The full-body lumbar spine (FBLS) model was created by combining other previously developed OpenSim models (https://simtk.org/home/lumbarspine, https://simtk.org/home/runningsim, https://simtk.org/home/lowlimbmodel09). The purpose of developing this model was to provide users with a full-body model suited for investigations involving the trunk musculature and lumbar spine.

Briefly, this model consists of 21 segments, 29 degrees-of-freedom, and 324 musculotendon tendon actuators. The five lumbar vertebrae are modeled as individual bodies, each connected by a 6 degree-of-freedom joint. Net lumbar movement is described as flexion-extension, axial rotation, and lateral bending by imposing constraint functions to each individual lumbar vertebra. The eight main muscle groups of the lumbar spine are modeled, each consisting of multiple fascicles to allow the large muscles to act in multiple directions. These trunk muscles include: rectus abdominis, external obliques, internal obliques, erector spinae, multifidus, quadratus lumborum, psoas major, and latissimus dorsi.

This model is currently suitable for running Static Optimization but is not yet suited for Computed Muscle Control (CMC). A future release of the model will be suited for CMC.

This project page will make the model freely-available to OpenSim users and include information about model development and validation procedures.