publisher","award":["No. 2020R1A2C2102729"],"award-info":[{"award-number":["No. 2020R1A2C2102729"]}],"id":[{"id":"10.13039\/501100003725","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The present study was performed to investigate the validity of a wireless earbud-type inertial measurement unit (Ear-IMU) sensor used to estimate head angle during four workouts. In addition, relationships between head angle obtained from the Ear-IMU sensor and the angles of other joints determined with a 3D motion analysis system were investigated. The study population consisted of 20 active volunteers. The Ear-IMU sensor measured the head angle, while a 3D motion analysis system simultaneously measured the angles of the head, trunk, pelvis, hips, and knees during workouts. Comparison with the head angle measured using the 3D motion analysis system indicated that the validity of the Ear-IMU sensor was very strong or moderate in the sagittal and frontal planes. In addition, the trunk angle in the frontal plane showed a fair correlation with the head angle determined with the Ear-IMU sensor during a single-leg squat, reverse lunge, and standing hip abduction; the correlation was poor in the sagittal plane. Our results indicated that the Ear-IMU sensor can be used to directly estimate head motion and indirectly estimate trunk motion.<\/jats:p>","DOI":"10.3390\/s22020597","type":"journal-article","created":{"date-parts":[[2022,1,14]],"date-time":"2022-01-14T03:14:03Z","timestamp":1642130043000},"page":"597","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["The Validity of Wireless Earbud-Type Wearable Sensors for Head Angle Estimation and the Relationships of Head with Trunk, Pelvis, Hip, and Knee during Workouts"],"prefix":"10.3390","volume":"22","author":[{"given":"Ae-Ryeong","family":"Kim","sequence":"first","affiliation":[{"name":"Department of Rehabilitation Science, Jeonju University, Jeonju 55069, Korea"}]},{"given":"Ju-Hyun","family":"Park","sequence":"additional","affiliation":[{"name":"Department of Rehabilitation Science, Jeonju University, Jeonju 55069, Korea"}]},{"given":"Si-Hyun","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of Physical Therapy, Sangji University, Wonju 26339, Korea"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3672-5615","authenticated-orcid":false,"given":"Kwang Bok","family":"Kim","sequence":"additional","affiliation":[{"name":"Digital Health Care R&D Department, Korea Institute of Industrial Technology, Cheonan 31056, Korea"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3521-3121","authenticated-orcid":false,"given":"Kyue-Nam","family":"Park","sequence":"additional","affiliation":[{"name":"Department of Rehabilitation Science, Jeonju University, Jeonju 55069, Korea"},{"name":"Department of Physical Therapy, Jeonju University, Jeonju 55069, Korea"}]}],"member":"1968","published-online":{"date-parts":[[2022,1,13]]},"reference":[{"key":"ref_1","first-page":"109","article-title":"How did athletes train and avoid injuries during the covid-19 quarantine period?","volume":"28","author":"Husain","year":"2021","journal-title":"Trends Sport Sci."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Bereng\u00fc\u00ed, R., L\u00f3pez-Gull\u00f3n, J.M., and Angosto, S. 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