An ergonomic assessment of upper limb musculoskeletal risk factors using revised strain index (RSI) and threshold limit value for hand activity level (TLV- HAL) in hand-swen shoe workers

Repetitive movements and overexertion during occupational activities can lead to musculoskeletal disorders in the upper limbs. The aim of this study was to assess the ergonomic risk factors of the upper limb extremities using modified strain index (RSI) and threshold limit value for hand activity level (TLV-HAL) methods in hand-swen shoe workers in Tabriz city.
The ergonomic exposure of 218 hand-swen shoe workers was assessed by RSI and TLV-HAL method in this cross-sectional study. Direct observation and videotaping of the work-cycles were used to calculate the study variables. Data were analyzed by descriptive and analytical methods such as one-way ANOVA, Spearman correlation, and Kappa statistics.
Two hundred and eighteen workers were recruited involved in three tasks including preparation (69), sewing (63) and shoemaking (86). The average score of RSI for sewing, preparation, and shoemaking workers was 9.30, 46.10, 95.91, respectively while the average score of TLV-HAL for these tasks was 0.27, 0.81 and 1.70, respectively. Almost all workers in preparation and shoemaking tasks were categorized in the hazardous level of exposure while sewing workers were categorized in the safe exposure level. The scores of TLV-HAL had a significant and high correlation with the scores of RSI.
According to the results, the workers in preparation and shoemaking tasks were at a higher risk of upper limbs musculoskeletal disorders due to repetitive actions and overexertion. Therefore, ergonomic interventions are suggested for these tasks to reduce the level of these risk factors.