Comparison of the Ovako Working Posture Analysis System, Rapid Upper Limb Assessment, and Rapid Entire Body Assessment based on the maximum holding times

Abstract

The objectives of this study were to measure the maximum holding times (MHTs) for symmetric and asymmetric body postures and to compare three representative observational methods, i.e., Ovako Working Posture Analysis System (OWAS), Rapid Upper Limb Assessment (RULA), and Rapid Entire Body Assessment (REBA), based on the MHTs. An experiment was performed to obtain the MHTs, wherein the independent variables were the hand position, trunk rotation angle, and external load. The hand position was defined using the hand height as the percentage of the shoulder height and the hand distance as the percentage of the arm reach. While the four independent variables including the hand height, hand distance, trunk rotation angle, and external load significantly affected the MHTs and RULA grand score at α = 0.01, only three of them (except the external load) were significant on the OWAS action category and REBA score. RULA assessed the postures tested in the experiment more stressfully than the OWAS and REBA, and the RULA grand score was more sensitive to the MHTs. In addition, the RULA grand score had larger correlation coefficients with the MHTs and other criteria for postural loads, such as whole-body discomfort, compressive force at L5/S1, and percent capables at the shoulder and trunk, than the OWAS action category and REBA score. Based on the findings of this study, it is concluded that of the three observational methods, RULA may be better for assessing postural loads under the experimental conditions. Relevance to industryWork-related musculoskeletal disorders are a major worldwide problem in industries. For preventing their development owing to multiple risk factors, it is important to quantify exposure to such risk factors.