DEVELOPING A NOVEL MODEL TO MEASURE DYNAMIC JOINT STIFFNESS OF L4/L5 JOINTS IN HUMAN LUMBAR SPINES USING AN INVERSE DYNAMIC APPROACH

Abstract

Joint stiffness has been claimed as the main component providing stability to human spines during different daily activities. As a result, researchers have developed various models to calculate spinal joint stiffness during performance of different functional tasks. However, to date, the models in the literature have estimated spinal joint stiffness using only discrete measures during dynamic tasks, and do not consider temporal changes. Therefore, the main objective of this thesis was to address this gap in the literature by developing equations to estimate dynamic L4/L5 joint stiffness in the sagittal plane, and to use these equations to estimate sagittal plane dynamic L4/L5 joint stiffness during two different controlled dynamic tasks under two different conditions (performing the tasks with and without abdominal hollowing (AH)). Ten healthy men between the age of 20 and 30 years old with no history of low back pain were recruited to perform two modified levels of Trunk Stability Test protocol (levels 1 and 3) with and without AH. The results of this study revealed that AH resulted in significantly (p < 0.05) higher dynamic L4/L5 joint stiffness and lower L4/L5 joint angle range of motion, but no significant effect on the sagittal plane L4/L5 joint moments.