A biomechanical model for predicting the compressive force exerted on L5/S1 in manual material handling by Thai youth in Thailand

Background Manual lifting tasks are a leading cause of occupational low back disorders (LBD). Objective This study aimed to predict the compressive force (CPF) at L5/S1 among young Thai lifting workers. Methods Sixty healthy Thais aged from 18 to 24, evenly divided by gender, performed repetitive lifting tasks with five different lifting frequencies (1, 2, 4, 6, and 12 lifts/minute). A three-dimension static strength prediction program (3D SSPP) was used to identify the injury risk on the low back L5/S1 using biomechanical criteria (compression and shear forces) at extreme postures. Multiple linear regression analysis (MLRA) was used to predict factors related to the CPF. Results The load weight significantly impacted the CPF at L5/S1 joint for both the lift origin and destination. Lift origin, load weight, trunk angle, body mass index (BMI), and rating of perceived exertion (RPE) significantly affected the CPF exerted at L5/S1 for lift origin ( p < 0.001). In part of the CPF for the lift destination, load weight, trunk angle, forearm angle, BMI, lifting frequency, and gender were significantly influential. The CPF at L5/S1 for the lift origin and destination in males exceeded that of females at every lifting frequency. Conclusions This study helps identify ergonomics risks and may be used to determine the proper weight load for reducing the risk of musculoskeletal injuries (MSI). Therefore, based on the findings of this study, the ergonomic training programs focusing on lifting techniques should consider to improve awareness of MSI.