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Movement Retraining using Real-time Feedback of Performance
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Repeatability and minimal detectable change including clothing effects for smartphone-based 3D markerless motion
Brian Horsak1, Hans Kainz2, Bernhard Dumphart1
1Center for Digital Health and Social Innovation, St. Pölten University of Applied Sciences, Campus-Platz 1, St. Pölten, 3100, Austria; Institute of Health Sciences, St. Pölten University of Applied Sciences, Campus-Platz 1, St. Pölten, 3100, Austria.
Journal of Biomechanics
|August 20, 2024
Summary
This study confirms OpenCap
Area of Science:
- Biomechanics
- Motion Capture Technology
Background:
- Markerless motion capture systems offer potential for wider accessibility.
- OpenCap, a smartphone-based system, requires evaluation for repeatability and influencing factors.
Purpose of the Study:
- To assess the intersession repeatability of OpenCap's gait and sit-to-stand kinematics.
- To investigate the impact of clothing on OpenCap measurements.
Main Methods:
- Test-retest study with 20 healthy volunteers.
- Evaluated walking and sit-to-stand tasks under minimal and regular clothing conditions.
- Utilized root-mean-square-deviation (RMSD), standard error of measurement (SEM), and minimal detectable change (MDC) for kinematic analysis.
Main Results:
- OpenCap demonstrated good intersession repeatability for gait and sit-to-stand kinematics (RMSD ~2.8-3.3 degrees).
- Highest variability observed in trunk, pelvis, and hip sagittal plane kinematics.
- Clothing had a minimal impact (<1 degree RMSD) on most kinematic variables.
Conclusions:
- OpenCap exhibits reliable performance for markerless motion capture, suitable for field studies.
- While generally reliable, some kinematic parameters require further technological improvement (MDC > 5 degrees).
- Consistent clothing is recommended to minimize variability in OpenCap measurements.
