A biomechanical model to analyze loading in the lumbosacral joint

A study on the dynamic loading in the lumbosacral joint during level walking was carried out. A simplified biomechanical model based on four single muscle equivalents and five free body segments; namely the foot, shank, thigh, pelvis and HAT (head, arms and trunk) was developed. In this model, the forces and moments acting on the lumbar spine come from body-segment mass, movements of the trunk and external loads. These external forces and their moments must be equilibrated by internal forces; that is, contributions from the erector spinae and rectus abdominus muscle group and abdominal pressures from within the trunk. This study was performed on five male subjects. The subjects were instructed to walk on a level 12 m walkway in the motion analysis laboratory of the National University of Singapore. Results from this study showed that the peak loading on the lumbosacral joint was in the range of 1.8 to 2.7 times body weight, during the activity of normal level walking.