Biomechanical analysis based on a full-body musculoskeletal model for evaluating the effect of a passive lower-limb assistive device on lumbar load

Abstract

A passive lower-limb assistive device that supports standing work has been developed to reduce lower limb loads in workers. The device effectively prevents lower limb musculoskeletal disorders such as osteoarthritis and contributes to the improvement of occupational health. However, previous studies have not clarified lumbar load when wearing the device. The present study investigated the effect of a passive lower-limb assistive device on lumbar load and verified the effectiveness of biomechanical analysis for evaluating the physical load while wearing the device. Twelve healthy male participants performed an assembly task under three conditions: standing and high and low sitting while wearing the device. We mainly analyzed the joint torque and joint compression force (JCF) computed using a full-body musculoskeletal model based on measurements obtained from a motion capture system and force platform. The present study concluded that the lumbar load increased when wearing the device because the lumbar joint torque was significantly larger than that for standing. In addition, the biomechanical analysis has the advantage of evaluating the lumbar load when wearing the device because the current method of analyzing muscular activity is not able to evaluate the lumbar load including the effects of passive resistance, such as those generated by ligament force and abdominal pressure. Furthermore, the present method is able to simultaneously investigate physical loads in the lower limb and neck joint based on the analysis of the JCFs in the lower limb and the neck joint torque, which is effective as an analytical method for the effect of the passive lower-limb assistive device on the risk of musculoskeletal disorders.