Reliability, Construct Validity and Interpretability of the Brazilian version of the Rapid Upper Limb Assessment (RULA) and Strain Index (SI).

Background: There are very few observational methods for analysis of biomechanical exposure available in Brazilian-Portuguese.

Objective: This study aimed to cross-culturally adapt and test the measurement properties of the Rapid Upper Limb Assessment (RULA) and Strain Index (SI).

Methods: The cross-cultural adaptation and measurement properties test were established according to Beaton et al. and COSMIN guidelines, respectively. Several tasks that required static posture and/or repetitive motion of upper limbs were evaluated (n>100).

Results: The intra-raters' reliability for the RULA ranged from poor to almost perfect (k: 0.00-0.93), and SI from poor to excellent (ICC: 0.05-0.99). The inter-raters' reliability was very poor for RULA (k: -0.12 to 0.13) and ranged from very poor to moderate for SI (ICC: 0.00-0.53). The agreement was good for RULA (75-100% intra-raters, and 42.24-100% inter-raters) and to SI (EPM: -1.03% to 1.97%; intra-raters, and -0.17% to 1.51% inter-raters). The internal consistency was appropriate for RULA (α=0.88), and low for SI (α=0.65). Moderate construct validity were observed between RULA and SI, in wrist/hand-wrist posture (rho: 0.61) and strength/intensity of exertion (rho: 0.39).

Conclusion: The adapted versions of the RULA and SI presented semantic and cultural equivalence for the Brazilian Portuguese. The RULA and SI had reliability estimates ranged from very poor to almost perfect. The internal consistency for RULA was better than the SI. The correlation between methods was moderate only of muscle request/movement repetition. Previous training is mandatory to use of observations methods for biomechanical exposure assessment, although it does not guarantee good reproducibility of these measures.