THE STABILITY OF THE UPPER LIMB IN DIFFERENT SPORT EVENTS

Abstract

INTRODUCTION -The study of a biomechanic system will imply the use of many simplification hypothesis, approximation methods and optimisation techniques. The study of a system is extremely important due to the fact that many times our body is confronted with abnormal solicitations. In this paper we will try develop an improved analytic model that could be used for analysing the behaviour of the shoulder girdle mechanism. METHODS The shoulder girdle, according to anatomic description, presents four elements: thorax, c1aviele, scapula and humerus and next joints: sternoclavicular (SC), acromioclavicular (AC), glenohumeral (GH) and the scapulothoracic gliding plane (ST). The dimensions of these were taken from classic antropometric studies (Bart, 1957). To model the Kinematic chain the specified joints re modelled as follows: the SC, AC and GH joints as spherical joints (each of these possessing three degrees of freedom-doffs) and the ST joint as presenting 4 doffs. We would Iike to underline the fact that the definition for the number of doffs that characterise AC and SC joints reflects last hour experiments (Pronk, 1991; van der Helm, 1992, 1994; Veeger, 1992) and contradicts previous limited definitions for these joints mobilities. RESULTS -The obtained results are touching kinematic and dynamic aspects From Kinematic point of view these results respect the natural behaviour of the shoulder girdle From dynamic point of view the results are more interpretable. As concerning the system's stability, interesting conclusions were found, CONCLUSION -The presented model can be used for analysing the behaviour of this biomechanism and for predicting its comportment in the case of different sports events, especially from stability point of view REFERENCES -Rinderu, P.L, (1995). Contributions to the mechanisms analysis and synthesis in accordance to vertebrates movements. Doctoral thesis, University of Craiova, Romania. Van der Helm, F.CT, (1994). A finite element musculo-keletal shoulder mechanism, J. 27. 551-569. model of the Biomechanics