The Validity and Usability of Markerless Motion Capture and Inertial Measurement Units for Quantifying Dynamic...

Area of Science:

• Biomechanics
• Human movement analysis
• Motion capture technology

Background:

• Advancements in motion capture technology offer increased access to biomechanics data for researchers and clinicians.
• Markerless motion capture and inertial measurement units (IMUs) are emerging tools requiring validation for dynamic movements.
• Assessing the validity of new biomechanics tools is crucial before widespread adoption in applied settings.

Purpose of the Study:

• To evaluate the validity of markerless motion capture, IMUs, and RGBD camera systems.
• To compare these systems against marker-based motion capture during various dynamic movements.
• To determine the suitability of these technologies for capturing lower and upper body joint kinematics.

Main Methods:

• Thirty adult participants (18 female, 12 male) were recruited.
• Data were collected simultaneously using four systems: marker-based Vicon, markerless Theia/Optitrack, APDM Opals IMUs, and Vald HumanTrak RGBD camera.
• System validity was assessed using bias, RMSE, precision, maximum absolute error, and ICCs for joint angles.

Main Results:

• Markerless motion capture demonstrated the highest validity across sagittal, frontal, and transverse planes.
• IMU systems showed moderate validity, with higher RMSEs compared to markerless systems.
• The RGBD camera system exhibited inadequate validity, with significant bias observed in the sagittal and frontal planes.

Conclusions:

• Markerless motion capture and IMUs offer moderate validity for joint kinematics in dynamic movements.
• RGBD camera systems currently lack sufficient validity for reliable biomechanics analysis.
• System selection should consider specific movement tasks, testing environments, and available technical expertise.