Comparison of six observational methods for repetitive shoulder movements based on discomfort: An experimental study

Abstract

The increase in the incidence of work-related musculoskeletal disorders of the shoulder necessitates effective observational methods for quantifying associated risk factors. Therefore, this experimental study aimed to investigate the effects of shoulder flexion, repetition, and external load on discomfort and to compare six observational techniques for assessing shoulder postural loading: Hand Arm Risk Assessment Method, Assessment of Repetitive Tasks of the upper limbs, Quick Exposure Check, Occupational Repetitive Action, Rapid Upper Limb Assessment, and Loading on the Entire Body Assessment (LEBA). Based on the literature, this study summarized the characteristics of these techniques regarding assessment factors, body side assessed, risk levels, strengths, and limitations. An empirical investigation was conducted for measuring discomfort according to shoulder flexion, repetition, and external load in 16 young adults. The analysis revealed that the three independent variables of shoulder flexion, repetition, and external load significantly affected discomfort and LEBA scores at α = 0.01. Among the six methods, the LEBA score was the most strongly correlated with discomfort, and biomechanical measures of compressive force at the L5/S1 and moment at the shoulder. The LEBA also assessed the highest risk levels for the 27 experimental treatments. Although the LEBA is designed to evaluate whole-body postural stress, among the six methodologies, it emerged as a better option for assessing shoulder-relevant musculoskeletal loads under the study conditions.

Relevance to industry

Work-related musculoskeletal disorders of the shoulder are increasing in the industry. For preventing the disorders, quantification of shoulder postural loadings is required.