INTRODUCTION: Aim of the work was the acquisition and analysis of EMG Signals on the legs and the back of an elite athlete during Slalom courses in a snow field. The purpose of the investigation was to develop a reliable method for the acquisition of EMG Signals in the slopes that could be synchronously correlated to the pole passing instants, the skier body posture, the ski angle of attack and the loading actions on the ski. These data are necessary for the biomechanical evaluation of the skiing technique (Zeglinksy et al,1998), the correlation with the ski loading patterns and the functional evaluation of optimised skiing equipments (Muller & Schwameder,2003). METHOD: A portable data acquisition unit PocketEMG® from BTS-ltaly was used for data collection in the field. The unit is based on a PDA System and allows to measure 16 EMG channels at 10 kHz sampling rate; the unit can support 4 Biometrics® goniometers and was customized to collect also bridge sensors like strain channels and accelerometers. The dimensions (145x95x20 mm) and weight (0.3 kg) of the PocketEMG® allow to place it easily in a pocket of the ski suite without influencing the skier behaviour in the slope. A set of accelerometers was placed on the leg composite protections and recorded with the 10 EMG Signals in order to have the timing with respect to the pole passing. Two inertial platforms X-sense Mti were applied to the skis and synchronously recorded at 100 Hz (Figure 1). Three elite skiers were involved in the study, wearing racing slalom skis with different tuning conditions. Several courses of Special Slalom were performed on a slope of known shape _and orientation. RESULTS & DISCUSSION: The EMG Signals were normalised to Maximum Voluntary Contractions (MVC) and analysed between the pole passages. For a given track and ski tuning, the testers were compared in terms of timing pattern at the poles and of intensity of EMG activation at the different muscles. The EMG activities recorded during two courses with two tuning conditions of the skis were compared using paired t-tests within each tester in order to evaluate the correlation with the testers subjective evaluations of the two conditions. CONCLUSION: The work allowed to develop an integrated non-invasive EMG data acquisition System suitable for technical evaluation of the athletes and of the skiing equipments performances.
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