Assessing agreement and usability of kinematic measures between markerless and marker-based motion capture systems...

Markerless motion capture technology can improve efficiency and accessibility in human biomechanics research, yet its accuracy and precision are not fully vetted. As markerless technology relies on the field-of-view from 2D video-based images from cameras, the effect of camera positioning on reliability of resulting kinematics and usability of such technology are not well understood. Various jumping tasks were concurrently recorded from 11 participants using three independent camera systems: two identical markerless camera systems positioned 1.4 and 3 m high, respectively, to assess precision between camera setups, and a marker-based system to assess accuracy relative to an industry standard. Usability of the markerless system was assessed using two novice and two experienced motion capture users. When assessing precision of kinematics, the markerless systems demonstrated a mean intraclass correlation coefficient of 0.95 ± 0.01 and mean root mean square error of 1.91 ± 0.98°. Relative to a marker-based system, the markerless system had a mean Lin's concordance correlation coefficient of 0.51 ± 0.19 and mean root mean square error of 3.29 ± 2.36°, after making bias-adjusting shifts in joint angles with the largest errors observed in hip flexion. Users rated the markerless system highly for ease and confidence of use. While differing definitions for the pelvis may systematically affect comparisons between marker-based and markerless systems, our data indicates that the evaluated markerless motion capture technology demonstrated good precision between identical systems using different camera perspectives, was accurate relative to a standard marker-based system, and was easy for novices and experienced users to acquire and process data.