A MEASUREMENT CHAIN APPLICABLE IN THE BIOMECHANICS OF SHOOTING SPORTS

Abstract

SONIC DIGITIZING is a new and very precise method for kinematic analysis In shooting sports (Gianikellis et al. 1992). The purpose of this study was to Improve the technical characteristics and capabilities of this method, also its applicability for complete Biomechanical Analysis in movements of high precision and shooting sports Now, the sampling rate 1s 66 6 Hz (Instead of the 37 Hz previously obtained frequency) divided by the number of emitters placed in an active volume of a cube with two meters side length. The Sonic Digitizer would be optionally faster working In smaller volumes (up to 100 Hz) In this way, we can use more ultrasound emitters sampling them within an appropriate rate for this class of motor patterns (according to Shannon s theorem). Also, the 3-d~mens~onaclo ordinates of the emitters are calculated respect to the system of reference by means of a Newton-Raphson's optimization algorithm This algorithm improves the precision of the system The calculated standard deviation for the coordinates X, Y, Z 1s 0 1 mm (Instead of the 0.15 mm previously calculated standard deviation). Since sonic digitizer is a multiplexing system, we have implemented an interpolation and smoothing of data algorithm to have simultaneously the coordinates of all anatomical points of Interest. This algorithm 1s based on the Natural B-Spline functions according to the True Predicted Mean-Squared Error criterion (Woltring 1986) After this, we can easily obtain the velocities and accelerations of the anatomical markers of interest Finally, the measurement chain is completed with a strain-gauge Force Platform (DINASCAN) synchronized with the Sonic Digitizer. In this way, there IS the possibility to carry out stabilometric studies treating the variability of the coordinates of the Centre of Pressure during the aiming process. The resultant parameters of the kinematic and stabilometric analysis are referred to a common temporal base up to the Instant of the triggering which IS detected by means of a microphone sensor