The Accuracy of a 2D Video-Based Lifting Monitor.

A widely used risk prediction tool, the revised NIOSH lifting equation (RNLE), provides the recommended weight limit (RWL), but is limited by analyst subjectivity, experience, and resources. This paper describes a robust, non-intrusive, straightforward approach to automatically extract spatial and temporal factors necessary for the RNLE using a single video camera in the sagittal plane. The participant's silhouette is segmented by motion information and the novel use of a ghosting effect provides accurate detection of lifting instances, and hand and feet location prediction. Laboratory tests using 6 participants, each performing 36 lifts, showed that a nominal 640pixel x 480pixel 2D video, in comparison to 3D motion capture, provided RWL estimations within 0.2kg (SD=1.0kg). The linear regression between the video and 3D tracking RWL was R-2 = 0.96 (slope = 1.0, intercept = 0.2kg). Since low definition video was used in order to synchronise with motion capture, better performance is anticipated using high definition video.Practitioner's summary: An algorithm for automatically calculating the revised NIOSH lifting equation using a single video camera was evaluated in comparison to laboratory 3D motion capture. The results indicate that this method has suitable accuracy for practical use and may be, particularly, useful when multiple lifts are evaluated.