In the present investigation, a comprehensive set of reliable data for the
human spine has been established, and a useful aggregation and analysis of the data
has also been carried out. Data obtained has been presented in tabulated and
graphical forms to allow easy comparison with other researchers' data. The new
accurate data obtained has been used in the construction of a kidney-shaped model of
a functional spinal unit which has been subjected to finite element testing that
resulted in very good agreement with the results of other published models.
A computer-based formulation for the dynamic analysis of an' inertia-variant
spatial human body system has also been developed. The human body system is
modelled as a multi-body system consisting of interconnected rigid, elastic and
visco-elastic components. Each of these components is allowed to undergo large
angular rotations. A linear visco-elastic Kelvin-Viogt model is employed whereby
stress is assumed to be proportional to the time rate of strain. The focus in this work
is placed on the analysis and diagnosis of lumbar and lumbo-sacral back problems
associated with lifting activities. All human links are treated as rigid, while the entire
lumbar spine is considered to be elastic. Flexibility of the lumbar spine is introduced
into the mathematical model using a set of short and stubby finite elements which
describe the behavior of the vertebrae and discs at the lumbar region and which
accounts for both geometric and inertia nonlinearities.
The implementation of the model and analysis of results has been limited to
the two-dimensional case in the sagittal plane in recognition of the well known
difficulties encountered in solving human body systems. Health and safety issues in
material handling are currently receiving the concern of many researchers as well as
manufacturing companies. Therefore, two case studies were carried to establish the
importance, accuracy and validity of the model developed in this thesis. A two dimensional
lifting task with a flexible lumbar spine formed the first case study
whilst the second was a pushing task.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.