The effectiveness of exercise has been increasingly studied as exercise has been popular for the improvement of physical performance and rehabilitation of lumbar spine. A variety of exercises have been used to reduce back pain or spinal degeneration. However, there are no studies to determine effects of exercise on lumbar spine kinematics, including lumbar-pelvic coordination and instantaneous axis of rotation. The current study aimed to examine these lumbar spine kinematical changes due to exercise and therapy. We hypothesized that exercise and therapy will affect the changes of lumbar spine kinematics. Lumbar-Pelvic motions were recorded from 86 healthy subjects while performing lifting and lowering tasks of 10% and 25% of body weight. The influence of exercise was quantified from coefficients of curve-fitting for pelvic and lumbar angles. There was a significant difference (p<0.05) for the range of lumbar motion (distribution, D) between the control group and the cardiovascular exercise group after 12-week program. However, there was no significance for lumbar-pelvic coordination, C. A second study was performed to investigate the changes of instantaneous axis of rotation (IAR) at which trunk angle reached 25º. Results indicated that a superior-inferior location of IAR was significantly (p<0.05) modified by the cardiovascular exercise after 12 weeks, but there was no significant effectiveness of the physical therapy exercise. Finding of lumbar spine kinematics during lifting and lowering a weight which are the most popular manual handling activities may provide great understanding of the exercise effectiveness. Future studies are recommended to assess whether the changes of lumbar spine kinematics lead to the decrease instances of lumbar spine injuries or low back pain. / Master of Science

Musculoskeletal computational modeling is a versatile and effective tool which may be used to study joint mechanics, examine muscle and ligament function, and simulate surgical reconstructive procedures. While injury to the elbow joint can be significantly debilitating, questions still remain regarding its normal, pathologic, and repaired behavior. Biomechanical models of the elbow have been developed, but all have assumed fixed joint axes of rotation and ignored the effects of ligaments. Therefore, the objective of this thesis was to develop and validate a computational model of the elbow joint whereby joint kinematics are dictated by three-dimensional bony geometry contact, ligamentous constraints, and muscle loading.Accurate three-dimensional bone geometry was generated by acquiring CT scans, segmenting the images to isolate skeletal features, and fitting surfaces to the segmented data. Ligaments were modeled as tension-only linear springs, and muscle were represented as force vectors with discrete attachment points. Bone contact was modeled by a routine which applied a normal force at points of penetration, with a force magnitude being a function of penetration depth. A rigid body dynamics simulator was used to predict the model's behavior under particular external loading conditions.The computational model was validated by simulating past experimental investigations and comparing results. Passive flexion-extension range of motion predicted by the model correlated exceptionally well with reported values. Bony and ligamentous structures responsible for enforcing motion limits also agreed with past observations. The model's varus stability as a function of elbow flexion and coronoid process resection was also investigated. The trends predicted by the model matched those of the associated cadaver study.This thesis successfully developed an accurate musculoskeletal computational model of the elbow joint complex. While the model may now be used in a predictive manner, further refinements may expand its applicability. These include accounting for the interference between soft tissue and bone, and representing the dynamic behavior of muscles.