ABSTRACT
Computerized biomechanical models to predict the trunk muscle forces have been developed for many years because there is no other way directly to measure spinal loading in vivo. Most biomechanical models aimed at reducing the risk of musculoskeletal injuries have focused on the activities of the trunk musculature, which is important because trunk muscles counteract external moments imposed upon the trunk during manual materials handling (MMH) activities. The forces generated by these muscles can easily become excessive given that their moment arms between the spine are at a much shorter distance compared with the distance between the spine and the object being handled. Since these internal forces are often the primary loading components of the spine, it is extremely important to understand how the trunk muscles collectively load the spine under occupational conditions. Therefore, a desirable feature of a biomechanical model is that it should predict both the synergistic actions of the various internal forces acting upon the spine as well as the loading due to external forces.
