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Validation of Inertial Measurement Units for Measuring Lower-Extremity Kinematics During Squat-Pivot and Stoop-Twist
Rutuja A Kulkarni1,2, Rajit Banerjee1,3, Vicki Z Wang1
1Human Engineering Research Laboratories, VA Pittsburgh Healthcare System, Pittsburgh, PA 15206, USA.
Sensors (Basel, Switzerland)
|September 27, 2025
Summary
Inertial measurement units (IMUs) show strong agreement with optokinetic motion capture (OMC) for measuring joint angles during lifting. IMUs offer a promising, portable alternative for field-based kinematic analysis of complex lifting tasks.
Area of Science:
- Biomechanics
- Human Movement Analysis
- Ergonomics
Background:
- Optokinetic motion capture (OMC) is the gold standard for lifting posture kinematics.
- OMC has limitations including cost, portability, and marker occlusion.
- Inertial measurement units (IMUs) offer a potential alternative for motion capture.
Purpose of the Study:
- To evaluate the agreement between OMC and IMUs for quantifying joint kinematics.
- To assess IMU accuracy during squat-pivot and stoop-twist lifting tasks.
Main Methods:
- Ten participants performed 24 lifting trials wearing both IMUs and OMC markers.
- Correlation coefficients and Root Mean Square Error (RMSE) were calculated for joint kinematics.
- Bland-Altman plots analyzed peak values between systems.
Main Results:
- High correlations (>0.9) observed for trunk, knee, and ankle flexion.
- Moderate correlations (0.5-0.7) for trunk axial rotation and lateral flexion.
- RMSE was consistently below 9°, with biases ranging from 0.3° to 16°.
Conclusions:
- IMUs demonstrate high agreement with OMC for key joint kinematics during lifting.
- IMUs are a viable tool for field data collection on complex lifting tasks.
- IMUs can accurately detect kinematic differences between lifting postures.
