# Towards an Ergonomic Assessment Framework for Industrial Assembly Workstations--A Case Study
## 2 Materials and Methods
### Preassembly Workstation--Ergonomic Assessment  
As mentioned above, the new workstation (the preassembly workstation) was designed to accommodate the workers with musculoskeletal complaints. A group of 8 workers was selected and reallocated to this workstation. The analysis of this redesign began with the quantification of task times associated with the preassembly process. These times will provide a future reference to measure COBOT workstation efficiency. To uphold a rigorous and precise standard, various cycles of the preassembly process were recorded in video format as part of a time-motion study. The process was initially segmented into a set of well-defined tasks coordinated by the two operators in the work cell. With the intent of collecting demographic and psychophysical assessments, a questionnaire was also applied to the preassembly workers as well. In this case, the questionnaire was adapted to compare tasks and workstations and thus it has four categories, see Table 2. \begin{table}
\begin{tabular}{p{42.7 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline  & **Questions’ Category** & **Parameters Assessed** & **Objectives** & **Tools Applied** \\ \hline A. & Workers’ characterization & Gender, age, work experience, preferred hand; WMSD. & To characterize the workers’ sample with demographic data. & Direct questions. \\ B. & Assessment of Musculoskeletal symptoms & Musculoskeletal for the entire body. & To characterize musculoskeletal symptoms of the preassembly workers. & NMQ with closed answers ”yes/no” and \\ C. & Assessment of risk factors & 14 topics that influence the ergonomic conditions. & To assess globally the workstation by the workers’ perceptions. & VAS to assess pain intensity. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of the questionnaire’s structure—assembly workers. The first part of this questionnaire has the same categories as the previous one, related to the workers' characterization and assessment of musculoskeletal symptoms. The questionnaire category C related to the self-reported physical exertion at the new workstation was evaluated using the \"Category Ratio-10\" (CR-10) [29]. [PERSON] [29] argues that the application of scales similar to CR-10 is necessary to quantify and dismiss subjective sensations of physical overload, such as the perception of effort and discomfort. An advantage of the CR-10 scale is that each score is associated with an effort that is perceived by different individuals. This puts in perspective the physical effort perceived by different workers and/or the effect of different work conditions. The last category (D category) was composed of six statements related to the changes introduced at the assembly activity. The workers have to classify the statement using a 5-Likert scale. Workers are requested to indicate their level of agreement with each particular statement. The 5-Likert scale is labeled as follows: 1 = Strongly disagree; 2 = Disagree; 3 = Neutral; 4 = Agree; 5 = Strongly agree. Additionally, considering the ergonomic challenge associated with this case study, the ergonomic assessment included the application of methods more specific for the work tasks understudy. This more focused assessment allows the definition of ergonomic requirements to improve this workstation. Therefore, considering observation of different work cycles, a total of 38 postures were assessed by the following methods: RULA [14] and KIM-MHO [29]. For the postures selection, the following criteria were applied: (i) representativeness considering the postures more frequent; (ii) selection of the hand (right or left) according to the higher exertion involved; (iii) for tasks with more complex manual work, both hands were separately assessed. The tasks studied were cyclic and exposed workers to a variety of upper extremity activities of varying force, postures and repetitive motion. The task cycle times were measured during the time-motion study.