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Updated: Apr 13, 2026
Sit-to-stand-and-walk from 120% Knee Height: A Novel Approach to Assess Dynamic Postural Control Independent of Lead-limb
Published on: August 30, 2016
Concurrent validity of Theia3D markerless compared to marker-based motion capture for movement synergy analysis
Arunee Promsri1, Anna Wargel2, Peter Federolf2
1Department of Physical Therapy, School of Allied Health Sciences, University of Phayao, Phayao 56000, Thailand.
Abstract:
Markerless motion capture systems offer a feasible alternative to laboratory-based, marker-based setups, yet their validity for synergy-based analysis during dynamic clinical tasks remains insufficiently understood. This study evaluated the concurrent validity of Theia3D against Vicon marker-based motion capture for analyzing movement synergies during the 1-Minute Sit-to-Stand test (1MSTS) performed under eyes-open (EO) and eyes-closed (EC) conditions. Thirteen healthy adults completed randomized EO and EC 1MSTS trials recorded simultaneously by Theia3D and Vicon at 200 Hz. Whole-body kinematics were analyzed using principal component analysis to extract principal movements (PMs), representing coordination patterns. Waveform similarity between systems for principal positions, velocities, and accelerations (PP1-10, PV1-10, PA1-10) was quantified using Pearson correlations (r). Relative variance contributions (PPk_rVAR) were compared to assess visual condition effects. Both systems produced highly similar dominant PMs. PM1-3, representing rising, trunk flexion, and backward hip translation, showed strong to excellent cross-system correlations (r = 0.84-0.99). Agreement decreased for higher-order PMs, although several synergies appeared in different PM ranks due to mode reordering. Theia3D and Vicon both detected EO-EC effects, though redistributed variance emerged in different PMs depending on system-specific sensitivity to mid- or high-order synergies. These findings demonstrate that Theia3D validly reproduces the major 1MSTS coordination patterns captured by Vicon and is sensitive to sensory-driven adaptations. While agreement for higher-order components was lower, the dominant synergies-accounting for more than 98% of total variance-showed excellent consistency. Theia3D appears suitable for clinical and applied environments requiring efficient, markerless assessment of functional movement strategies.
