The body's equilibrium is possible thanks to the integration of skeletal structure, vertebrae, ligaments and muscles to form one functional unity.
The forces which determine posture are composed of two complementary systems, the ligamentary and the muscular systems, which together determine a dynamic act of balance.
The ligaments operate mainly against the viseo-hydraulic pressure of the nucleus pulposus and bind the vertebral bodies together, whereas the muscles exhibit an antigravity function and support spinal stability.
A mathematical model based on a mixed theory of directed and oriented curves is proposed. Through this model it is possible to develop an exact theory governing the deformation of the ligamentous spine. This theory should be universal in the sense that it can be used to study the spine in any of its environments.
Zusammenfassung. Die aufrechte K6rperhaltung wird physikalisch durch das oss~re, das muskulgre und ligament~re Kr/iftesystem gekennzeichnet. Alle diese Systeme streben in der NormMhaltung ein Gleichgewicht an.
Es wird aufgrund einer einfachen, nieht linearen Theorie ein mathematisches Modell gezeigt, welches das meehanische Verhalten des osteoligamentgren Anteils der Wirbels/~ule auf Lgngs-und Schubdehnung, Biegung und Verdrehungsdeformation darstellt.