Abstract

The elastic characteristics of the musculo-tendinous unity constitute an important maker in the field of the performance control. The elastic characteristics of the muscle could be referred to as a ''global type'' elasticity or to a specific elasticity of the Serial Elastic Component (SEC). In fact in a movement which produces a stretching-shortening phase the mechanism of storage and release of elastic energy by the SEC would be enhanced by a musculo-tendinous unit (MTU) of optimal capacity to be stretched and optimal stiffness. A SEC with these characteris-tics would be well suited to storing elastic energy during the eccentric phase whilst also returning it as mechanical work during the concentric phase minimising the thermal-dispersion effect. The ideal stiffness of the SEC would tend towards the stretchy part of the elastic continuum. On the contrary a greater stiffness of the MTU would be significatively correlated to the concentric and isometric performance. Nevertheless these requisite could be strongly influenced from the specificity of the advised performance. The purpose of this study was to determine and to compare the SEC elastic characteristics in two different groups of athletes. The first group was composed of 7 country runners of national level (CRG) whose age, weight and height were respectively 20.2±2.4 (average ± SD) years, 70.1±6.2 kg and 183.7±4.2 cm, the second group was composed of 7 sprinters of national level as well (SG) whose age, weight and height were respectively 21.8±2.5 years, 73.5±8.2 kg and 179.2±4.6 cm. The musculo-tendinous stiffness of crural triceps and femoral quadriceps was calculated by means of a new test, this allows the calculation for the times of contact and flight recorded during a jump test efected on an electronic mat using the following formula: kN (N / m x kg) = Pi x (T(v)+T(c)) / (T(c x c) x ((T(v)+T(c) / Pi) - T(c)/4)). Were T(v) was the flight time and T(c) was the contact time recorded on the electronic mat. Additionally the elastic characteristics of the legs muscular system have been correlated with the equilibrium abilities. The equilibrium abilities have been studied using an oscillating board with mobile fulcrum (Delos Equilibrium Board) connected to a computer. This apparatus allowed the data acquisition of the board inclination degrees with a sampling frequency of 100 Hz. The sprinters have presented a greater stiffness (81.17±21.88 versus 55.51±12.62 N/m/Kg, p<0.05) of the femoral quadriceps in comparison to the country-runners, on the contrary the two groups didn't present stiffness differences concerning the crural triceps (460.55±53.02 versus 462.88±113.43 N/m/Kg). These results could be explained by the different muscular patterns required during the specific activity in the two groups of athletes. On the contrary the equilibrium abilities have resulted independent from the muscular system elastic property. This results confirms that the equilibrium ability must be interpreted chiefly in relationship to the optimal management of the coordination abilities. Verf.-Referat