Background: Office workers experience neck or back pain due to poor posture, such as flexed head and forward head posture, during long-term sedentary work. Posture correction is used to reduce pain caused by poor posture and ensures proper alignment of the body. Several assistive devices have been developed to assist in maintaining an ideal posture; however, there are limitations in practical use due to vast size, unproven long-term effects or inconsistency of maintaining posture alignment. We developed a headphone and necklace posture correction system (HANPCS) for posture correction using an inertial measurement unit (IMU) sensor that provides visual or auditory feedback.
Objects: To demonstrate the test-retest reliability and concurrent validity of neck and upper trunk flexion measurements using a HANPCS, compared with a three-dimensional motion analysis system (3DMAS).
Methods: Twenty-nine participants were included in this study. The HANPCS was applied to each participant. The angle for each action was measured simultaneously using the HANPCS and 3DMAS. The data were analyzed using the intraclass correlation coefficient (ICC) = [3,3] with 95% confidence intervals (CIs).
Results: The angular measurements of the HANPCS for neck and upper trunk flexions showed high intra- (ICC = 0.954–0.971) and inter-day (ICC = 0.865–0.937) values, standard error of measurement (SEM) values (1.05°–2.04°), and minimal detectable change (MDC) values (2.92°–5.65°). Also, the angular measurements between the HANPCS and 3DMAS had excellent ICC values (> 0.90) for all sessions, which indicates high concurrent validity.
Conclusion: Our study demonstrates that the HANPCS is as accurate in measuring angle as the gold standard, 3DMAS. Therefore, the HANPCS is reliable and valid because of its angular measurement reliability and validity.

INTRODUCTION
MATERIALS AND METHODS
    1. Participants
    2. Instrumentation
    3. Procedures
    4. Statistical Analysis
RESULTS
DISCUSSION
CONCLUSIONS
FUNDING
ACKNOWLEDGEMENTS
CONFLICTS OF INTEREST
AUTHOR CONTRIBUTION
ORCID
REFERENCES

• Gyu-hyun Han(Department of Physical Therapy, The Graduate School, Yonsei University)
• Chung-hwi Yi(Department of Physical Therapy, College of Software and Digital Healthcare Convergence, Yonsei University, Wonju) Corresponding author
• Seo-hyun Kim(Department of Physical Therapy, The Graduate School, Yonsei University)
• Su-bin Kim(Department of Physical Therapy, The Graduate School, Yonsei University)
• One-bin Lim(epartment of Physical Therapy, Mokpo Science University, Mokpo, Korea)