Date of Award


Publication Type

Master Thesis

Degree Name




First Advisor

Potvin, Jim,


Health Sciences, Occupational Health and Safety.




The purpose of this study was to develop an optimization model of the spine that, incorporating a measure of spinal stability as a constraint, allowed for realistic predictions of trunk muscle and spine compression forces. A 3-dimensional, 52 muscle, single joint model of the lumbar spine was developed and tested in situations of pure trunk flexor and lateral bend moments. Spinal stability, about each anatomical axis, was calculated at the L4/L5 spinal joint. Estimates of the optimal level of spinal stability, in a given loading situation, obtained through the use of regression equations developed from experimental findings, were utilized as constraints in the optimization model. Two separate optimization cost functions were tested: (1) minimization of the sum of the cubed trunk muscle forces; (2) minimization of the intervetebral force at the L4/L5 joint level. The addition of spinal stability measures, about each anatomical axis, as constraints in the optimization model, caused significantly improved estimates of the compressive forces acting on the spine, as well as improved prediction of trunk muscle forces as a whole. Furthermore, the addition of stability constraints allowed the model to predict activity in muscles functioning as pure antagonists to the applied external moment, a first for optimization models of the spine. Thus, it is concluded that spinal stability plays a vital role in dictating the recruitment patterns of trunk muscles. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2003 .B76. Source: Masters Abstracts International, Volume: 42-02, page: 0572. Adviser: Jim Potvin. Thesis (M.H.K.)--University of Windsor (Canada), 2003.