Agreement Between Novice Visual Assessment and Classifications Derived from Markerless Motion Capture During...

Background: Visual assessment is commonly used in rehabilitation to evaluate movement quality during functional tasks such as sit-to-stand (STS) transfers. However, the extent to which observational ratings align with classifications derived from portable markerless motion capture systems remains unclear. This study examined agreement between novice observational ratings and motion-capture-derived classifications during STS performance. Methods: Fifty healthy adults performed STS transfers across three 18-inch seating conditions (firm, compliant, commode). Two final-year Doctor of Physical Therapy (DPT) students independently rated movement performance using a standardized observational rubric. Simultaneously, a portable markerless motion capture system (Kinotek) recorded joint kinematics, which were converted into ordinal severity classifications to enable a comparison. Inter-rater reliability and agreement were assessed using percent agreement and Krippendorff's alpha. Results: Exact agreement between novice raters was high across all surfaces (82.3-82.9%), while Krippendorff's alpha values were low despite high exact agreement (α = 0.250-0.323), consistent with restricted scale use. Agreement between observational ratings and motion-capture-derived classifications was low, with negative alpha values across all conditions (α = -0.224 to -0.561), indicating systematic differences in classification patterns. Observational raters more frequently assigned lower severity categories compared to motion-capture-derived classifications. Conclusions: Findings demonstrate low chance-corrected agreement under conditions of restricted scale use among novice raters and systematic disagreement between observational and motion-capture-derived classifications during STS performance. These findings reflect differences in classification approaches under the operational definitions used in this study. Motion capture was used as an objective comparator rather than a gold standard, and this study does not establish criterion validity. Further research is needed to evaluate agreement patterns in clinical populations and to examine how different measurement approaches influence functional movement classification.