Related Experiment Video
Updated: May 9, 2026
08:26
Comparative Analysis of Lower Limb Kinematics between the Initial and Terminal Phase of 5km Treadmill Running
Published on: July 17, 2020
Agreement and Repeatability of a Smartphone-Based Markerless System (OpenCap) Versus Marker-Based Motion Capture
Edilson Fernando de Borba1, Augusto Rossa Inda2, Bruna Machado Herberts2
1Department of Physical Education, Center for Studies in Motor Behavior, Federal University of Paraná, Curitiba, PR, Brazil.
Journal of Applied Biomechanics
|May 7, 2026
Summary
Smartphone-based markerless motion analysis (OpenCap) shows comparable validity and repeatability to traditional motion capture for treadmill walking and running. This technology could expand accessible 3D gait analysis.
Area of Science:
- Biomechanics
- Human movement analysis
- Wearable technology
Background:
- Marker-based motion capture is the gold standard for 3D gait analysis but is costly and lab-bound.
- Markerless smartphone tools like OpenCap offer potential for scalable gait assessment.
- The validity and repeatability of OpenCap for treadmill walking and running require investigation.
Purpose of the Study:
- To evaluate the agreement and repeatability of OpenCap compared to marker-based motion capture.
- To assess OpenCap's performance across different treadmill speeds (walking and running).
- To analyze spatiotemporal variables, joint angles, and center-of-mass displacement.
Main Methods:
- Simultaneous data collection using OpenCap and marker-based motion capture in 10 healthy adults.
- Gait analysis during treadmill walking (4 km/h) and running (8 and 14 km/h).
- Statistical analysis included Bland-Altman, ICCs, Pearson r, RMSE, and GaitSD for agreement and repeatability.
Main Results:
- Spatiotemporal metrics demonstrated minimal bias (near 0) and strong correlations (r ≥ .96) with OpenCap.
- Sagittal plane joint range of motion showed good-to-excellent reliability (ICCs = .76-.93).
- Waveform analysis revealed comparable repeatability between OpenCap and motion capture across speeds and variables.
Conclusions:
- OpenCap demonstrates comparable performance and repeatability to marker-based motion capture under controlled treadmill conditions.
- Smartphone-based markerless motion analysis is a viable tool for gait assessment.
- OpenCap has the potential to increase the accessibility of 3D gait analysis.
