BIOMECHANICAL CONSIDERATIONS FOR A NEW DESIGN OF THE PARALLEL BARS

Abstract

The cross-sectional outline and dimensions of the wooden parallel bars are given by the FIG norm. It further states that a downward force of 1350 N applied to the middle of one bar should result in a deflection of approximately 6 cm. To date, bars are made from laminated wood with inlays designed to prevent braking. The "egg" shape is ergonomical for moves performed in suspended or supported positions and must be considered superior to round bars. Many moves performed in modem gymnastics require the bars to be opened and present a lateral or oblique loading of both or a single bar. The large deflections that result from the bar geometry are a potential cause of shoulder injuries and may be detrimental to performance. The purpose of the present study was thus to determine whether one could modify the bar in a way to make it behave (deflection-wise) as if it was round without changing the ergonomical shape or the basic material of the bars. The load-deflection characteristics for existing bars in vertical, horizontal and oblique directions was measured. On the basis of this data a simple but realistic FEM model was constructed. Simulation proved that changing the module of elasticity of the lateral bar elements should have the desired effect. More complex models were employed to determine the shape and position of the inlays. The shear stresses were computed to be below the critical values for the materials and bonding wed. . Based on these computations prototype bars were constructed using a specific technique for applying and bonding inlays of carbon fibers. Measurements verify that the aim of constructing bars with a "round" deflection diagram from an "egg-shaped" bar has been achieved through the proper combination of wood and carbon fiber inlays.