SAFETY CONSEDERATIONS FOR GYMNASTICS LANDING MATS -PROPERTIES, CONSTRUCTION, STANDARDS AND USE

Abstract

The gymnast is faced with the necessity to land This means that complex movements must be transformed to a controlled, stable and safe landing position. The largest part of the energy is absorbed by negative dynamic work of the leg extensors. However, the human body is not well suited to deal with the high impact forces acting in the first 20 to 40 ms after touch-down Hence a synergistic system is needed that reduces the initial peak forces without negative effects on the remaining landing phase. 0 Soft mats do not solve the problem They aFe constructed for large surface type landings. As soon as the gymnast performs a controlled landing, the soft mat is excessively compressed and fixates the feet This can cause serious injuries such as torsional fractures. The construction of good landing mats requires experience and research effort. Prototypes are tested mechanically and ' in real life ' by gymnasts Points that deserve attention include the force - deformation curve, frictional characteristics, properties of the various layers of the sandwich and stability of the edges. A wedge-shaped insert resulted in the best corner and edge stabilization. The FIG uses standards and procedures that were adopted by other Standardizing Committees. A 20 kg mass instrumented with an accelerometer slides down a 0,8m rod. The acceleration-time data is then used to compute the decelerating force, the indention of the mat and the height of rebound Based on available mats standards were set. The authors present data to support the notion, that the norms are not consistent nor valid. The viscoelastic properties of the foams create a velocity dependency that cannot be neglected. Friction of the testing apparatus is only accounted for in the height dropped - not the rebound The procedures for standardization and the absolute norms should be reconsidered and brought ' up to date ' The total energy of the testing procedure is too low. The rebound height is specific to the test conditions and of little value for the assessment. The force-displacement curve could give a better indication of the mat's spectrum There is no reason to limit the penetration - provided that the mat does not ' bottom out ' or the feet are fwed in a narrow hole Landing mats should absorb the initial peak force. This requires large deformation. To avoid foot fixation a force distributing layer near the top of the mat is needed that guarantees the necessary surface elasticity