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
Open accessAbstract
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.
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In variables like head angle or knee in the frontal plane, IMUs represent a more robust alternative, as they provide high-frequency, three-dimensional orientation data that is independent of camera position and field of view.
“In variables like head angle or knee in the frontal plane IMUs represent a more robust alternative [60,61,62], as they provide high-frequency, three-dimensional orientation data that is independent of camera position and field of view.”
From Intra-Rater and Test–Retest Reliability of Kinovea for the Kinematic Analysis of Squatting in Healthy Active Women (2026) · cites this paper as [62]
The Discussion and Conclusions report moderate-to-very-strong validity for earbud-IMU head-angle measurements in the sagittal and frontal planes during workouts. The Instruments section reports 100 Hz sampling, but the Data Processing section says the study estimated only sagittal and frontal angles; knee angles were measured by the 3D motion-analysis system, not the IMU. The paper does not establish a robustness advantage based on camera position or field of view. (LLM, conf=0.88)
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- Authors
- Kim, A.-R., Park, J.-H., Kim, S.-H., Kim, K. B., & Park, K.-N.
- Affiliations
- Jeonju University (KR)
- Sangji University (KR)
- Korea Institute of Industrial Technology (KR)
- Department of Rehabilitation Science, Jeonju University, Jeonju 55069, Korea
- Venue
- Sensors
- Publisher
- MDPI AG
- Published
- 2022-01-13
- Volume
- 22
- Issue
- 2
- Pages
- 597
- ISSN
- 1424-8220 (ISSN-L)
- PMC
- PMC8780408
- OpenAlex
- W4205838152
- Cited by
- 12
- References
- 51
- Citations by year
- 2026: 4 · 2025: 2 · 2024: 3 · 2023: 1 · 2022: 2
- FWCI
- 0.65
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Licence
- Locations
- Sensors (publishedVersion, cc-by)
- PubMed Central (publishedVersion, cc-by)
- PubMed (publishedVersion)
- DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
- Funders
- National Research Foundation of Korea (No. 2020R1A2C2102729)
- Topics
- Physical Sciences › Computer Science › Computer Vision and Pattern Recognition › Context-Aware Activity Recognition Systems
- Physical Sciences › Engineering › Aerospace Engineering › Inertial Sensor and Navigation
- Physical Sciences › Engineering › Biomedical Engineering › Sports Dynamics and Biomechanics
- Keywords
- inertial measurement unit, wearable sensors, sensor validity, 3D motion analysis, trunk angle, hip joint angle, knee joint angle, pelvic angle, single-leg squat
- MeSH terms
- Wearable Electronic Devices, Biomechanical Phenomena, Humans, Knee Joint, Pelvis, Torso
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