Faisal Alessa

Date of Graduation


Document Type


Degree Type



Statler College of Engineering and Mineral Resources


Industrial and Managements Systems Engineering

Committee Chair

Xiaopeng Ning

Committee Co-Chair

Ashish Nimbarte

Committee Member

Xiaopeng Ning

Committee Member

Gary L Winn


Low back pain (LBP) is among the most prevalent occupational health problems worldwide and is a leading cause of lost work days. Previous studies have suggested that static prolonged trunk bending could generate lumbar muscle fatigue and introduce creep to the lumbar posterior tissues. Such physical changes could lead to alterations to the lumbar active and passive tissue sharing mechanism and also elevate spinal loading, which is highly associated with the risk of LBP. In the past, most occupational ergonomic studies focused on the instantaneous spine biomechanical responses during task performance. A few studies assessed the changes of spine biomechanics due to spinal tissue creep (introduced by prolonged trunk full flexion) and lumbar muscle fatigue (introduced by prolonged or repetitive trunk bending). However, the dynamic changes of lumbar and trunk postures and spinal tissue loadings during the performance of relatively short-term trunk bending tasks are still unclear. Therefore, the purpose of the current study was to investigate the changes of lumbar biomechanics during short-term, sustained trunk bending.;In the present study, fifteen participants performed short-term (40 seconds) static trunk bending tasks in two different trunk postures (30° or 60°) with two different hand load levels (0 or 15lbs). Results of the current study revealed significant reduction of lumbar muscle activities during the course of task performance. This change was coupled with significant increase of lumbar flexion angle and lumbar passive moment. Such increase of lumbar passive tissue loading could help relief/delay lumbar muscle fatigue by compensating the reduced lumber active tissue loading. Findings of this study suggest that, during the performance of sustained trunk bending, there is an internal mechanism to shift loading from lumbar active tissues to passive tissues by increasing the lumbar flexion. This mechanism is beneficial in reducing the amount of lumbar muscle fatigue; however, lumbar passive tissue creep could be generated at a faster rate.