Stability of the shoulder, more precisely the glenohumeral joint, can only be achieved in case of healthy and well coordinated muscular activity in the upper limb. Degenerative deseases like osteoarthritis, muscle deficiencies or injuries can lead to instability problems of the humeral head. To analyse human shoulder stability, numerical models have been developped at the LBO that allow the simulation of humeral head translation in the glenoid cavity. As muscles play an important role, the aim of that project is to refine the muscle modelling by developping a new 3D muscle model. This new muscle model will then be included into an existing shoulder model. The first part of this project is to study muscle anatomy, physiology and existing constitutive laws. In a second step, the modelling of the muscle and the implementation of appropriate user subroutines will be done in Abaqus. Basic knowledge of finite element analyses and programming are recommended.