Risk factors for the assessment of musculoskeletal disorders in tree-felling operations using the Rapid Upper Limb Assessment (RULA) method

Background and Objectives: Although considerable technological and organizational progress has been made in the forest sector over recent decades, the practical contribution of ergonomics to improving the working conditions of forest workers remains limited. Most existing studies have primarily emphasized productivity enhancement, cost reduction, equipment efficiency, and workflow optimization, while comparatively little attention has been given to human-centered challenges such as worker comfort, musculoskeletal health, occupational fatigue, long-term well-being, and injury prevention. Given these concerns, this study aimed to systematically analyze the working postures of chainsaw operators using the Rapid Upper Limb Assessment (RULA) method and to determine the level of ergonomic risk across different stages of the tree-felling process. Additionally, the study sought to identify necessary ergonomic interventions that could effectively reduce posture-related risks and improve overall occupational safety.
Methodology: The analysis of risk factors associated with tree felling was performed by observing working postures using the Rapid Upper Limb Assessment (RULA) method during felling operations. The RULA method is an ergonomic analysis tool used to assess potentially harmful physical working postures. In this study, the clear-cutting of poplar trees in Parcel 14, Series 2, Gisum, western Guilan Province, was investigated. A total of 430 photographs of working postures related to the assessment components, including movement between trees, undercutting, backcutting, and the posture of the felling operator, were recorded and evaluated. Scoring of working postures for different body regions was performed in two categories: Group A (arm, forearm, and wrist) and Group B (trunk, neck, and legs). Based on the scores obtained for each examined posture, four action levels were determined: action level one (acceptable), action level two (further investigation and changes may be needed), action level three (changes are required as soon as possible), and action level four (changes are required immediately).
Results: The findings revealed distinct posture patterns across different stages of felling. In the arm posture category, the most frequently observed code during tree evaluation (48.1%), undercutting (47.2%), and movement between trees (66.7%) was code 1, while backcutting postures more often fell under code 4 (27.9%), indicating higher strain. Forearm postures were primarily coded as 2 during evaluation and as 1 during the undercutting, backcutting, and movement stages. Wrist posture analysis showed that code 2 was dominant across all stages. Wrist rotation postures also frequently fell under higher-risk codes, particularly code 2, which occurred in 89.9% of evaluation, 94.9% of undercutting, 98.4% of backcutting, and 66.7% of movement observations. Neck posture results indicated that code 1 was most common during tree evaluation (49.4%), whereas code 2 was more frequent during undercutting (34.6%), backcutting (50.8%), and movement (40%). Trunk posture was notably problematic; during tree evaluation, code 4—representing a high trunk load—accounted for 65.8% of observations. In contrast, during the undercutting, backcutting, and movement stages, code 1 was most frequent (50%, 37.7%, and 53.3%, respectively). Leg posture was consistently categorized under code 1 across all stages. Final RULA action levels revealed significant differences among tasks, with the highest frequencies occurring at levels 2 and 3, indicating a clear need for corrective actions. The undercutting and backcutting stages showed the greatest proportion of high-risk postures.
Conclusion: The study demonstrates that chainsaw operators are routinely exposed to biomechanically demanding postures that place them at significant risk of developing musculoskeletal disorders. The RULA assessment provides evidence that ergonomic interventions, such as training in safe postural techniques, redesign of tools or workflow, and improved task organization, are needed. Enhancing workers’ awareness of correct posture and integrating ergonomic principles into forest operations can substantially reduce risk levels, improve safety, and contribute to sustainable workforce health.