Telemetry and computer processing of accelerometric data in cross country skiing

A telemetry system is described and a package of computer programs allowing the determination of the torso acceleration in cross country skiing. The acceleration components are given by two accelerometers mounted in quasibaricentric position in the antero-posterior vertical plane. One of the accelerometers measures also the gravity component, thus allowing the determination of the mean torso inclination. The signals from the two accelerometers are fed to a PCM telemetry system and recorded on analog tape after decoding at the receiving station. The package of Fortran programs allows: 1) AD conversion at 100 Hz to avoid aliasing in the useful spectral range, limited to 20 Hz; 2) calibration and automatic reduction of the noise due to transmission synchronization losses; 3) averaging, computation of the mean torso inclination and reconstruction of the vertical and horizontal acceleration components; 4) integration of the acceleration components to give speed and displacement components and thus potential and kinetic energy variations. A synchronization signal allows the comparison of the acceleration with the cinematographic analysis of the movement.