Abstract:
This thesis presents a new framework and methodology for modelling the structure and function of skeletal muscles. It incorporates an anatomical description of the macroscopic structure of the muscle, an extensive representation of the physiology of skeletal muscle tissue, and a comprehensive depiction of the functional response of skeletal muscle to both physiological and external inputs. The components of structure, physiology, and function are combined together to give the most detailed skeletal muscle model currently available. The general skeletal muscle modelling framework is demonstrated using the specific example of the human Tibialis Anterior. The physiology of skeletal muscle is represented using the Shorten et. al. cellular model [107] and the Bidomain equations [55]. The structure of the human Tibialis . Anterior muscle is represented using triquadratic-Lagrange Finite Elements, and includes information on the internal muscle fibre directions. Individual muscle fibres are explicitly represented within the muscle and are grouped into functional units ( the Motor Units) in a physiologically accurate manner. Physiological activation, or activation as a result of an applied stimulus, can be represented. Physiological data obtained from the combination of the fibre activation and the Bidomain simulation of muscle physiology are then linked, using a novel muscle constitutive law, to produce whole muscle deformation. The framework is a true multi-scale modelling framework, linking one of the most detailed skeletal muscle physiological models available to the deformation of the muscle as a whole. As a result of this detail, muscle force output profiles that replicate physiologically, and numerically obtained data, can be generated. The modelling framework has been developed to maximise versatility. It provides for the first time a multi-scale framework where such a large number of model input parameters are able to be modified to demonstrate the effect of varying muscle properties. The versatility of this modelling framework is demonstrated by building stimulation protocols, using the constraint of inverse muscle recruitment, which represent normal, physiological, muscle recruitment. It is hoped that, with further advances in knowledge concerning the mechanical behaviour of skeletal muscle, this modelling framework will be able to provide insight into the development of Functional Electrical Simulation protocols, as well as provide a tool for researchers interested in the interaction of structure and function within skeletal muscle.