Reliability and validity of a 2-D video digitizing system during a static and a dynamic task

Context: The SMART (TM) software system offers low-cost kinematic analysis through digitization of video from a single camera. The reliability and validity of this product have not been reported. Objective: To assess the reliability and validity of the SMART software during a simple static task and dynamic task. Design: Test-retest to compare assumed neutral and goniometrically measured joint angles in the sagittal plane of the lower extremity. Setting: Research laboratory. Participants: 7 in a static task, 16 young, physically active in a dynamic task. Results: Measurement error of the SMART system ranged from 0.29 degrees +/- 1.98 degrees to 11.07 degrees +/- 1.77 degrees. The interrater reliability (ICC2,1) values ranged from .60 to .92 for the static task and from .76 to .89 for the dynamic task. Conclusions: Based on the results of both studies, the SMART system offers a low-cost alternative for reporting single-plane kinematics during an individual frame of video during static stances and slow dynamic tasks with strong reliability and reasonable validity.