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Variations in Concurrent Validity of Two Independent Inertial Measurement Units Compared to Gold Standard for Upper
Roger Lee1,2, Riad Akhundov1,3,4, Carole James5
1School of Health Sciences, College of Health, Medicine and Wellbeing, The University of Newcastle, Callaghan, NSW 2308, Australia.
Sensors (Basel, Switzerland)
|August 12, 2023
Summary
Wi-Fi inertial measurement units (IMUs) show good accuracy for measuring upper body posture during computer use compared to motion capture. Bluetooth IMUs had moderate accuracy, with both systems affected by drift.
Area of Science:
- Biomechanics
- Human-Computer Interaction
- Wearable Technology
Background:
- Inertial measurement units (IMUs) offer a potential objective method for assessing posture during computer use.
- Validation studies are crucial to determine the accuracy of IMUs for posture measurement outside laboratory settings.
Purpose of the Study:
- To examine the concurrent validity of two IMU systems (Wi-Fi and Bluetooth) against a 3D motion capture system (Mocap).
- To assess the accuracy of IMUs in measuring three-dimensional upper body posture during various computer tasks.
Main Methods:
- Twenty-six participants performed computer tasks with different monitor setups (correct, raised, laptop).
- 3D Mocap and two IMU systems (Wi-Fi, Bluetooth) captured upper body posture data.
- Coefficient of determination (R² ) and root-mean-square error (RMSE) were used for comparison.
Main Results:
- Wi-Fi IMUs demonstrated high validity for head/neck (HN) and upper trunk segment (UTS) in the sagittal plane, and HN-UTS in the frontal plane.
- Wi-Fi IMUs showed moderate to poor validity for other movements, including trunk rotations.
- Bluetooth IMUs exhibited moderate validity for HN and UTS in the sagittal plane across conditions, but poor validity for frontal plane and rotation movements.
- Both systems experienced gyroscopic drift; Bluetooth IMUs also had data loss.
Conclusions:
- Wi-Fi IMUs provide more acceptable accuracy for upper body posture measurement during computer use compared to Mocap, excluding trunk rotations.
- The performance variation between IMU systems highlights the necessity of task-specific validation for accurate posture assessment.
