# CREBAS: Computer-Based REBA Evaluation System for Wood Manufacturers Using MediaPipe
## 2 Backgrounds
### Musculoskeletal Risk Posture Analysis Technique  
The KOSHA suggests various precise evaluation methods to evaluate the harmful factors of musculoskeletal disorders of workers, and various studies are also being conducted for this purpose in many other countries. In the study [5], a statistical analysis on 1920 employees of 35 manufacturing companies through cluster sampling was conducted using questionnaires on demographic characteristics, ergonomics-related factors, occupational types, labor intensity, insomnia and Work-related Musculoskeletal Disorders (WMSD), determining the correlation with musculoskeletal disorders. In the study [6], musculoskeletal disorders were evaluated for workers of petrochemical companies. In this study, evaluation was also conducted through a questionnaire. For data analysis, Statistical Package for the Social Sciences (SPSS) was used to evaluate the risk of each job. However, for this evaluation method, the subjective opinion of the evaluator may hamper the ability to draw accurate results, and therefore an expert or systematic objective evaluation method is required. Precise evaluation of work posture is to determine the risk of musculoskeletal disorders by applying several evaluation techniques based on the posture of the worker, includingOWAS, RULA and REBA. The applied evaluation technique varies depending on the environment or method [7; 8; 9]. OWAS is a representative work posture evaluation technique developed by a steel company, Ovako Oy, in Finland in the mid-1970s, and then jointly modified by Ovako Oy and the Finish Institute for Occupational Health. OWAS is widely used because it is easy to learn and easy to apply in the field, but it is difficult to perform detailed analysis with because of the oversimplification of the working posture. The working posture is simply defined into four levels, and the results are also not specific, requiring additional detailed analysis procedures [8; 10]. RULA is a working posture assessment technique developed by [PERSON] and [PERSON] at the University of Nottingham, UK, in 1933. It was designed to quickly and easily evaluate the workload caused by working posture, by focusing on the upper limbs such as shoulders, wrists, and neck. RULA helps the use of the EU's minimum safety and health requirements for Visual Display Unit (VDU) workplaces and the UK's guidelines for occupational upper limb disorder prevention. RULA can quickly and easily determine the proportion of workers with upper limbs disorders caused by poor working posture, and it is possible to evaluate the muscle load caused by the task, by examining how working posture affects muscle fatigue, static or repetitive tasks and the force required for the task. Although RULA was developed for providing comprehensive ergonomic evaluation results, the focus is only on the upper limbs, limiting it in evaluating various working postures [8; 9; 10; 11; 12; 13]. The REBA assesses an individual worker's exposure to harmful factors associated with musculoskeletal disorders. Compared to RULA, which focuses on upper limbs, the range of the measurement is wide, so it is suitable for analyzing the degree of body burden and exposure to harmful factors in the automobile industry. It supplements the shortcomings of RULA, covering only the upper limbs, by evaluating wrists, forearms, elbows, shoulders, neck, trunk, waist, legs, knees, etc. [8; 9; 10; 12; 14]. Therefore, in order to evaluate the exact workload for the wood manufacturing industry studies in this paper, it is necessary to define the working posture and the appropriate evaluation method. Table 1 shows the characteristics and the reliability of each evaluation tool. RULA, which has been used in many previous studies, can evaluate the workload on the whole body, but it focuses on the workload on the arm. In the case of OWAS, the whole body is evaluated, but its oversimplification of posture prevent it from subdividing and evaluating various working postures.