Integrating sEMG into NIOSH protocol: a manual material handling risk assessment in the fruit and vegetable department of a supermarket

Abstract

The biomechanical risk of cashiers in the retail sector has been extensively studied in literature. Despite high back pain prevalence in this sector manual material handling (MMH), instead, seems almost ignored. The aim of our study is MMH risk assessment in a fruit and vegetable department of a supermarket. This task wasn't still investigated, to date, together with standardized protocols and instru-mental-based tools. The sizes of the shelf allowed the use of the NIOSH protocol for the low level, whereas middle and high did not allow its use due to horizontal distance that exceeded the 63 cm set by the protocol. To integrate the NIOSH pro-tocol was used surface electromyography (sEMG). The recommended weight limit (RWL) in our case, according through NIOSH liftinq equation, was 17 Kg. The maximum handled weight from the workers was 14 Kg. The maximum mean peak value while lifting 14 Kg at a low level was 40.1% of Maximum Voluntary Contraction (MVC) in the left Erector Spinae. We assumed this sEMG value to be a safety value and used as a limit for lifts at the middle and high shelf levels because the maximum handled weight of 14 Kg was lower than the 17 Kg limit calculated through the NIOSH equation for the low level. This sEMG limit was exceeded, in the middle, while lifting 14 Kg (47.8% MVC), and in the high level lifting 10 Kg (44.7% MVC), 12 Kg (50.3% MVC), and 14 Kg (57.7% MVC). Our findings show that, for the analyzed shelf and for the male working popula-tion of that supermarket, we could accept as reasonably safe handling boxes up to 14 Kg for the low level, up to 12 Kg in the middle, and up to 8 Kg in high. This study shows that the integration of different assessment tools, such sEMG and NIOSH protocol, could help to a better estimation of biomechanical risk assess-ment. The study, moreover, provided practical guidelines for the health and safety service concerning the recommended load handled on each shelf level to minimize the risk of MMH in the fruit and vegetable department.