The shoulder girdle is the attachment of the upper extremity to the trunk. It consists of two bones: the scapula (shoulder blade) and the clavicle (collarbone). The scapula is a flat, triangular bone that lies over the posterior surface of the rib cage. At its upper lateral corner is a cuplike depression (the glenoid fossa) which forms a socket for the head of the humerus. The sternoclavicular joint is the only bony connection between the shoulder girdle and the trunk. The scapula is connected to the trunk indirectly through the acromioclavicular joint; otherwise, the scapula is attached to the trunk only by muscles. Morphological data, including the geometry of bones and muscles, muscle physiologicalcross-sectional area (PCSA) and the inertia tensor of the segments, were recorded in a anatomy. Each muscle element represents a muscle line of action, generating force at its attachments on the bone. Then, the behavior of the complete mechanism can be calculated by simply force equilibrium.

        Key words: position, shoulder girdle, muscle dysbalantion, model