PRESSURE DISTRIBUTION UNDER THE FOOT DURING TAKE OFF IN TRAMPOLINING

Abstract

In the past, biomechanical investigations in trampolining were mostly concerned with the aerial movements, whereas the take off was rarely in the focus of interest. One reason for this lack may be the difficulties in performing dynamic measurements during the take off. The development of new pressure measurement devices encourages their use also in trampolining. At first two questions should be answered with the aid of this instrumentation. 1. Which differences in the pressure distribution occur between beginners and skilled gymnasts? 2. Are there any basic differences in the pressure distribution at take off between exercises with and without moment of impulse? Methods The pressure distribution was determined using F-SCAN, a resistive based in-shoe measurement device. The insole is 0.17 mm thick and contains 960 sensors (resolution 4 sensors/cm2). The sampling rate was 50 Ha and the sampling time embraced 4 s. The sole was cut to the necessary size and put in the right gymnast shoe of the subject. The data transmission ensued via a cuff unit (m = 300 g) and a wire to a personal computer. The investigated movements included three categories of exercises: 1. straight jump, 2. forward sommersaults (single up to double), 3. backward somersaults (single up to double). As subjects sewed 2 female beginners and 5 skilled gymnasts (female and male). Results and Discussion The ratios of support time and flight time confirm the spring characteristic of a trampoline. For one subject the support time is constant and independent from the jump hight. No general differences in the pressure distribution could be found between beginners and skilled subjects. Except the straight jump, it was not possible to distinguish the different somersaults (forward - backward) in terms of pressure distribution by the use of statistical methods. But the intraindividual analysis of the exercises showed a relation between the skill and the variance of the pressure distribution. It can be concluded that the dynamic of the foot contact has always the same characteristic. The moment of impulse is produced by the movements of the upper parts of the body.