Modeling the deformation of skeletal muscle contraction

A computational framework to simulate skeletal muscle deformation during contraction is presented in this thesis. The graphical modeling of whole muscle deformation is obtained by means of a physically consistent, anatomically and physiologically accurate model. The modeling is performed at the muscle fibre and whole muscle level. The modeling of skeletal muscle at the fibre level allows for a full implementation of muscle architecture. It is well known in muscle mechanics that muscle architecture is a primary determinant of muscle function. The modeling of the muscle architecture by means of physically-based modeling may be used to improve the understanding of muscle mechanics during contraction. In the proposed computational framework, muscle contraction, and its associated internal and external deformation, is reproduced accurately by simulating the active and passive muscle fibre characteristics, and the passive muscle structure properties. The muscle model includes non-linear properties of muscle tissue, novel features in the active muscle constitutive equations, passive constitutive behaviour of the tendon with pseudo-wrinkling of the fibrous tissue, and geometric constraints that can be enforced through Lagrange multipliers. The proposed muscle model predicts fibre forces based on the principle of virtual work, along with appropriate geometric constraints using a non-linear finite element analysis. The model introduces methods to produce realistic skeletal muscle deformation to be used in computer animation applications, and to study muscle function in biomechanical applications. The model is sufficiently general to be applied in other non-linear soft tissues with different material properties. In order to demonstrate the potential applications of the model, some preliminary studies in muscle deformation are presented. In these studies, the investigation of force production, structural changes, visualization and representation at different structural levels and whole muscle deformation in skeletal muscles during contraction are performed using the cat medial gastrocnemius and the human tibialis anterior muscles. Comparisons of force production and structural changes were made between theoretically predicted and experimentally measured values. Several observations in muscle deformation during contraction were conceptually predicted by the model.